阅读说明：本技术 具有改善的凝乳性质的凝乳酶变体 (Variants of chymosin with improved curd properties ) 是由 约翰尼斯·马腾·范丹尼布林克 马丁·伦德 J·雅各布森 萨里·夏洛特·汉森 伊本·杰普森 于 2013-05-22 设计创作，主要内容包括：本发明提供了具有改善的凝乳性质的凝乳酶变体,其制备方法,以及将其用于食品或饲料产品制造的方法。(The present invention provides chymosin variants with improved curd properties, methods for their preparation, and methods for their use in the manufacture of food or feed products.)

1. A method of making an isolated chymosin polypeptide variant comprising the steps of:

(a) the method comprises the following steps Making an alteration at one or more positions in a parent polypeptide having chymosin activity, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353; and

(b) the method comprises the following steps Preparing and isolating the altered polypeptide of step (a), thereby obtaining an isolated chymosin polypeptide variant, wherein the variant has chymosin activity;

and wherein:

(i) the method comprises the following steps The amino acid position of the parent polypeptide is determined by aligning the parent polypeptide with the polypeptide of SEQ ID No. 1 (bovine chymosin) — i.e. the polypeptide of SEQ ID No. 1 is used to determine the corresponding amino acid sequence in the parent polypeptide; and

(ii) the method comprises the following steps The parent polypeptide has at least 90% sequence identity to the mature polypeptide of SEQ ID NO. 2 from amino acid position 59 to amino acid position 381 of SEQ ID NO. 2.

2. A method of making an isolated chymosin polypeptide variant comprising the steps of:

(a) the method comprises the following steps Making an alteration at one or more positions in a parent polypeptide having chymosin activity, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to position 134; and

(b) the method comprises the following steps Preparing and isolating the altered polypeptide of step (a), thereby obtaining an isolated chymosin polypeptide variant, wherein the variant has chymosin activity;

and wherein:

(i) the method comprises the following steps The amino acid position of the parent polypeptide is determined by aligning the parent polypeptide with the polypeptide of SEQ ID No. 1 (bovine chymosin) — i.e. the polypeptide of SEQ ID No. 1 is used to determine the corresponding amino acid sequence in the parent polypeptide; and

(ii) the method comprises the following steps The parent polypeptide has at least 90% sequence identity to the mature polypeptide of SEQ ID NO. 2 from amino acid position 59 to amino acid position 381 of SEQ ID NO. 2.

3. A method of making an isolated chymosin polypeptide variant as claimed in claim 1 or 2, wherein the isolated chymosin polypeptide variant has:

chymosin activity producing a C/P ratio higher than the C/P ratio of camel chymosin comprising the mature polypeptide of SEQ ID NO: 2.

4. A method of making an isolated chymosin polypeptide variant according to any of claims 1-3, wherein the parent polypeptide is a wild type mammalian chymosin.

5. The method of making an isolated chymosin polypeptide variant of claim 4, wherein the isolated bovine chymosin polypeptide variant comprises less than 10 or NO more than 5 amino acid changes compared to the mature polypeptide of SEQ ID NO. 2.

6. The method of making an isolated chymosin polypeptide variant of claim 5, wherein the alteration is made at one or more positions in a hypervariable region of the parent polypeptide having chymosin activity.

7. The method of making an isolated chymosin polypeptide variant of claim 1, wherein the alteration comprises a substitution of at least one amino acid position and wherein the substitution is 134Q, 141E, 143F, 280I, 281V, 298E, 300R, 307D, 309W, 311I, 352L, 352Q, 353L or 353Q.

8. The method of making an isolated chymosin polypeptide variant of claim 7, wherein the substitution is H134Q, Q141E, I143F, L280I, F281V, Q298E, Q300R, N307D, G309D, G309W, L311I, Q352L, E352L, E352Q, K353L or K353Q.

9. The method of making an isolated chymosin polypeptide variant of claim 1, wherein the alteration comprises a substitution of at least one amino acid position and the substitution is:

F281V+V306I+I321L；

H134Q+I154L+D216S；

V261A+V263I+G309W+L311I+Y326F；

D156V+G309D+M314L+V317I；

H134Q+L280I+G309W；

R119Q+D156V+V375L；

Y79S+R119S+H204R；

Y79S+H134Q+Y365F+V375L；

Y194I+R213Q+G309D；

Y79S+D117N+I321L；

Y185F+D325M+E352Q；

Y79S+L224V+L311I；

S132F+H134Q+M200I+M215L+G221E；

F281V+G309W+S331Y+D337E；

D156V+G309D+M314L+V317I；

G128D+L188I+Y326F；

R119S+V241I+L280I+L311I+D325M；

R119Q+S284T+T297S+V306I+G309W

K279V+V281F；

Q298E+Q300R；

H350N+Q352E+K353L；

D307N + D309G; or

Q141E+I143F。

10. A method of making an isolated chymosin polypeptide variant as claimed in any of claims 1 to 9 wherein the parent polypeptide has at least 95% sequence identity with the mature polypeptide of SEQ ID No. 2 (camel chymosin) from amino acid position 59 to amino acid position 381 of SEQ ID No. 2.

11. An isolated chymosin polypeptide variant obtained by the method of any one of claims 1 to 10.

12. An isolated chymosin polypeptide variant comprising:

(a) the method comprises the following steps An alteration at one or more positions in a parent polypeptide having chymosin activity, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353; and

(b) the method comprises the following steps Wherein the variant has chymosin activity;

and wherein:

(i) the method comprises the following steps The amino acid position of the parent polypeptide is determined by aligning the parent polypeptide with the polypeptide of SEQ ID No. 1 (bovine chymosin) — i.e. the polypeptide of SEQ ID No. 1 is used to determine the corresponding amino acid sequence in the parent polypeptide; and

(ii) the method comprises the following steps The parent polypeptide has at least 90% sequence identity to a mature polypeptide of SEQ ID NO:1 (bovine chymosin) from amino acid position 59 to amino acid position 381 of SEQ ID NO: 1; and

(iii) the method comprises the following steps The isolated variant polypeptide has less than 100% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin), an

Wherein the isolated variant has chymosin activity that produces a C/P ratio higher than the C/P ratio of bovine chymosin comprising the mature polypeptide of SEQ ID NO: 1.

13. An isolated chymosin polypeptide variant comprising:

(a) the method comprises the following steps An alteration at one or more positions in a parent polypeptide having chymosin activity, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to position 134; and

(b) the method comprises the following steps Wherein the variant has chymosin activity;

and wherein:

(i) the method comprises the following steps The amino acid position of the parent polypeptide is determined by aligning the parent polypeptide with the polypeptide of SEQ ID No. 1 (bovine chymosin) — i.e. the polypeptide of SEQ ID No. 1 is used to determine the corresponding amino acid sequence in the parent polypeptide; and

(ii) the method comprises the following steps The parent polypeptide has at least 90% sequence identity to a mature polypeptide of SEQ ID NO:1 (bovine chymosin) from amino acid position 59 to amino acid position 381 of SEQ ID NO: 1; and

(iii) the method comprises the following steps The isolated variant polypeptide has less than 100% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin), an

Wherein the isolated variant has chymosin activity that produces a C/P ratio higher than the C/P ratio of bovine chymosin comprising the mature polypeptide of SEQ ID NO: 1.

14. The isolated chymosin polypeptide variant of claim 12 or 13, wherein the parent polypeptide has at least 97% sequence identity to the mature polypeptide of seq id No. 1 (bovine chymosin); and

wherein the isolated bovine chymosin variant comprises less than 10 or NO more than 5 amino acid changes (e.g., substitutions) as compared to the mature polypeptide of SEQ ID NO:1 (bovine chymosin).

15. The isolated chymosin polypeptide variant of claim 14, wherein the parent polypeptide is a wild-type mammalian chymosin.

16. The isolated chymosin polypeptide variant of claim 15, wherein the alteration is made at one or more positions in a hypervariable region of a parent polypeptide having chymosin activity.

17. The isolated chymosin polypeptide variant of claim 12, wherein the alteration comprises a substitution of at least one amino acid position and wherein the substitution is D117N, H134Q, Q141E, I143F, D156V, V241I, V279M, L280I, F281V, Q298E, Q300R, N307D, G309D, G309W, L311I, D325M, H350N, Q352L, E352L, E352Q, K353L or K353Q.

18. The isolated chymosin polypeptide variant of claim 12, wherein the alteration comprises a substitution of at least one amino acid position and wherein the substitution is:

F281V+V306I+I321L；

H134Q+I154L+D216S；

V261A+V263I+G309W+L311I+Y326F；

D156V+G309D+M314L+V317I；

H134Q+L280I+G309W；

R119Q+D156V+V375L；

Y79S+R119S+H204R；

Y79S+H134Q+Y365F+V375L；

Y194I+R213Q+G309D；

Y79S+D117N+I321L；

Y185F+D325M+E352Q；

Y79S+L224V+L311I；

S132F+H134Q+M200I+M215L+G221E；

F281V+G309W+S331Y+D337E；

D156V+G309D+M314L+V317I；

G128D+L188I+Y326F；

R119S+V241I+L280I+L311I+D325M；

R119Q+S284T+T297S+V306I+G309W

K279V+V281F；

Q298E+Q300R；

H350N+Q352E+K353L；

D307N + D309G; or

Q141E+I143F。

19. An isolated chymosin polypeptide variant comprising:

(a) the method comprises the following steps An alteration at one or more positions in a parent polypeptide having chymosin activity, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353; and

(b) the method comprises the following steps Wherein the variant has chymosin activity;

and wherein:

(i) the method comprises the following steps The amino acid position of the parent polypeptide is determined by aligning the parent polypeptide with the polypeptide of SEQ ID No. 1 (bovine chymosin) — i.e. the polypeptide of SEQ ID No. 1 is used to determine the corresponding amino acid sequence in the parent polypeptide; and

(ii) the method comprises the following steps Said parent polypeptide having at least 90% sequence identity to a mature polypeptide of SEQ ID NO. 2 (camelid chymosin) from amino acid position 59 to amino acid position 381 of SEQ ID NO. 2; and

(iii) the method comprises the following steps The isolated variant polypeptide has less than 100% sequence identity to the mature polypeptide of SEQ ID NO:2 (camelid chymosin); and

wherein the isolated variant has chymosin activity that produces a C/P ratio higher than the C/P ratio of a camelid chymosin comprising a mature polypeptide of SEQ ID NO: 2.

20. An isolated chymosin polypeptide variant comprising:

(a) the method comprises the following steps An alteration at one or more positions in a parent polypeptide having chymosin activity, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to position 134; and

(b) the method comprises the following steps Wherein the variant has chymosin activity;

and wherein:

(i) the method comprises the following steps The amino acid position of the parent polypeptide is determined by aligning the parent polypeptide with the polypeptide of SEQ ID No. 1 (bovine chymosin) — i.e. the polypeptide of SEQ ID No. 1 is used to determine the corresponding amino acid sequence in the parent polypeptide; and

(ii) the method comprises the following steps Said parent polypeptide having at least 90% sequence identity to a mature polypeptide of SEQ ID NO. 2 (camelid chymosin) from amino acid position 59 to amino acid position 381 of SEQ ID NO. 2; and

(iii) the method comprises the following steps The isolated variant polypeptide has less than 100% sequence identity to the mature polypeptide of SEQ ID NO:2 (camelid chymosin); and

wherein the isolated variant has chymosin activity that produces a C/P ratio higher than the C/P ratio of a camelid chymosin comprising a mature polypeptide of SEQ ID NO: 2.

21. The isolated chymosin polypeptide variant of claim 19 or 20, wherein the parent polypeptide is a wild-type mammalian chymosin.

22. The isolated chymosin polypeptide variant of claim 21, wherein the isolated bovine chymosin variant comprises less than 10 or NO more than 5 amino acid changes compared to the mature polypeptide of SEQ ID NO: 2.

23. The isolated chymosin polypeptide variant of claim 22, wherein the alteration is made at one or more positions in a hypervariable region of a parent polypeptide having chymosin activity.

24. The isolated chymosin polypeptide variant of claim 19, wherein the alteration comprises a substitution of at least one amino acid position and wherein the substitution is:

F281V+V306I+I321L；

H134Q+I154L+D216S；

V261A+V263I+G309W+L311I+Y326F；

D156V+G309D+M314L+V317I；

H134Q+L280I+G309W；

R119Q+D156V+V375L；

Y79S+R119S+H204R；

Y79S+H134Q+Y365F+V375L；

Y194I+R213Q+G309D；

Y79S+D117N+I321L；

Y185F+D325M+E352Q；

Y79S+L224V+L311I；

S132F+H134Q+M200I+M215L+G221E；

F281V+G309W+S331Y+D337E；

D156V+G309D+M314L+V317I；

G128D+L188I+Y326F；

R119S+V241I+L280I+L311I+D325M；

R119Q+S284T+T297S+V306I+G309W

K279V+V281F；

Q298E+Q300R；

H350N+Q352E+K353L；

D307N + D309G; or

Q141E+I143F。

25. A method of manufacturing a food or feed product comprising adding an effective amount of the isolated chymosin polypeptide variant of any of claims 11 to 24 to a food or feed ingredient and performing further manufacturing steps to obtain the food or feed product; and

wherein the product is a milk-based product and wherein the method comprises adding an effective amount of the isolated chymosin polypeptide variant of any one of claims 11 to 24 to milk and performing further manufacturing steps to obtain the milk-based product; and

wherein the milk is soybean milk, sheep milk, goat milk, buffalo milk, yak milk, alpaca milk, camel milk or cow milk; and

wherein the milk-based product is a fermented dairy product, quark or cheese.

Technical Field

The present invention relates to chymosin variants with improved curd properties.

Background

Enzymatic coagulation of milk using chymosin enzymes (e.g. chymosin and pepsin) is one of the most important processes in cheese production. Enzymatic milk coagulation is a two-stage process: a first stage in which proteolytic, chymosin or pepsin attacks the kappa-casein, resulting in a metastable state of casein micellar structure and a second stage in which the milk subsequently coagulates and forms a coagulum.

Chymosin (EC 3.4.23.4) and pepsin (EC 3.4.23.1), the chymosin class of the mammalian stomach, are aspartic proteases belonging to a large class of peptidases.

When produced in gastric mucosal cells, chymosin and pepsin are present as non-enzymatically active chymotrypsinogen precursors and pepsinogen precursors, respectively. When chymosin is secreted, the N-terminal peptide fragment, i.e.the fragment precursor (signal peptide), is cleaved off to yield a chymosin comprising a pro-fragment. Chymosin is an enzyme in a substantially inactive form, but is activated to active chymosin under acidic conditions by autocatalytic removal of the pro-fragment. This activation occurs in vivo in the gastric lumen under suitable pH conditions or in vitro under acidic conditions.

The structural and functional characteristics of cattle (i.e., Bos Taurus), the chymosine precursors, chymosine, and chymosin have been studied extensively. The precursor portion of the chymotrypsinogen precursor molecule (pre-part) comprises 16aa residues, the corresponding procymbiont portion of chymotrypsinogen (pro-part) has a length of 42aa residues. Active bovine chymosin comprises 323aa, a mixture of two active forms a and B.

Chymosin is naturally produced in mammalian species such as cows, camels, goats, buffalos, sheep, pigs, humans, monkeys and rats.

Bovine chymosin has been commercially available for many years in the dairy industry.

WO02/36752A2(Chr. Hansen) describes the recombinant manufacture of camelid chymosin.

The references listed immediately below may be considered in the context of the present invention as references describing mutants of chymosin:

suzuki et al Site directed mutagenesis functional distribution Thr218, Lys220 and Asp304 in chymosin (Site directed mutagenesis revealed the functional distribution of Thr218, Lys220 and Asp304 in chymosin), Protein Engineering, Vol.4, 1990, 1 month, pages 69-71;

suzuki et al Alteration of catalytic properties of chymosin by site-directed mutagenesis, Protein Engineering, Vol.2, 5.1989, page 563-;

van den Brink et al, incorporated production of chymosin by glycosylation, Journal of biotechnology, Vol.125, 9.2006, page 304-;

(iii) -Pitts et al Expression and characterization of the chymosin pH optima products in Tricoderma reesei (Expression and characterization of the most suitable mutants of chymosin pH produced in Trichoderma reesei), Journal of biotechnology, Vol.28, 3 months 1993, pages 69-83;

M.G.Williams et al, Mutagenesis, biochemical characterization and X-ray structural analysis of point mutants of bovine chymosin, Protein engineering design and selection, Vol.10, 9.1997, p.991-;

strop et al, Engineering enzyme subsite specificity: preparation, kinetic characterization, and x-ray analysis at 2.0ANG resolution of Val111phe localized calf chrome (Engineering enzyme subsite specificity: preparation at 2.0ANG resolution of calf chymosin mutated at the Val111phe site, kinetic characterization, and x-ray analysis), Biochemistry, Vol 29, 1990, p 10, 9863-;

(iii) -supanene et al Site-specific mutations of calf chymosin B whichinflue milk-clotting activity (Site-specific mutation of calf chymosin B affecting the chymosin activity), Food Chemistry, Vol.62, 6.1998, p.133-;

zhang et al Functional indications of diagnostics bond, Cys45-Cys50, incomobinant prochymosin (Functional meaning of disulfide bonds (Cys45-Cys50) in recombinant chymozymogen), Biochimica et biophysica acta, Vol.1343, p.1997, p.12, p.278-.

None of the above prior art references directly and specifically describes/claims Any chymosin mutant/variant of (a).

Disclosure of Invention

The problem to be solved by the present invention is to provide chymosin variants with improved curd properties.

As discussed in the working examples herein-the present inventors have identified a number of improved camel (see example 6 herein) and bovine (see example 7 herein) chymosin variants.

Based on comparative analysis of camel and bovine variants-the present inventors have identified a number of other amino acid positions which are important in the context of chymosin variants which may be improved by making variants at one or more of these positions (see example 8 herein).

As known in the art-different native wild-type chymosin polypeptide sequences obtained from different mammalian species (e.g. such as, e.g., bovine, camel, ovine, porcine, or rat) have relatively high sequence similarity/identity.

In FIG. 1 herein, this is exemplified by the alignment of the different chymosin sequences referred to herein.

In view of this relatively close sequence relationship-it is believed that the 3D structures of the different native wild-type rennet enzymes are also relatively similar.

In the context of the present invention-naturally occurring wild-type chymosin (e.g. bovine chymosin or camel chymosin) may be an example of a parent polypeptide in the context of the present invention-i.e. a parent polypeptide which is altered to give a variant chymosin polypeptide of the present invention.

Without being limited by theory-it is believed that the chymosin-related amino acid positions described herein are of general importance in any of the related chymosins of interest herein (e.g., chymosins of, for example, cattle, camels, sheep, pigs, rats, etc.) -in the sense that an improved chymosin variant is generally obtainable by making a variant of one or more of these positions (e.g., an improved bovine, camel, sheep, pig or rat chymosin variant).

As described herein, the publicly known bovine chymosin B chymosin precursor sequence (Genbank accession number P00794-disclosed herein as SEQ ID NO:1) is used herein as a reference sequence to determine the amino acid position of a parent chymosin polypeptide of interest (e.g., camel, sheep, cow, etc.).

The bovine chymosin B chymosin precursor of SEQ ID NO:1 may alternatively be referred to herein as bovine (Bos bovis) chymosin B or just bovine chymosin. The sequence is also shown in figure 1 herein.

Another related chymosin sequence herein is the publicly known dromedarius chymosin sequence of SEQ ID NO:2 herein. Which may be alternatively referred to herein as camel chymosin. The sequence is also shown in figure 1 herein.

In the context of the present invention, it is believed that a parent chymosin polypeptide (e.g. a parent chymosin polypeptide from sheep or rat) having at least 65% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin) may be considered herein to have sufficient structural association with, for example, bovine or camel chymosin such that it may be improved by making a variant at any one of the amino acid positions as described herein.

Accordingly, a first aspect of the present invention relates to a method of preparing an isolated chymosin polypeptide variant comprising the steps of:

(a) the method comprises the following steps Making an alteration at one or more positions in a parent polypeptide having chymosin activity, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353; and

(b) the method comprises the following steps Preparing and isolating the altered polypeptide of step (a), thereby obtaining an isolated chymosin polypeptide variant, wherein the variant has chymosin activity;

and wherein:

(i) the method comprises the following steps The amino acid position of the parent polypeptide is determined by aligning the parent polypeptide with the polypeptide of SEQ ID No. 1 (bovine chymosin) — i.e. the polypeptide of SEQ ID No. 1 is used to determine the corresponding amino acid sequence in the parent polypeptide; and

(ii) the parent polypeptide has at least 65% sequence identity with the mature polypeptide of SEQ ID NO:1 (bovine chymosin) from amino acid position 59 to amino acid position 381 of SEQ ID NO: 1.

As is known in the art-the skilled person can routinely prepare and purify chymosin as well as chymosin variants based on his general knowledge.

In other words, once the skilled person has the relevant parent polypeptide of interest herein (e.g. from cow, camel, sheep, pig, or rat) with chymosin activity, it is routine work for the skilled person to make variants of the parent chymosin of interest.

A second aspect of the invention relates to an isolated chymosin polypeptide variant obtained with the method of the first aspect or any of its herein related embodiments.

The term "obtained" in relation to the above second aspect is to be understood as an isolated chymosin polypeptide variant that has been obtained using the method of the first aspect or any of its herein related embodiments.

Thus, the term "obtained" in relation to the second aspect should not be understood as obtainable.

As described herein-in the working examples herein, the polypeptide of SEQ ID NO:1 (bovine) is used as a parent polypeptide to prepare variants-which variants may be referred to herein as bovine chymosin variants.

Accordingly, a third aspect of the invention relates to an isolated chymosin polypeptide variant comprising:

(a) the method comprises the following steps An alteration at one or more positions in a parent polypeptide having chymosin activity, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353; and

(b) the method comprises the following steps Wherein the variant has chymosin activity;

and wherein:

(i) the method comprises the following steps The amino acid position of a parent polypeptide is determined by aligning the parent polypeptide with the polypeptide of SEQ ID No. 1 (bovine chymosin) — i.e. the polypeptide of SEQ ID No. 1 is used to determine the corresponding amino acid sequence in the parent polypeptide; and

(ii) the method comprises the following steps The parent polypeptide has at least 90% sequence identity to a mature polypeptide of SEQ ID NO. 1 (bovine chymosin) from amino acid position 59 to amino acid position 381 of SEQ ID NO. 1; and

(iii) the isolated variant polypeptide has less than 100% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin).

As described herein-in the working examples herein, a variant is prepared using a polypeptide of SEQ ID NO:2 (camelid chymosin) as a parent polypeptide-this variant may be referred to herein as a camelid chymosin variant.

Accordingly, a fourth aspect of the invention relates to an isolated chymosin polypeptide variant comprising:

(a) the method comprises the following steps An alteration at one or more positions in a parent polypeptide having chymosin activity, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353; and

(b) the method comprises the following steps Wherein the variant has chymosin activity;

and wherein:

(i) the method comprises the following steps The amino acid position of a parent polypeptide is determined by aligning the parent polypeptide with the polypeptide of SEQ ID No. 1 (bovine chymosin) — i.e. the polypeptide of SEQ ID No. 1 is used to determine the corresponding amino acid sequence in the parent polypeptide; and

(ii) the method comprises the following steps The parent polypeptide has at least 90% sequence identity to a mature polypeptide of SEQ ID NO. 2 (camelid chymosin) from amino acid position 59 to amino acid position 381 of SEQ ID NO. 2; and

(iii) the isolated variant polypeptide has less than 100% sequence identity to the mature polypeptide of SEQ ID NO:2 (camelid chymosin).

Isolated chymosin polypeptide variants as described herein may be used according to the art-e.g. for producing a food or feed product of interest (e.g. such as a milk-based product of interest, which may for example be a cheese product).

Thus, a fifth aspect of the invention relates to a method of producing a food or feed product comprising adding an effective amount of an isolated chymosin polypeptide variant as described herein to a food or feed ingredient and performing further processing steps to obtain the food or feed product.

Embodiments of the present invention are described below by way of examples only.

Defining:

all definitions of related terms herein are to be understood as such by a skilled artisan in view of the technical context herein relevant.

The term "chymosin" relates to enzymes of the EC 3.4.23.4 class. Chymosin has high specificity and it coagulates milk by cleaving a single 105-Ser-Phe- | Met-Ala-108 bond in the kappa-chain of casein. Another name used in the art is rennin.

The term "chymosin activity" relates to the chymosin activity of chymosin as understood by the skilled person in the context of the present invention.

The skilled person knows how to determine the herein relevant chymosin activity.

In working example 4 herein, an example of a standard method for determining specific activity of chymosin, otherwise known as coagulation activity or curd activity, is provided.

In working example 5 herein, an example of a standard method for determining proteolytic activity is provided.

As is known in the art-the so-called C/P ratio in this context is determined by the specific clotting activity (C) divided by the proteolytic activity (P).

As is known in the art-a higher C/P ratio generally means that the protein loss due to non-specific protein degradation during e.g. cheese production is reduced, i.e. the cheese yield is increased and the development of bitter taste in the cheese during ripening is reduced.

The term "isolated variant" means a variant that has been modified by man. In one aspect, the variant has at least 1% purity, e.g., at least 5% purity, at least 10% purity, at least 20% purity, at least 40% purity, at least 60% purity, at least 80% purity, and at least 90% purity, as determined using SDS PAGE.

The term "mature polypeptide" means the final form of the peptide after translation as well as any post-translational modifications (e.g., N-terminal processing, C-terminal truncation, glycosylation, phosphorylation, etc.). In the context of the present invention, a mature chymosin polypeptide of interest herein may be considered as an active chymosin polypeptide sequence-that is, a sequence without a precursor portion and/or a sequence of a protomer portion. A related example herein of a mature polypeptide is a mature polypeptide such as SEQ ID NO:1 (bovine chymosin) from amino acid position 59 to amino acid position 381 of SEQ ID NO: 1; or the mature polypeptide of SEQ ID NO:2 (camelid chymosin) from amino acid position 59 to amino acid position 381 of SEQ ID NO: 2.

The term "parent" or "parent polypeptide having chymosin activity" means a polypeptide that has been altered to make an enzyme variant of the invention. The parent may be a naturally occurring (wild-type) polypeptide or a variant thereof.

The term "sequence identity" relates to the relationship between two amino acid sequences or between two nucleotide sequences.

For The purposes of The present invention, The degree of sequence identity between two amino acid sequences is determined using The Needleman-Wunsch algorithm (Needleman and Wunsch,1970, J.Mol.biol.48: 443-. The optional parameters used are an open gap penalty of 10, a gap extension penalty of 0.5, and an EBLOSUM62 (EMBOSS version of BLOSUM 62) permutation matrix. The output of the Needle labeled "longest identity" (obtained using the-nobrief option) is used as the percent identity and is calculated as follows:

(same residue x 100)/(alignment Length-Total number of vacancies in alignment)

For The purposes of The present invention, The degree of sequence identity between two deoxynucleotide sequences is determined using The Needleman-Wunsch algorithm (Needleman and Wunsch,1970, as described above) as performed in The Needle program of The EMBOSS software package (EMBOSS: The European Molecular Biology open software Suite, Rice et al, 2000, as described above), preferably version 3.0.0 or later. The optional parameters used are an open gap penalty of 10, a gap extension penalty of 0.5, and the EDNAFULL (EMBOSS version of NCBI NUC 4.4) permutation matrix. The output of the Needle labeled "longest identity" (obtained using the-nobrief option) is used as the percent identity and is calculated as follows:

(identical deoxynucleotides x 100)/(alignment length-total number of gaps in alignment).

The term "variant" means a peptide having chymosin activity comprising alterations (i.e., substitutions, insertions, and/or deletions) at one or more (several) positions. Substitution means that the amino acid occupying one position is replaced by a different amino acid; deletion means the removal of an amino acid occupying one position; and insertion means addition of 1 to 3 amino acids adjacent to the amino acid occupying one position.

Amino acids can be natural or unnatural amino acids-for example, substitution by, for example, a particular D-isomer (or D-form), e.g., D-alanine, is theoretically possible.

The term "wild-type" chymosin peptide means chymosin expressed by a naturally occurring organism, such as a mammal (e.g., camel or cow) found in nature.

Drawings

FIG. 1 shows a schematic view of a: alignment of the different chymosin sequences referred to herein. The indicated "bovine chymosin B" is the bovine chymosin of SEQ ID NO:1 herein and the indicated "dromedary" is the camel chymosin of SEQ ID NO:2 herein. Using bovine chymosin of SEQ ID NO:1 as described herein as a reference sequence, it can for example be seen that bovine chymosin has a "V" in position 10 and camel chymosin has an "A" in the same position 10. It can also be seen, for example, that cattle/rats have a "Q" in position 352 and camel/llama have an "E" in the same position 352.

Sheep has 94.5% sequence identity to bovine SEQ ID NO:1 based on the chymosin sequence shown in FIG. 1; bactrian camel (C.bacttrianus) Has 83.2% sequence identity to bovine SEQ ID NO. 1; dromedary (camel chymosin of SEQ ID NO:2) has 84% sequence identity with bovine SEQ ID NO: 1; pig has 80.3% sequence identity with bovine SEQ ID NO. 1 and rat has 71.9% sequence identity with bovine SEQ ID NO. 1.

As understood by the skilled person in the context of the present invention-for example-the mature polypeptide sequence of sheep, bactrian camels, pig or rat chymosin is herein associated with a sequence identity percentage of the mature polypeptide of SEQ ID NO:1 (bovine chymosin-i.e., amino acid positions 59 to 381 of SEQ ID NO:1) that is quite similar to the above sequence identity percentages.

FIG. 2: the 3D structure of bovine chymosin, the 3D structure, is publicly available. An example is shown in which amino acid positions 296 and 294 are present in bovine chymosin.

Detailed Description

Determining the amino acid position of a chymosin of interest

As discussed above-the publicly known bovine chymosin sequence disclosed herein as SEQ ID NO:1 is used herein as a reference sequence to determine the amino acid position of a herein relevant chymosin polypeptide of interest (e.g., camel, sheep, cow, etc.).

For the purposes of the present invention, the polypeptide disclosed as SEQ ID NO 1 (bovine chymosin) is used for determining the corresponding amino acid residues in another chymosin polypeptide. The amino acid sequence of another chymosin polypeptide is aligned to the polypeptide disclosed in SEQ ID NO. 1 and based on the alignment, the amino acid position number corresponding to any amino acid residue in the polypeptide disclosed in SEQ ID NO. 1 is determined using the ClustalW algorithm described in working example 1 herein.

The identification of corresponding amino acid residues in another chymosin polypeptide may be confirmed by using The Needleman-Wunsch algorithm (Needleman and Wunsch,1970, J.Mol.biol.48:443-453) as performed in The Needle program of The EMBOSS software package, preferably version 3.0.0 or later (EMBOSS: The European Molecular Biology Open software suite, Rice et al 2000, Trends Genet.16: 276-277).

Based on the above well known computer programs-it is routine work for the skilled person to determine the amino acid position of a herein relevant chymosin polypeptide of interest (e.g. camel, sheep, cow, etc.).

An example of an alignment is shown in figure 1 herein.

As just one example-in FIG. 1, it can be seen, for example, that the bovine reference SEQ ID NO:1 as used herein has a "G" in position 50 and that the "unimodal camel" (SEQ ID NO:2 herein) has an "A" in this position 50.

Nomenclature of variants

In describing the variants of the invention, the nomenclature described below is employed for ease of reference. The accepted IUPAC single letter or three letter amino acid abbreviation is used.

The particular variations described in this "naming" section below may not be relevant variations in the context of the present invention-that is, this "naming" section is used only to describe nomenclature that is used in relation to it as such.

Replacement of. For amino acid substitutions, the following nomenclature is used: initial amino acid, position, substituted amino acid. Thus, the theoretical substitution of threonine by alanine at position 226 is denoted as "Thr 226 Ala" or "T226A". Multiple mutations are separated by a plus sign ("+"), e.g., "Gly 205Arg + Ser411 Phe" or "G205R + S411F", indicating the replacement of glycine (G) by arginine (R) and serine (S) by phenylalanine (F) at positions 205 and 411, respectively. For example, a substitution referred to as "226A" refers to a substitution of the parent amino acid at position 226 (e.g., T, Q, S or another parent amino acid) with alanine.

Absence of: for amino acid deletions, the following nomenclature is used: initial amino acid, position. Thus, the deletion of glycine at position 195 is denoted as "Gly 195" or "G195". Multiple deletions are separated by a plus sign ("+"), e.g., "Gly 195 + Ser 411" or "G195 + S411".

Insert into. For amino acid insertions, the following nomenclature is used: initial amino acid, position, initial amino acid, inserted amino acid. Thus, the insertion of a lysine after the glycine at position 195 is denoted as "Gly 195 GlyLys" or "G195 GK". The multiple amino acid insertions are denoted as [ initial amino acid, position, initial amino acid, inserted amino acid #1, inserted amino acid # 2; etc. of]. For example, the insertion of lysine and alanine after glycine at position 195 is denoted as "Gly 195 GlyLysAla" or "G195 GKA".

In these cases, the inserted amino acid residues are numbered by adding lower case letters to the position numbers of the amino acid residues preceding the inserted amino acid residue. In the above example, the sequence is thus:

parent strain:	variants:
		195	195 195a 195b
G	G-K-A

multiple changes. Variants comprising multiple alterations are separated by a plus sign ("+"), e.g., "Arg 170Tyr + Gly195 Glu" or "R170Y + G195E", representing the arginine and glycine at positions 170 and 195 of tyrosine and glutamic acid substitutions, respectively.

Different permutations.When different substitutions can be introduced at a position, the different substitutions are separated by a comma, e.g., "Arg 170Tyr, Glu" or "R170Y, E", indicating a substitution of arginine at position 170 with tyrosine or glutamic acid. Thus, "Tyr 167Gly, Ala + Arg170Gly, Ala" or "Y167G, a + R170G, a" represent the following variants:

"Tyr 167Gly + Arg170 Gly", "Tyr 167Gly + Arg170 Ala", "Tyr 167Ala + Arg170 Gly", and "Tyr 167Ala + Arg170 Ala".

Method for preparing separated chymosin polypeptide variant

As discussed above-as is known in the art, the skilled person can routinely prepare and purify chymosin and chymosin variants based on his general knowledge.

In other words, once the skilled person has a parent polypeptide of interest (e.g. from cow, camel, sheep, pig, or rat) with chymosin activity of interest, it is routine work for the skilled person to make a variant of the parent chymosin of interest.

An example of a suitable method for preparing and isolating chymosin (variant or parent) may be the well known e.g. fungal based recombinant expression/preparation techniques as described e.g. in WO02/36752a2(chr.

It is also routine for the skilled person to make alterations at one or more positions in a parent polypeptide having chymosin activity, wherein the alterations comprise substitutions, deletions or insertions of at least one amino acid position.

As known to the skilled person-this can be achieved, for example, by techniques based on so-called site-directed mutagenesis and recombinant expression/preparation.

It is also routine for the skilled person to determine whether a parent polypeptide relevant herein (e.g. camel or bovine wild-type chymosin) and/or a variant relevant herein has chymosin activity.

As is known in the art-chymosin activity may be determined by the so-called C/P ratio, which is determined by dividing the specific clotting activity (C) by the proteolytic activity (P).

As is known in the art-a higher C/P ratio generally means that the protein loss due to non-specific protein degradation during e.g. cheese production is reduced, i.e. the cheese yield is increased and the formation of bitter taste in the cheese during ripening is reduced.

In working example 4 herein, a suitable method for determining specific clotting activity (C) is described, and in working example 5 herein, a suitable method for determining proteolytic activity (P) is described.

Preferably, an isolated chymosin polypeptide variant as described herein is one wherein the variant has chymosin activity that yields a C/P ratio higher than the C/P ratio of a bovine chymosin comprising a mature polypeptide of SEQ ID NO:1 herein.

Preferably, an isolated chymosin polypeptide variant as described herein is one wherein the variant has chymosin activity resulting in a C/P ratio higher than the C/P ratio of a camel chymosin comprising a mature polypeptide of SEQ ID NO:2 herein.

More preferably, an isolated chymosin polypeptide variant as described herein is one wherein the variant has

-a chymosin activity yielding a C/P ratio higher than the C/P ratio of bovine chymosin comprising the mature polypeptide of SEQ ID NO:1 herein; and

chymosin activity yielding a C/P ratio higher than the C/P ratio of camel chymosin comprising a mature polypeptide of SEQ ID NO:2 as defined herein.

As discussed above, the publicly known bovine chymosin sequence disclosed herein as SEQ ID NO:1 is used herein as a reference sequence to determine the amino acid position of a herein relevant chymosin polypeptide of interest (e.g., camel, sheep, cow, etc.).

As discussed above-based on, for example, the computer sequence alignment programs discussed herein-it is routine for the skilled person to determine the herein relevant amino acid positions of the herein relevant chymosin polypeptides of interest (e.g. camel, sheep, cow, etc.).

For example, the term "parent polypeptide having at least 65% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin)" in the methods of the first aspect hereof may be taken as referring to the sequence-based restriction of the parent chymosin polypeptide used to prepare the relevant variants hereof.

In other words-a mature parent chymosin polypeptide (e.g. ovine or porcine) having at least 65% sequence identity to mature bovine chymosin is considered to be sufficiently identical to the structure of, for example, bovine or camel chymosin and thus relevant herein-that is, a mature parent chymosin polypeptide (e.g. from, for example, ovine or rat) which is considered to have at least 65% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin) may be considered herein to have sufficient structural association with, for example, bovine or camel chymosin in the context of the present invention and can therefore be improved by making variants at any amino acid position as described herein.

The camel chymosin polypeptide of SEQ ID NO:2 has 84% sequence identity to the bovine polypeptide of SEQ ID NO:1 (i.e. the complete SEQ ID NO:1 from positions 1 to 381, which comprises both precursor and pro sequence).

As the skilled person understands in the context of the present invention-a parent polypeptide of interest herein having chymosin activity may already be, for example, a variant of the corresponding wild-type chymosin.

For example, a camelid chymosin variant with, for example, 5-10 alterations (e.g. substitutions) compared to the wild type camelid chymosin polypeptide of SEQ ID NO:2 would still be a parent polypeptide with at least 65% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine) as required, for example, in the first aspect of the document.

In other words, an isolated chymosin polypeptide variant related herein may comprise alterations (e.g. substitutions) at positions other than, for example, the positions of the first aspect herein.

For the chymosin sequence shown in FIG. 1 herein-sheep has 94.5% sequence identity to bovine SEQ ID NO: 1; bactrian camels have 83.2% sequence identity to bovine SEQ ID NO 1; the pig has 80.3% sequence identity to bovine SEQ ID NO. 1; rat has 71.9% sequence identity to bovine SEQ ID NO 1.

As understood by the skilled person in the context of the present invention-for example-the percentage of sequence identity associated herein of mature sheep, Bactrian camel, pig or rat chymosin with the mature polypeptide of SEQ ID NO:1 (bovine chymosin-i.e., amino acid positions 59 to 381 of SEQ ID NO:1) is quite similar to the above-mentioned percentage of sequence identity.

Preferred variants are:

as discussed above-e.g., the first aspect relates to an isolated chymosin polypeptide variant wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353.

A preferred embodiment relates to an isolated chymosin polypeptide variant wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 134, 141, 143, 280, 281, 298, 300, 307, 309, 311, 352 and 353.

It may be preferred that at least one alteration is a substitution-that is, a related preferred embodiment herein relates to an isolated chymosin polypeptide variant wherein the alteration comprises a substitution of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353.

Preferably, an isolated chymosin polypeptide variant wherein the alteration comprises a substitution of at least one amino acid position corresponding to any one of positions 134, 141, 143, 280, 281, 298, 300, 307, 309, 311, 352 and 353.

Preferably, the permutation is wherein the permutation is 117N, 134Q, 141E, 143F, 156V, 241I, 279M, 280I, 281V, 298E, 300R, 307D, 309W, 311I, 325M, 350N, 352L, 352Q, 353L, or 353Q.

As understood by the skilled person in the context of the present invention, if a parent chymosin polypeptide already has, for example, a "V" at position 156, it cannot be understood that the substitution 156V was made for this particular parent chymosin polypeptide. As shown in figure 1 herein-rat wild-type chymosin has a "V" at position 156-substitution 156V may be considered irrelevant herein for the particular rat chymosin polypeptide sequence in figure 1.

Preferably, the permutation is wherein the permutation is 134Q, 141E, 143F, 280I, 281V, 298E, 300R, 307D, 309W, 311I, 352L, 352Q, 353L, or 353Q.

Preferably, the substitution is wherein the substitution is D117N, H134Q, Q141E, I143F, D156V, V241I, V279M, L280I, F281V, Q298E, Q300R, N307D, G309D, G309W, L311I, D325M, H350N, Q352L, E352L, E352Q, K353L or K353Q.

As understood by the skilled person in the context of the present invention, if a parent chymosin polypeptide does not have, e.g., a "D" at position 156, it cannot be understood that the substitution D156V was made for this particular parent chymosin polypeptide. As shown in figure 1 herein-rat wild-type chymosin has a "V" at position 156-the substitution D156V can thus be considered irrelevant herein for the particular rat chymosin polypeptide sequence in figure 1.

In a preferred embodiment, the substitution is wherein the substitution is H134Q, Q141E, I143F, L280I, F281V, Q298E, Q300R, N307D, G309D, G309W, L311I, Q352L, E352L, E352Q, K353L or K353Q.

In a preferred embodiment, the substitutions are wherein the substitution is:

F281V+V306I+I321L；

H134Q+I154L+D216S；

V261A+V263I+G309W+L311I+Y326F；

D156V+G309D+M314L+V317I；

H134Q+L280I+G309W；

R119Q+D156V+V375L；

Y79S+R119S+H204R；

Y79S+H134Q+Y365F+V375L；

Y194I+R213Q+G309D；

Y79S+D117N+I321L；

Y185F+D325M+E352Q；

Y79S+L224V+L311I；

S132F+H134Q+M200I+M215L+G221E；

F281V+G309W+S331Y+D337E；

D156V+G309D+M314L+V317I；

G128D+L188I+Y326F；

R119S+V241I+L280I+L311I+D325M；

R119Q+S284T+T297S+V306I+G309W

K279V+V281F；

Q298E+Q300R；

H350N+Q352E+K353L；

D307N + D309G; or

Q141E+I143F。

Preferred parent polypeptides having chymosin activity:

preferably, the parent polypeptide has at least 70% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin), more preferably, the parent polypeptide has at least 75% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin).

As but one example-A suitable related parent polypeptide herein may be, for example, bovine chymosin A-as is known in the art, bovine chymosin A may have only one amino acid difference compared to bovine chymosin B of SEQ ID NO:1 herein.

As discussed above, in the working examples herein, the polypeptide of SEQ ID NO:1 (bovine) is used as a parent polypeptide to make a variant, which may be referred to herein as a bovine chymosin variant.

Thus, in a preferred embodiment-the parent polypeptide has at least 90% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin), more preferably the parent polypeptide has at least 95% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin) and even more preferably the parent polypeptide has at least 97% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin). Preferably, the parent polypeptide may be the mature polypeptide of SEQ ID NO:1 (bovine chymosin).

As the skilled person understands in the context of the present invention-a parent polypeptide of interest herein having chymosin activity may already be, for example, a variant of the corresponding wild-type chymosin.

For example, a bovine chymosin variant with, for example, 5-10 alterations (e.g., substitutions) as compared to the mature wild-type bovine chymosin polypeptide of SEQ ID NO:1 would still be a parent polypeptide with at least 95% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin).

The mature polypeptide of SEQ ID NO:1 (bovine) is 323 amino acids in length-thus, a bovine chymosin variant with, for example, 25 amino acid substitutions would not be a parent polypeptide with at least 95% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin) compared to the mature wild type bovine chymosin polypeptide of SEQ ID NO: 1.

In other words and in general, an isolated chymosin polypeptide variant of interest herein may comprise alterations (e.g. substitutions) at positions other than, for example, the positions in the first aspect herein.

As discussed above-in the working examples herein, the polypeptide of SEQ ID NO:2 (camel) is used as a parent polypeptide to make variants-which variants may be referred to herein as camel chymosin variants.

Thus, in a preferred embodiment the parent polypeptide has at least 90% sequence identity to the mature polypeptide of SEQ ID NO:2 (camel chymosin), more preferably the parent polypeptide has at least 95% sequence identity to the mature polypeptide of SEQ ID NO:2 (camel chymosin) and even more preferably the parent polypeptide has at least 97% sequence identity to the mature polypeptide of SEQ ID NO:2 (camel chymosin). Preferably, the parent polypeptide may be the mature polypeptide of SEQ ID NO 2 (camel chymosin).

As the skilled person understands in the context of the present invention-a parent polypeptide having at least 90% sequence identity to the mature polypeptide of SEQ ID NO:2 (camel) is still within the scope of the sequence identity requirement in point (ii) of the first aspect hereof based on SEQ ID NO:1 (bovine) -that is, it will be a parent polypeptide having at least 65% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin).

Isolated variants of bovine chymosin:

as discussed above, in the working examples herein, the polypeptide of SEQ ID NO:1 (bovine) is used as a parent polypeptide to make a variant, which may be referred to herein as a bovine chymosin variant.

As discussed above-therefore, a third aspect relates to an isolated chymosin polypeptide variant comprising:

(a) the method comprises the following steps An alteration at one or more positions in a parent polypeptide having chymosin activity, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353; and

(b) the method comprises the following steps Wherein the variant has chymosin activity;

and wherein:

(i) the method comprises the following steps The amino acid position of the parent polypeptide is determined by aligning the parent polypeptide with the polypeptide of SEQ ID No. 1 (bovine chymosin) — i.e., the polypeptide of SEQ ID No. 1 is used to determine the corresponding amino acid sequence in the parent polypeptide; and

(ii) the method comprises the following steps The parent polypeptide has at least 90% sequence identity to a mature polypeptide of SEQ ID NO. 1 (bovine chymosin) from amino acid position 59 to amino acid position 381 of SEQ ID NO. 1; and

(iii) the method comprises the following steps The isolated variant polypeptide has less than 100% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin).

The above definitions and preferred embodiments also relate to this aspect.

Preferably, an isolated bovine chymosin polypeptide variant as described herein is one wherein the variant has chymosin activity resulting in a C/P ratio higher than the C/P ratio of a bovine chymosin comprising a mature polypeptide of SEQ ID NO: 1.

In a preferred embodiment-the parent polypeptide has at least 92% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin), more preferably the parent polypeptide has at least 95% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin) and even more preferably the parent polypeptide has at least 97% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin).

As understood by the skilled person in the context of the present invention, an isolated chymosin variant may comprise alterations (e.g. substitutions) in other amino acid positions than the amino acid positions given above.

For example, a bovine chymosin variant with, for example, 5-10 alterations (e.g., substitutions) will still be a parent polypeptide having at least 95% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin) compared to the wild-type bovine chymosin polypeptide of SEQ ID NO: 1.

It may be preferred that the isolated bovine chymosin variant comprises less than 30 amino acid changes (e.g. substitutions) compared to the mature polypeptide of SEQ ID NO:1 (bovine chymosin) or it may be preferred that the isolated bovine chymosin variant comprises less than 20 amino acid changes (e.g. substitutions) compared to the mature polypeptide of SEQ ID NO:1 (bovine chymosin) or it may be preferred that the isolated bovine chymosin variant comprises less than 10 amino acid changes (e.g. substitutions) compared to the mature polypeptide of SEQ ID NO:1 (bovine chymosin) or it may be preferred that the isolated bovine chymosin variant comprises less than 5 amino acid changes (e.g. substitutions) compared to the mature polypeptide of SEQ ID NO:1 (bovine chymosin).

As understood by the skilled person in the context of the present invention-the term "isolated variant polypeptide has less than 100% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin)" in point (iii) above relates to isolated bovine chymosin variants as described herein which of course should not have a polypeptide sequence which is 100% identical to the publicly known wild type bovine chymosin sequence of SEQ ID NO: 1.

A preferred embodiment relates to an isolated bovine chymosin polypeptide variant wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 134, 141, 143, 280, 281, 298, 300, 307, 309, 311, 352 and 353.

Preferably, the at least one alteration may be a substitution-that is, a related preferred embodiment herein relates to an isolated chymosin polypeptide variant wherein the alteration comprises a substitution of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353.

Preferably, an isolated chymosin polypeptide variant wherein the alteration comprises a substitution of at least one amino acid position corresponding to any one of positions 134, 141, 143, 280, 281, 298, 300, 307, 309, 311, 352 and 353.

Preferably, the permutation is wherein the permutation is 117N, 134Q, 141E, 143F, 156V, 241I, 279M, 280I, 281V, 298E, 300R, 307D, 309W, 311I, 325M, 350N, 352L, 352Q, 353L, or 353Q.

Preferably, the permutation is wherein the permutation is 134Q, 141E, 143F, 280I, 281V, 298E, 300R, 307D, 309W, 311I, 352L, 352Q, 353L, or 353Q.

Preferably, the substitution is wherein the substitution is D117N, H134Q, Q141E, I143F, D156V, V241I, V279M, L280I, F281V, Q298E, Q300R, N307D, G309D, G309W, L311I, D325M, H350N, Q352L, E352L, E352Q, K353L or K353Q.

In a preferred embodiment, the substitutions are wherein the substitution is:

F281V+V306I+I321L；

H134Q+I154L+D216S；

V261A+V263I+G309W+L311I+Y326F；

D156V+G309D+M314L+V317I；

H134Q+L280I+G309W；

R119Q+D156V+V375L；

Y79S+R119S+H204R；

Y79S+H134Q+Y365F+V375L；

Y194I+R213Q+G309D；

Y79S+D117N+I321L；

Y185F+D325M+E352Q；

Y79S+L224V+L311I；

S132F+H134Q+M200I+M215L+G221E；

F281V+G309W+S331Y+D337E；

D156V+G309D+M314L+V317I；

G128D+L188I+Y326F；

R119S+V241I+L280I+L311I+D325M；

R119Q+S284T+T297S+V306I+G309W

K279V+V281F；

Q298E+Q300R；

H350N+Q352E+K353L；

D307N + D309G; or

Q141E+I143F。

Isolated camel chymosin variants:

as discussed above-in the working examples herein, a polypeptide of SEQ ID NO:2 (camel chymosin) is used as a parent polypeptide to make a variant-which variant may be referred to herein as a camel chymosin variant.

As discussed above-therefore, the fourth aspect relates to an isolated chymosin polypeptide variant comprising:

(a) an alteration at one or more positions in a parent polypeptide having chymosin activity, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353; and

(b) the method comprises the following steps Wherein the variant has chymosin activity;

and wherein:

(i) the method comprises the following steps The amino acid position of the parent polypeptide is determined by aligning the parent polypeptide with the polypeptide of SEQ ID No. 1 (bovine chymosin) — i.e., the polypeptide of SEQ ID No. 1 is used to determine the corresponding amino acid sequence in the parent polypeptide; and

(ii) the method comprises the following steps The parent polypeptide has at least 90% sequence identity to the mature polypeptide of SEQ ID NO. 2 (camelid chymosin); and

(iii) the method comprises the following steps The isolated variant polypeptide has less than 100% sequence identity to the mature polypeptide of SEQ ID NO:2 (camelid chymosin).

The above definitions and preferred embodiments also relate to this aspect.

Preferably, an isolated camelid chymosin polypeptide variant as described herein is one wherein the variant has chymosin activity resulting in a higher C/P ratio than the C/P ratio of a camelid chymosin comprising a mature polypeptide of SEQ ID NO: 2.

In a preferred embodiment-the parent polypeptide has at least 92% sequence identity to the mature polypeptide of SEQ ID NO:2 (camel chymosin), more preferably the parent polypeptide has at least 95% sequence identity to the mature polypeptide of SEQ ID NO:2 (camel chymosin) and even more preferably the parent polypeptide has at least 97% sequence identity to the mature polypeptide of SEQ ID NO:2 (camel chymosin).

As understood by the skilled person in the context of the present invention, an isolated chymosin variant may comprise alterations (e.g. substitutions) in other amino acid positions than the amino acid positions given above.

For example, a camelid chymosin variant with, for example, 5-10 alterations (e.g., substitutions) compared to the wild type camelid chymosin polypeptide of SEQ ID NO:2 would still be a parent polypeptide with at least 95% sequence identity to the mature polypeptide of SEQ ID NO:2 (camelid chymosin).

Preferably, the isolated camel chymosin variant may comprise less than 30 amino acid alterations (e.g. substitutions) compared to the mature polypeptide of SEQ ID NO:2 (camel chymosin) or preferably the isolated camel chymosin variant may comprise less than 20 amino acid alterations (e.g. substitutions) compared to the mature polypeptide of SEQ ID NO:2 (camel chymosin) or preferably the isolated camel chymosin variant may comprise less than 10 amino acid alterations (e.g. substitutions) compared to the mature polypeptide of SEQ ID NO:2 (camel chymosin) or preferably the isolated camel chymosin variant may comprise less than 5 amino acid alterations (e.g. substitutions) compared to the mature polypeptide of SEQ ID NO:2 (camel chymosin).

As understood by the skilled person in the context of the present invention-the term "isolated variant polypeptide has less than 100% sequence identity to the mature polypeptide of SEQ ID NO:2 (camel chymosin)" in point (iii) above relates to isolated camel chymosin variants as described herein should of course not have a polypeptide sequence which is 100% identical to the publicly known wild type camel chymosin sequence of SEQ ID NO: 2.

A preferred embodiment relates to an isolated camelid chymosin polypeptide variant wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 134, 141, 143, 280, 281, 298, 300, 307, 309, 311, 352 and 353.

Preferably, the at least one alteration may be a substitution-that is, a related preferred embodiment herein relates to an isolated chymosin polypeptide variant wherein the alteration comprises a substitution of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353.

Preferably, an isolated chymosin polypeptide variant wherein the alteration comprises a substitution of at least one amino acid position corresponding to any one of positions 134, 141, 143, 280, 281, 298, 300, 307, 309, 311, 352 and 353.

Preferably, the permutation is wherein the permutation is 117N, 134Q, 141E, 143F, 156V, 241I, 279M, 280I, 281V, 298E, 300R, 307D, 309W, 311I, 325M, 350N, 352L, 352Q, 353L, or 353Q.

Preferably, the permutation is wherein the permutation is 134Q, 141E, 143F, 280I, 281V, 298E, 300R, 307D, 309W, 311I, 352L, 352Q, 353L, or 353Q.

Preferably, the substitution is wherein the substitution is D117N, H134Q, Q141E, I143F, D156V, V241I, V279M, L280I, F281V, Q298E, Q300R, N307D, G309D, G309W, L311I, D325M, H350N, Q352L, E352L, E352Q, K353L or K353Q.

In a preferred embodiment, the substitutions are wherein the substitution is:

F281V+V306I+I321L；

H134Q+I154L+D216S；

V261A+V263I+G309W+L311I+Y326F；

D156V+G309D+M314L+V317I；

H134Q+L280I+G309W；

R119Q+D156V+V375L；

Y79S+R119S+H204R；

Y79S+H134Q+Y365F+V375L；

Y194I+R213Q+G309D；

Y79S+D117N+I321L；

Y185F+D325M+E352Q；

Y79S+L224V+L311I；

S132F+H134Q+M200I+M215L+G221E；

F281V+G309W+S331Y+D337E；

D156V+G309D+M314L+V317I；

G128D+L188I+Y326F；

R119S+V241I+L280I+L311I+D325M；

R119Q+S284T+T297S+V306I+G309W

K279V+V281F；

Q298E+Q300R；

H350N+Q352E+K353L；

D307N + D309G; or

Q141E+I143F。

Method for making milk-based products

As discussed above-isolated chymosin polypeptide variants as described herein may be used according to the art-e.g. for making a milk-based product of interest (e.g. such as a cheese product).

As discussed above-one aspect of the present invention relates to a method of making a food or feed product comprising adding an effective amount of an isolated chymosin polypeptide variant as described herein to a food or feed ingredient and performing further processing steps to obtain a food or feed product.

Preferably, the food or feed product is a milk-based product and wherein the method comprises adding an effective amount of an isolated chymosin polypeptide variant as described herein to milk and performing further manufacturing steps to obtain the milk-based product.

The milk may be, for example, soy milk, sheep milk, goat milk, buffalo milk, yak milk, llama milk, camel milk or cow milk.

The milk-based product may for example be fermented milk, quark or cheese.

Aspects/embodiments herein-presented in claim form

The aspects and preferred embodiments described herein in the present invention can be presented/described in the form of so-called claims-see below.

1. A method of making an isolated chymosin polypeptide variant comprising the steps of:

(a) the method comprises the following steps Making an alteration at one or more positions in a parent polypeptide having chymosin activity, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353; and

(b) the method comprises the following steps Preparing and isolating the altered polypeptide of step (a), thereby obtaining an isolated chymosin polypeptide variant, wherein the variant has chymosin activity;

and wherein:

(i) the method comprises the following steps The amino acid position of the parent polypeptide is determined by aligning the parent polypeptide with the polypeptide of SEQ ID No. 1 (bovine chymosin) — i.e., the polypeptide of SEQ ID No. 1 is used to determine the corresponding amino acid sequence in the parent polypeptide; and

(ii) the method comprises the following steps The parent polypeptide has at least 65% sequence identity with the mature polypeptide of SEQ ID NO:1 (bovine chymosin) from amino acid position 59 to amino acid position 381 of SEQ ID NO: 1.

2. The method of making an isolated chymosin polypeptide variant of claim 1, wherein the isolated chymosin polypeptide variant has:

-a chymosin activity yielding a C/P ratio higher than the C/P ratio of bovine chymosin comprising the mature polypeptide of SEQ ID NO: 1; and

-a chymosin activity yielding a C/P ratio higher than the C/P ratio of a camelid chymosin comprising a mature polypeptide of SEQ ID NO: 2.

3. The method of making an isolated chymosin polypeptide variant of any of the preceding claims, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any of positions 134, 141, 143, 280, 281, 298, 300, 307, 309, 311, 352 and 353.

4. The method of making an isolated chymosin polypeptide variant of any preceding claim, wherein the alteration comprises a substitution of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353.

5. The method of making an isolated chymosin polypeptide variant of any of the preceding claims, wherein the alteration comprises a substitution of at least one amino acid position corresponding to any of positions 134, 141, 143, 280, 281, 298, 300, 307, 309, 311, 352 and 353.

6. The method of making an isolated chymosin polypeptide variant of claim 4, wherein the substitution is 117N, 134Q, 141E, 143F, 156V, 241I, 279M, 280I, 281V, 298E, 300R, 307D, 309W, 311I, 325M, 350N, 352L, 352Q, 353L or 353Q.

7. The method of making an isolated chymosin polypeptide variant of claim 6, wherein the substitution is 134Q, 141E, 143F, 280I, 281V, 298E, 300R, 307D, 309W, 311I, 352L, 352Q, 353L or 353Q.

8. The method of making an isolated chymosin polypeptide variant of claim 4, wherein the substitution is D117N, H134Q, Q141E, I143F, D156V, V241I, V279M, L280I, F281V, Q298E, Q300R, N307D, G309D, G309W, L311I, D325M, H350N, Q352L, E352L, E352Q, K353L or K353Q.

9. The method of making an isolated chymosin polypeptide variant of claim 8, wherein the substitution is H134Q, Q141E, I143F, L280I, F281V, Q298E, Q300R, N307D, G309D, G309W, L311I, Q352L, E352L, E352Q, K353L or K353Q.

10. The method of making an isolated chymosin polypeptide variant of claim 4, wherein the substitutions are:

F281V+V306I+I321L；

H134Q+I154L+D216S；

V261A+V263I+G309W+L311I+Y326F；

D156V+G309D+M314L+V317I；

H134Q+L280I+G309W；

R119Q+D156V+V375L；

Y79S+R119S+H204R；

Y79S+H134Q+Y365F+V375L；

Y194I+R213Q+G309D；

Y79S+D117N+I321L；

Y185F+D325M+E352Q；

Y79S+L224V+L311I；

S132F+H134Q+M200I+M215L+G221E；

F281V+G309W+S331Y+D337E；

D156V+G309D+M314L+V317I；

G128D+L188I+Y326F；

R119S+V241I+L280I+L311I+D325M；

R119Q+S284T+T297S+V306I+G309W

K279V+V281F；

Q298E+Q300R；

H350N+Q352E+K353L；

D307N + D309G; or

Q141E+I143F。

11. A method for making an isolated chymosin polypeptide variant as claimed in any preceding claim, wherein the parent polypeptide has at least 75% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin).

12. The method of making an isolated chymosin polypeptide variant of claim 11, wherein the parent polypeptide has at least 95% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin).

13. A method of making an isolated chymosin polypeptide variant as claimed in any of claims 1 to 10 wherein the parent polypeptide has at least 95% sequence identity with the mature polypeptide of SEQ ID No. 2 (camel chymosin) from amino acid position 59 to amino acid position 381 of SEQ ID No. 2.

14. An isolated chymosin polypeptide variant obtained by the method of any one of claims 1 to 13.

15. An isolated chymosin polypeptide variant comprising:

(a) the method comprises the following steps An alteration at one or more positions in a parent polypeptide having chymosin activity, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353; and

(b) the method comprises the following steps Wherein the variant has chymosin activity;

and wherein:

(i) the method comprises the following steps The amino acid position of the parent polypeptide is determined by aligning the parent polypeptide with the polypeptide of SEQ ID No. 1 (bovine chymosin) — i.e., the polypeptide of SEQ ID No. 1 is used to determine the corresponding amino acid sequence in the parent polypeptide; and

(ii) the method comprises the following steps The parent polypeptide has at least 90% sequence identity to a mature polypeptide of SEQ ID NO. 1 (bovine chymosin) from amino acid position 59 to amino acid position 381 of SEQ ID NO. 1; and

(iii) the method comprises the following steps The isolated variant polypeptide has less than 100% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin).

16. The isolated chymosin polypeptide variant of claim 15, wherein the isolated variant has chymosin activity that yields a higher C/P ratio than the C/P ratio of a bovine chymosin comprising a mature polypeptide of SEQ ID NO: 1.

17. The isolated chymosin polypeptide variant of any of claims 15 to 16, wherein the parent polypeptide has at least 97% sequence identity to the mature polypeptide of SEQ ID NO:1 (bovine chymosin).

18. The isolated chymosin polypeptide variant of any of claims 15 to 17, wherein the isolated bovine chymosin variant comprises less than 10 amino acid changes (e.g. substitutions) compared to the mature polypeptide of SEQ id no:1 (bovine chymosin).

19. The isolated chymosin polypeptide variant of any one of claims 15 to 18, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 134, 141, 143, 280, 281, 298, 300, 307, 309, 311, 352 and 353.

20. The isolated chymosin polypeptide variant of any one of claims 15 to 19, wherein the alteration comprises a substitution of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353.

21. The isolated chymosin polypeptide variant of claim 20, wherein the alteration comprises a substitution of at least one amino acid position corresponding to any one of positions 134, 141, 143, 280, 281, 298, 300, 307, 309, 311, 352 and 353.

22. The isolated chymosin polypeptide variant of claim 20, wherein the substitution is 117N, 134Q, 141E, 143F, 156V, 241I, 279M, 280I, 281V, 298E, 300R, 307D, 309W, 311I, 325M, 350N, 352L, 352Q, 353L, or 353Q.

23. The isolated chymosin polypeptide variant of claim 22, wherein the substitution is 134Q, 141E, 143F, 280I, 281V, 298E, 300R, 307D, 309W, 311I, 352L, 352Q, 353L or 353Q.

24. The isolated chymosin polypeptide variant of claim 22, wherein the substitution is D117N, H134Q, Q141E, I143F, D156V, V241I, V279M, L280I, F281V, Q298E, Q300R, N307D, G309D, G309W, L311I, D325M, H350N, Q352L, E352L, E352Q, K353L or K353Q.

25. The isolated chymosin polypeptide variant of claim 20, wherein the substitution is:

F281V+V306I+I321L；

H134Q+I154L+D216S；

V261A+V263I+G309W+L311I+Y326F；

D156V+G309D+M314L+V317I；

H134Q+L280I+G309W；

R119Q+D156V+V375L；

Y79S+R119S+H204R；

Y79S+H134Q+Y365F+V375L；

Y194I+R213Q+G309D；

Y79S+D117N+I321L；

Y185F+D325M+E352Q；

Y79S+L224V+L311I；

S132F+H134Q+M200I+M215L+G221E；

F281V+G309W+S331Y+D337E；

D156V+G309D+M314L+V317I；

G128D+L188I+Y326F；

R119S+V241I+L280I+L311I+D325M；

R119Q+S284T+T297S+V306I+G309W

K279V+V281F；

Q298E+Q300R；

H350N+Q352E+K353L；

D307N + D309G; or

Q141E+I143F。

26. An isolated chymosin polypeptide variant comprising:

(a) the method comprises the following steps An alteration at one or more positions in a parent polypeptide having chymosin activity, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353; and

(b) the method comprises the following steps Wherein the variant has chymosin activity;

and wherein:

(i) the method comprises the following steps The amino acid position of the parent polypeptide is determined by aligning the parent polypeptide with the polypeptide of SEQ ID No. 1 (bovine chymosin) — i.e., the polypeptide of SEQ ID No. 1 is used to determine the corresponding amino acid sequence in the parent polypeptide; and

(ii) the method comprises the following steps The parent polypeptide has at least 90% sequence identity to a mature polypeptide of SEQ ID NO. 2 (camelid chymosin) from amino acid position 59 to amino acid position 381 of SEQ ID NO. 2; and

(iii) the method comprises the following steps The isolated variant polypeptide has less than 100% sequence identity to the mature polypeptide of SEQ ID NO:2 (camelid chymosin).

27. An isolated chymosin polypeptide variant of claim 26, wherein the isolated variant has chymosin activity resulting in a higher C/P ratio than the C/P ratio of a camel chymosin comprising a mature polypeptide of SEQ ID NO:2 (camel chymosin).

28. An isolated chymosin polypeptide variant of any of claims 26 to 27, wherein the parent polypeptide has at least 97% sequence identity to the mature polypeptide of SEQ ID NO:2 (camel chymosin).

29. The isolated chymosin polypeptide variant of any of claims 26 to 28, wherein the isolated camel chymosin variant comprises less than 10 amino acid changes (e.g. substitutions) compared to the mature polypeptide of SEQ id No. 2 (camel chymosin).

30. The isolated chymosin polypeptide variant of any one of claims 26 to 29, wherein the alteration comprises a substitution, deletion or insertion of at least one amino acid position corresponding to any one of positions 134, 141, 143, 280, 281, 298, 300, 307, 309, 311, 352 and 353.

31. The isolated chymosin polypeptide variant of any one of claims 26 to 30, wherein the alteration comprises a substitution of at least one amino acid position corresponding to any one of positions 117, 134, 141, 143, 156, 241, 279, 280, 281, 298, 300, 307, 309, 311, 325, 350, 352 and 353.

32. The isolated chymosin polypeptide variant of claim 31, wherein the alteration comprises a substitution of at least one amino acid position corresponding to any one of positions 134, 141, 143, 280, 281, 298, 300, 307, 309, 311, 352 and 353.

33. The isolated chymosin polypeptide variant of claim 31, wherein the substitution is 117N, 134Q, 141E, 143F, 156V, 241I, 279M, 280I, 281V, 298E, 300R, 307D, 309W, 311I, 325M, 350N, 352L, 352Q, 353L, or 353Q.

34. The isolated chymosin polypeptide variant of claim 33, wherein the substitution is 134Q, 141E, 143F, 280I, 281V, 298E, 300R, 307D, 309W, 311I, 352L, 352Q, 353L or 353Q.

35. The isolated chymosin polypeptide variant of claim 33, wherein the substitution is D117N, H134Q, Q141E, I143F, D156V, V241I, V279M, L280I, F281V, Q298E, Q300R, N307D, G309D, G309W, L311I, D325M, H350N, Q352L, E352L, E352Q, K353L or K353Q.

36. The isolated chymosin polypeptide variant of claim 31, wherein the substitution is:

F281V+V306I+I321L；

H134Q+I154L+D216S；

V261A+V263I+G309W+L311I+Y326F；

D156V+G309D+M314L+V317I；

H134Q+L280I+G309W；

R119Q+D156V+V375L；

Y79S+R119S+H204R；

Y79S+H134Q+Y365F+V375L；

Y194I+R213Q+G309D；

Y79S+D117N+I321L；

Y185F+D325M+E352Q；

Y79S+L224V+L311I；

S132F+H134Q+M200I+M215L+G221E；

F281V+G309W+S331Y+D337E；

D156V+G309D+M314L+V317I；

G128D+L188I+Y326F；

R119S+V241I+L280I+L311I+D325M；

R119Q+S284T+T297S+V306I+G309W

K279V+V281F；

Q298E+Q300R；

H350N+Q352E+K353L；

D307N + D309G; or

Q141E+I143F。

37. A method of making a food or feed product comprising adding an effective amount of the isolated chymosin polypeptide variant of any of claims 14 to 36 to a food or feed ingredient and performing further processing steps to obtain a food or feed product.

38. A method of making a food or feed product according to claim 37, wherein the product is a milk-based product and wherein the method comprises adding an effective amount of the isolated chymosin polypeptide variant of any of claims 14 to 36 to milk and performing further processing steps to obtain a milk-based product.

39. The method of making a milk-based product of claim 38, wherein the milk is soy milk, sheep milk, goat milk, buffalo milk, yak milk, llama milk, camel milk, or cow milk.

40. A method of making a milk-based product according to any one of claims 38 to 39, wherein the milk-based product is a fermented dairy product, quark or cheese.