阅读说明：本技术 一种低成本连续化生产聚乳酸用单体及其制备方法 (Low-cost monomer for continuously producing polylactic acid and preparation method thereof ) 是由 余旺旺 惠嘎子 于 2021-08-23 设计创作，主要内容包括：本发明涉及一种低成本连续化生产聚乳酸用单体及其制备方法。所述低成本连续化生产聚乳酸用单体由单糖液、多肽蓝藻液、酵母膏、产乳酸菌、氢氧化钙清液和草酸组成,所述单糖液由甘蔗下脚料、水、半纤维素酶、纤维素酶、木质素过氧化物酶、淀粉酶、木聚糖酶、外切葡聚糖酶、内切葡聚糖酶和葡糖糖苷酶反应制得,所述多肽蓝藻液由蓝藻粉、蛋白质内肽酶、蛋白质外肽酶、水、淀粉酶、纤维素酶和脂肪酶反应制得。本发明提供的低成本连续化生产聚乳酸用单体具有优异的纯度高、成本低和附加值高。(The invention relates to a monomer for continuously producing polylactic acid with low cost and a preparation method thereof. The monomer for continuously producing the polylactic acid at low cost consists of monosaccharide liquid, polypeptide cyanobacteria liquid, yeast extract, lactic acid producing bacteria, calcium hydroxide clear liquid and oxalic acid, wherein the monosaccharide liquid is prepared by reacting sugarcane leftovers, water, hemicellulase, cellulase, lignin peroxidase, amylase, xylanase, exoglucanase, endoglucanase and glucosaccharase, and the polypeptide cyanobacteria liquid is prepared by reacting cyanobacteria powder, protein endopeptidase, protein exopeptidase, water, amylase, cellulase and lipase. The monomer for continuously producing the polylactic acid with low cost has excellent purity, low cost and high added value.)

1. A low-cost monomer for continuously producing polylactic acid is characterized by comprising monosaccharide liquid, polypeptide cyanobacteria liquid, yeast extract and lactic acid producing bacteria in a mass ratio of 100: 0.04-9: 0.06-5: 8-25; the monosaccharide liquid is prepared by reacting sugarcane leftovers, water, hemicellulase, cellulase, lignin peroxidase, amylase, xylanase, exoglucanase, endoglucanase and glucosaccharase in a mass ratio of 40: 83-120: 0.1-2: 0.2-3: 0.05-0.5: 0.06-0.8: 0.03-2: 0.05-1: 0.04-1: 0.06-2; the polypeptide cyanobacteria liquid is prepared by reacting cyanobacteria powder, protein endopeptidase, protein exopeptidase, water, amylase, cellulase and lipase, wherein the mass part ratio of the cyanobacteria powder to the polypeptide cyanobacteria liquid is 35: 0.01-1: 0.02-2: 82-120: 0.01-1: 0.05-2: 0.02-0.7.

2. The monomer for low-cost continuous production of polylactic acid according to claim 1, wherein the mass part ratio of the monosaccharide liquid to the polypeptide cyanobacteria liquid to the yeast extract to the lactic acid producing bacteria is 100:5.3:0.9: 15.

3. The method for preparing the monomer for continuously producing the polylactic acid at low cost according to any one of claims 1 to 2, which is characterized by comprising the following steps:

(1) adding the cyanobacteria powder and water into a hydrothermal reaction kettle, adjusting the pH value to be 6.5-8.5, maintaining the hydrothermal reaction temperature to be 180-260 ℃, carrying out hydrothermal treatment for 0.5-6 h, adding the product, protein endopeptidase, protein exopeptidase, amylase, cellulase and lipase into the reaction kettle, stirring at the speed of 180r/min, carrying out enzymolysis reaction for 4-12 h under the condition of maintaining the system reaction temperature to be 53-68 ℃, heating to 90 ℃, inactivating the enzyme for 30min, and concentrating to 50% of solid content to obtain polypeptide cyanobacteria liquid;

(2) mixing sugarcane leftovers and water, pulping, transferring the mixture into a hydrothermal reaction kettle, adjusting the pH value to be 6.3-8.8, maintaining the hydrothermal reaction temperature to be 260-350 ℃, carrying out hydrothermal treatment for 2-10 h, adding the product, hemicellulase, cellulase, lignin peroxidase, amylase, xylanase, exoglucanase, endoglucanase and glucosaccharase into the reaction kettle, stirring at 280r/min, maintaining the system reaction temperature to be 55-69 ℃, carrying out enzymolysis reaction for 5-20 h, heating to 90 ℃, inactivating enzyme for 30min, and concentrating to 50% of solid content to obtain monosaccharide liquid;

(3) adding monosaccharide liquid, polypeptide blue algae liquid and yeast extract into a reaction kettle, uniformly mixing, sterilizing for 30min at 120 ℃ and 0.08MPa, cooling the temperature of the reaction kettle to 45-60 ℃, stirring at the speed of 60r/min, adding lactic acid producing bacteria and 80 parts by mass of water into the reaction kettle, continuously reacting for 3-25 h under the condition of continuously introducing sterile air, starting to discharge materials to a three-phase horizontal centrifuge, returning solid residues of the 4000r/min three-phase horizontal centrifuge to the fermentation tank, centrifugally separating clear liquid by a 12000r/min tube bundle centrifuge, returning the solid residues to the fermentation tank, concentrating the clear liquid by a 300nm ceramic membrane component, returning the concentrated liquid to the fermentation tank, performing reverse osmosis treatment on the permeate liquid, returning the permeate to the fermentation tank, neutralizing the concentrated liquid by 25 ℃ saturated calcium hydroxide solution at 0-5 ℃ until the pH value is 6.0-6.5, concentrating the product at 90 ℃ through a 20nm ceramic membrane module, returning the permeate to a fermentation tank, washing the concentrated solution with hot water at 90 ℃, filtering, transferring the solid into a reaction kettle, adjusting the pH to 2-3 with oxalic acid, filtering the product at 80 ℃, washing, concentrating and purifying the liquid product with ethanol to obtain a low-cost monomer for continuously producing polylactic acid; and (3) reacting the solid residues after filtering at 80 ℃ for 0.5-6 h by using dilute sulfuric acid under the hydrothermal treatment condition of 140-180 ℃, centrifuging, filtering, washing, drying, and performing heat treatment at 500-750 ℃ to obtain the calcium sulfate whisker.

4. The method for preparing the monomer for continuously producing the polylactic acid at low cost according to any one of claims 1 and 3, wherein the cyanobacteria powder is dry powder without adding a flocculating agent and removing toxicity of algal toxins.

5. The method for preparing the monomer for the low-cost continuous production of the polylactic acid according to any one of claims 1 and 3, wherein the sugarcane leftovers comprise but are not limited to sugarcane tips.

6. The method for preparing a monomer for low-cost continuous production of polylactic acid according to any one of claims 1 and 3, wherein the lactic acid-producing bacteria is one of yeast, Escherichia coli and lactic acid bacteria.

7. The method for producing monomers for polylactic acid at low cost and continuously according to any of claims 1 and 3, wherein the mass concentration of oxalic acid is 85% (wt.%) and the mass concentration of dilute sulfuric acid is 60% (wt.%).

Technical Field

The invention relates to the field of degradable resource utilization, in particular to a monomer for continuously producing polylactic acid at low cost and a preparation method thereof.

Background

Lactic acid is a hydroxy acid which is most widely found in the natural world and is applied to the fields of food, medicine, feed, chemical industry and the like, and polylactic acid obtained by polymerizing lactic acid as a monomer is favored by a plurality of industries due to excellent physicochemical properties and environment-friendly degradability. At present, the preparation of the polylactic acid monomer mainly adopts a fermentation method, has complex process and high purification cost, belongs to intermittent production, and cannot achieve continuous production, so that the production cost is high, and most enterprises give up using the polylactic acid monomer due to high price. In order to solve the defects of high production cost, complex production process and incapability of continuous production in the lactic acid fermentation production process as soon as possible, research institutions and enterprise technicians in related industries of various countries jointly and deeply research related theories and practices so as to solve the defects of high production cost, complex production process and incapability of continuous production in the lactic acid fermentation production process as soon as possible.

Disclosure of Invention

The invention aims to provide a monomer for continuously producing polylactic acid at low cost, which is prepared from monosaccharide liquid, polypeptide cyanobacteria liquid, yeast extract, lactic acid producing bacteria, calcium hydroxide clear liquid and oxalic acid, and has the advantages of excellent purity, low cost and high added value.

Another object of the present invention is to provide a method for producing the monomer for continuous production of polylactic acid at low cost.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a low-cost monomer for continuously producing polylactic acid comprises monosaccharide liquid, polypeptide cyanobacteria liquid, yeast extract and lactic acid producing bacteria, wherein the mass portion ratio of the monosaccharide liquid to the polypeptide cyanobacteria liquid is 100: 0.04-9: 0.06-5: 8-25; the monosaccharide liquid is prepared by reacting sugarcane leftovers, water, hemicellulase, cellulase, lignin peroxidase, amylase, xylanase, exoglucanase, endoglucanase and glucosaccharase in a mass ratio of 40: 83-120: 0.1-2: 0.2-3: 0.05-0.5: 0.06-0.8: 0.03-2: 0.05-1: 0.04-1: 0.06-2; the polypeptide cyanobacteria liquid is prepared by reacting cyanobacteria powder, protein endopeptidase, protein exopeptidase, water, amylase, cellulase and lipase, wherein the mass part ratio of the cyanobacteria powder to the polypeptide cyanobacteria liquid is 35: 0.01-1: 0.02-2: 82-120: 0.01-1: 0.05-2: 0.02-0.7.

Preferably, the mass part ratio of the monosaccharide liquid to the polypeptide cyanobacteria liquid to the yeast extract to the lactic acid producing bacteria is 100:5.3:0.9: 15.

The preparation method of the monomer for continuously producing the polylactic acid with low cost comprises the following steps:

(1) adding the cyanobacteria powder and water into a hydrothermal reaction kettle, adjusting the pH value to be 6.5-8.5, maintaining the hydrothermal reaction temperature to be 180-260 ℃, carrying out hydrothermal treatment for 0.5-6 h, adding the product, protein endopeptidase, protein exopeptidase, amylase, cellulase and lipase into the reaction kettle, stirring at the speed of 180r/min, carrying out enzymolysis reaction for 4-12 h under the condition of maintaining the system reaction temperature to be 53-68 ℃, heating to 90 ℃, inactivating the enzyme for 30min, and concentrating to 50% of solid content to obtain polypeptide cyanobacteria liquid; the purpose of the hydrothermal treatment is to improve the specific surface of the slurry and reduce the molecular weight and the enzymolysis efficiency of the slurry;

(2) mixing sugarcane leftovers and water, pulping, transferring the mixture into a hydrothermal reaction kettle, adjusting the pH value to be 6.3-8.8, maintaining the hydrothermal reaction temperature to be 260-350 ℃, carrying out hydrothermal treatment for 2-10 h, adding the product, hemicellulase, cellulase, lignin peroxidase, amylase, xylanase, exoglucanase, endoglucanase and glucosaccharase into the reaction kettle, stirring at 280r/min, maintaining the system reaction temperature to be 55-69 ℃, carrying out enzymolysis reaction for 5-20 h, heating to 90 ℃, inactivating enzyme for 30min, and concentrating to 50% of solid content to obtain monosaccharide liquid; the purpose of the hydrothermal treatment is to improve the specific surface of the slurry and reduce the molecular weight and the enzymolysis efficiency of the slurry;

(3) adding monosaccharide liquid, polypeptide blue algae liquid and yeast extract into a reaction kettle, uniformly mixing, sterilizing for 30min at 120 ℃ and 0.08MPa, cooling the temperature of the reaction kettle to 45-60 ℃, stirring at the speed of 60r/min, adding lactic acid producing bacteria and 80 parts by mass of water into the reaction kettle, continuously reacting for 3-25 h under the condition of continuously introducing sterile air, starting to discharge materials to a three-phase horizontal centrifuge, returning solid residues of the 4000r/min three-phase horizontal centrifuge to the fermentation tank, centrifugally separating clear liquid by a 12000r/min tube bundle centrifuge, returning the solid residues to the fermentation tank, concentrating the clear liquid by a 300nm ceramic membrane component, returning the concentrated liquid to the fermentation tank, performing reverse osmosis treatment on the permeate liquid, returning the permeate to the fermentation tank, neutralizing the concentrated liquid by 25 ℃ saturated calcium hydroxide solution at 0-5 ℃ until the pH value is 6.0-6.5, concentrating the product at 90 ℃ through a 20nm ceramic membrane module, returning the permeate to a fermentation tank, washing the concentrated solution with hot water at 90 ℃, filtering, transferring the solid into a reaction kettle, adjusting the pH to 2-3 with oxalic acid, filtering the product at 80 ℃, washing, concentrating and purifying the liquid product with ethanol to obtain a low-cost monomer for continuously producing polylactic acid; reacting the solid residues filtered at 80 ℃ for 0.5-6 h by dilute sulfuric acid under the hydrothermal treatment condition of 140-180 ℃, centrifuging, filtering, washing, drying, and performing heat treatment at 500-750 ℃ to obtain calcium sulfate whiskers; the centrifugal and membrane components are used for guaranteeing the continuous production of the lactic acid.

The invention has the beneficial effects that:

1. the blue algae powder aqueous solution is treated by adopting a hydrothermal treatment technology, so that the denaturation, expansion and degradation of blue algae protein molecules can be realized under a high-temperature and high-pressure state, and the enzymolysis efficiency of a subsequent enzyme preparation on the protein is obviously improved;

2. the water solution of the sugarcane leftovers is treated by adopting a hydrothermal treatment technology, so that the swelling and degradation of fibers and sugar molecules can be realized under the high-temperature and high-pressure state, and the enzymolysis efficiency of subsequent enzyme preparations on the fibers and the sugar is obviously improved;

3. after lactic acid is fermented for a certain time, the fermentation efficiency is influenced when the content of lactic acid reaches a certain amount, the lactic acid monomer in the fermentation liquid can be separated to the maximum extent by adopting a mode of combining centrifugation and a membrane assembly, the lactic acid monomer in a fermentation system is controlled within a high-efficiency fermentation range, and meanwhile, the fermentation liquid containing the lactic acid is effectively purified and concentrated, because the acidification reagent adopts oxalic acid, the oxalic acid is easily decomposed by heating, the difficulty in purifying the lactic acid is obviously reduced, the efficiency of purifying and concentrating the lactic acid is improved, meanwhile, byproducts can co-produce calcium sulfate whiskers by a hydrothermal technology, and can be applied to toughening modification of polylactic acid, so that the problem of large brittleness of a polylactic acid material is solved;

4. the process adopts agricultural solid wastes as raw materials, and the raw materials belong to profitable raw materials, so that the project income can be increased, and the process has a wide application prospect.

Detailed Description

The following description of specific embodiments of the present invention is provided in connection with examples to facilitate a better understanding of the present invention. These examples are intended to illustrate the invention and are not intended to limit the scope of the invention. Experimental procedures without specific conditions noted in the examples below, generally according to conditions conventional in the art or as suggested by the manufacturer; the raw materials, reagents and the like used are, unless otherwise specified, those commercially available from the conventional markets and the like. Any insubstantial changes and substitutions made by those skilled in the art based on the present invention are intended to be covered by the claims.

Example 1

A low-cost monomer for continuously producing polylactic acid comprises the following steps:

(1) adding 35 parts of cyanobacteria powder and 100 parts of water into a hydrothermal reaction kettle, adjusting the pH value to 8.0, maintaining the hydrothermal reaction temperature at 190 ℃ for hydrothermal treatment for 3 hours, adding the product, 0.6 part of endopeptidase, 1.2 parts of exopeptidase, 0.3 part of amylase, 0.8 part of cellulase and 0.2 part of lipase into the reaction kettle, stirring at 180r/min, maintaining the system reaction temperature at 58 ℃ for enzymolysis reaction for 8 hours, heating to 90 ℃ for enzyme deactivation for 30 minutes, and concentrating to 50% of solid content to obtain polypeptide cyanobacteria liquid;

(2) mixing 40 parts of sugarcane leftovers and 100 parts of water, pulping, transferring to a hydrothermal reaction kettle, adjusting the pH value to 8.2, carrying out hydrothermal treatment for 7 hours at 300 ℃, adding a product, 1.1 part of hemicellulase, 2.3 parts of cellulase, 0.3 part of lignin peroxidase, 0.3 part of amylase, 0.6 part of xylanase, 0.8 part of exoglucanase, 0.6 part of endoglucanase and 1.3 parts of glucosaccharase into the reaction kettle, stirring at 280r/min, carrying out enzymolysis reaction for 10 hours at 60 ℃ of the reaction temperature of the system, heating to 90 ℃ to inactivate enzyme for 30 minutes, and concentrating to 50% of solid content to obtain monosaccharide liquid;

(3) adding 100 parts of monosaccharide liquid, 5.3 parts of polypeptide blue algae liquid and 0.9 part of yeast extract into a reaction kettle, uniformly mixing, sterilizing at 120 ℃ and 0.08MPa for 30min, cooling the reaction kettle to 53 ℃, stirring at the speed of 60r/min, adding 15 parts of lactic acid producing bacteria and 80 parts of water into the reaction kettle, continuously reacting for 9h under the condition of continuously introducing sterile air, starting to discharge materials to a three-phase horizontal centrifuge, returning solid residues of the 4000r/min three-phase horizontal centrifuge to a fermentation tank, centrifugally separating the clear liquid by a 12000r/min tube bundle centrifuge, returning the solid residues to the fermentation tank, concentrating the clear liquid by a 300nm ceramic membrane component, returning the concentrated liquid to the fermentation tank, performing reverse osmosis treatment on the permeate liquid, returning the permeate liquid to the fermentation tank, neutralizing the concentrated liquid to the pH value of 6.2 at-5 ℃ by a 25 ℃ saturated calcium hydroxide solution, concentrating the product at 90 ℃ by a 20nm ceramic membrane module, returning the permeate to a fermentation tank, washing the concentrated solution by hot water at 90 ℃, filtering, transferring the solid to a reaction kettle, adjusting the pH to 2.6 by oxalic acid, filtering the product at 80 ℃, washing, concentrating and purifying the liquid product by ethanol to obtain the monomer for continuously producing the polylactic acid at low cost; and (3) reacting the solid residues after filtering at 80 ℃ for 0.8h by using dilute sulfuric acid under the condition of hydrothermal treatment at 165 ℃, centrifugally filtering, washing, drying, and performing heat treatment at 600 ℃ to obtain the calcium sulfate whisker.

Example 2

A low-cost monomer for continuously producing polylactic acid comprises the following steps:

(1) adding 35 parts of cyanobacteria powder and 82 parts of water into a hydrothermal reaction kettle, adjusting the pH value to 6.5, maintaining the hydrothermal reaction temperature at 180 ℃ for hydrothermal treatment for 6 hours, adding the product, 0.01 part of endopeptidase, 0.02 part of exopeptidase, 0.01 part of amylase, 0.05 part of cellulase and 0.02 part of lipase into the reaction kettle, stirring at 180r/min, maintaining the system reaction temperature at 53 ℃ for enzymolysis reaction for 12 hours, heating to 90 ℃ for enzyme deactivation for 30 minutes, and concentrating to 50% of solid content to obtain polypeptide cyanobacteria liquid;

(2) mixing 40 parts of sugarcane leftovers and 83 parts of water, pulping, transferring to a hydrothermal reaction kettle, adjusting the pH value to 6.3, carrying out hydrothermal treatment for 10 hours at 260 ℃, adding a product, 0.1 part of hemicellulase, 0.2 part of cellulase, 0.05 part of lignin peroxidase, 0.06 part of amylase, 0.03 part of xylanase, 0.05 part of exoglucanase, 0.04 part of endoglucanase and 0.06 part of glucosaccharase into the reaction kettle, stirring at 280r/min, carrying out enzymolysis reaction for 20 hours at 55 ℃ of the reaction temperature of the system, heating to 90 ℃ to inactivate enzyme for 30 minutes, and concentrating to 50% of solid content to obtain monosaccharide liquid;

(3) adding 100 parts of monosaccharide liquid, 0.04 part of polypeptide blue algae liquid and 0.06 part of yeast extract into a reaction kettle, uniformly mixing, sterilizing at 120 ℃ and 0.08MPa for 30min, cooling the temperature of the reaction kettle to 45 ℃, stirring at the speed of 60r/min, adding 8 parts of lactic acid producing bacteria and 80 parts of water into the reaction kettle, continuously reacting for 3h under the condition of continuously introducing sterile air, starting to discharge materials to a three-phase horizontal centrifuge, returning solid residues to the fermentation tank through a 4000r/min three-phase horizontal centrifuge, centrifugally separating the clear liquid through a 12000r/min tube bundle centrifuge, returning the solid residues to the fermentation tank, concentrating the clear liquid through a 300nm ceramic membrane module, returning the concentrated liquid to the fermentation tank, performing reverse osmosis treatment on the permeate liquid, returning the permeate liquid to the fermentation tank, neutralizing the concentrated liquid to the pH value of 6.0 at-5 ℃ through a 25 ℃ saturated calcium hydroxide solution, concentrating the product at 90 ℃ by a 20nm ceramic membrane module, returning the permeate to a fermentation tank, washing the concentrated solution by hot water at 90 ℃, filtering, transferring the solid to a reaction kettle, adjusting the pH to 2 by oxalic acid, filtering the product at 80 ℃, washing, concentrating and purifying the liquid product by ethanol to obtain the monomer for continuously producing the polylactic acid at low cost; and (3) reacting the solid residues after filtering at 80 ℃ for 6h by dilute sulfuric acid under the hydrothermal treatment condition at 140 ℃, centrifugally filtering, washing, drying, and performing heat treatment at 500 ℃ to obtain the calcium sulfate whisker.

Example 3

A low-cost monomer for continuously producing polylactic acid comprises the following steps:

(1) adding 35 parts of cyanobacteria powder and 120 parts of water into a hydrothermal reaction kettle, adjusting the pH value to 8.5, maintaining the hydrothermal reaction temperature at 260 ℃ for hydrothermal treatment for 0.5h, adding the product, 1 part of endopeptidase, 2 parts of exopeptidase, 1 part of amylase, 2 parts of cellulase and 0.7 part of lipase into the reaction kettle, stirring at the speed of 180r/min, maintaining the system reaction temperature at 68 ℃ for enzymolysis reaction for 4h, heating to 90 ℃ for enzyme deactivation for 30min, and concentrating to 50% of solid content to obtain polypeptide cyanobacteria liquid;

(2) mixing 40 parts of sugarcane leftovers and 120 parts of water, pulping, transferring to a hydrothermal reaction kettle, adjusting the pH value to 8.8, carrying out hydrothermal treatment for 2 hours at 350 ℃, adding a product, 2 parts of hemicellulase, 3 parts of cellulase, 0.5 part of lignin peroxidase, 0.8 part of amylase, 2 parts of xylanase, 1 part of exoglucanase, 1 part of endoglucanase and 2 parts of glucosaccharase into the reaction kettle, stirring at 280r/min, carrying out enzymolysis reaction for 5 hours at 69 ℃, heating to 90 ℃, inactivating enzymes for 30 minutes, and concentrating to 50% of solid content to obtain monosaccharide liquid;

(3) adding 100 parts of monosaccharide liquid, 9 parts of polypeptide blue algae liquid and 5 parts of yeast extract into a reaction kettle, uniformly mixing, sterilizing at 120 ℃ and 0.08MPa for 30min, cooling the temperature of the reaction kettle to 60 ℃, stirring at the speed of 60r/min, adding 25 parts of lactic acid producing bacteria and 80 parts of water into the reaction kettle, continuously reacting for 25h under the condition of continuously introducing sterile air, starting to discharge materials to a three-phase horizontal centrifuge, returning solid residues of the 4000r/min three-phase horizontal centrifuge to the fermentation tank, centrifugally separating clear liquid by a 12000r/min tube bundle centrifuge, returning the solid residues to the fermentation tank, concentrating the clear liquid by a 300nm ceramic membrane component, returning the concentrated liquid to the fermentation tank, performing reverse osmosis treatment on the permeate liquid, returning the permeate liquid to the fermentation tank, neutralizing the concentrated liquid by 25 ℃ saturated calcium hydroxide solution at 0 ℃ to pH 6.5, concentrating the product at 90 ℃ by a 20nm ceramic membrane module, returning the permeate to a fermentation tank, washing the concentrated solution by hot water at 90 ℃, filtering, transferring the solid to a reaction kettle, adjusting the pH to 3 by oxalic acid, filtering the product at 80 ℃, washing, concentrating and purifying the liquid product by ethanol to obtain the monomer for continuously producing the polylactic acid at low cost; and (3) reacting the solid residues after filtering at 80 ℃ for 0.5h by dilute sulfuric acid under the condition of hydrothermal treatment at 180 ℃, centrifuging, filtering, washing, drying, and carrying out heat treatment at 750 ℃ to obtain the calcium sulfate whisker.

Example 4

A low-cost monomer for continuously producing polylactic acid comprises the following steps:

(1) adding 35 parts of cyanobacteria powder and 89 parts of water into a hydrothermal reaction kettle, adjusting the pH value to 6.8, maintaining the hydrothermal reaction temperature at 195 ℃ for hydrothermal treatment for 2 hours, adding the product, 0.3 part of endopeptidase, 0.6 part of exopeptidase, 0.6 part of amylase, 0.3 part of cellulase and 0.2 part of lipase into the reaction kettle, stirring at 180r/min, maintaining the system reaction temperature at 55 ℃ for enzymolysis reaction for 6 hours, heating to 90 ℃ for enzyme deactivation for 30 minutes, and concentrating to 50% of solid content to obtain polypeptide cyanobacteria liquid;

(2) mixing 40 parts of sugarcane leftovers and 89 parts of water, pulping, transferring to a hydrothermal reaction kettle, adjusting the pH value to 6.5, maintaining the hydrothermal reaction temperature at 280 ℃ for hydrothermal treatment for 4 hours, adding a product, 0.3 part of hemicellulase, 1 part of cellulase, 0.2 part of lignin peroxidase, 0.3 part of amylase, 0.6 part of xylanase, 0.3 part of exoglucanase, 0.4 part of endoglucanase and 0.9 part of glucosaccharase into the reaction kettle, stirring at 280r/min, maintaining the system reaction temperature at 59 ℃ for enzymolysis reaction for 7 hours, heating to 90 ℃ for enzyme deactivation for 30 minutes, concentrating to 50% of solid content to obtain monosaccharide liquid;

(3) adding 100 parts of monosaccharide liquid, 3 parts of polypeptide blue algae liquid and 3 parts of yeast extract into a reaction kettle, uniformly mixing, sterilizing at 120 ℃ and 0.08MPa for 30min, cooling the temperature of the reaction kettle to 51 ℃, stirring at the speed of 60r/min, adding 12 parts of lactic acid producing bacteria and 80 parts of water into the reaction kettle, continuously reacting for 6h under the condition of continuously introducing sterile air, starting to discharge materials to a three-phase horizontal centrifuge, returning solid residues of the 4000r/min three-phase horizontal centrifuge to the fermentation tank, centrifugally separating clear liquid by a 12000r/min tube bundle type centrifuge, returning the solid residues to the fermentation tank, concentrating the clear liquid by a 300nm ceramic membrane component, returning the concentrated liquid to the fermentation tank, performing reverse osmosis treatment on the permeate, returning the permeate to the fermentation tank, neutralizing the concentrate by 25 ℃ saturated calcium hydroxide solution at-3 ℃ until the pH is 6.1, concentrating the product at 90 ℃ by a 20nm ceramic membrane module, returning the permeate to a fermentation tank, washing the concentrated solution by hot water at 90 ℃, filtering, transferring the solid to a reaction kettle, adjusting the pH to 2.3 by oxalic acid, filtering the product at 80 ℃, washing, concentrating and purifying the liquid product by ethanol to obtain the monomer for continuously producing the polylactic acid at low cost; and (3) reacting the solid residues after filtering at 80 ℃ for 2h by using dilute sulfuric acid under the condition of hydrothermal treatment at 150 ℃, centrifugally filtering, washing, drying, and carrying out thermal treatment at 590 ℃ to obtain the calcium sulfate whisker.

Example 5

A low-cost monomer for continuously producing polylactic acid comprises the following steps:

(1) adding 35 parts of cyanobacteria powder and 110 parts of water into a hydrothermal reaction kettle, adjusting the pH value to 7, maintaining the hydrothermal reaction temperature at 200 ℃ for hydrothermal treatment for 3 hours, adding the product, 0.5 part of endopeptidase, 1 part of exopeptidase, 0.5 part of amylase, 1 part of cellulase and 0.4 part of lipase into the reaction kettle, stirring at 180r/min, maintaining the system reaction temperature at 60 ℃ for enzymolysis reaction for 8 hours, heating to 90 ℃ for enzyme deactivation for 30 minutes, and concentrating to 50% of solid content to obtain polypeptide cyanobacteria liquid;

(2) mixing 40 parts of sugarcane leftovers and 100 parts of water, pulping, transferring to a hydrothermal reaction kettle, adjusting the pH value to 6.9, carrying out hydrothermal treatment for 6 hours at 300 ℃, adding a product, 1 part of hemicellulase, 1.5 parts of cellulase, 0.3 part of lignin peroxidase, 0.5 part of amylase, 1 part of xylanase, 0.5 part of exoglucanase, 0.6 part of endoglucanase and 1 part of glucosaccharase into the reaction kettle, stirring at 280r/min, carrying out enzymolysis reaction for 10 hours at 60 ℃ of the reaction temperature of a system, heating to 90 ℃ to inactivate enzyme for 30 minutes, and concentrating to 50% of solid content to obtain monosaccharide liquid;

(3) adding 100 parts of monosaccharide liquid, 5 parts of polypeptide blue algae liquid and 3 parts of yeast extract into a reaction kettle, uniformly mixing, sterilizing at 120 ℃ and 0.08MPa for 30min, cooling the temperature of the reaction kettle to 50 ℃, stirring at the speed of 60r/min, adding 15 parts of lactic acid producing bacteria and 80 parts of water into the reaction kettle, continuously reacting for 8h under the condition of continuously introducing sterile air, starting to discharge materials to a three-phase horizontal centrifuge, returning solid residues of the 4000r/min three-phase horizontal centrifuge to the fermentation tank, centrifugally separating clear liquid by a 12000r/min tube bundle type centrifuge, returning the solid residues to the fermentation tank, concentrating the clear liquid by a 300nm ceramic membrane component, returning the concentrated liquid to the fermentation tank, performing reverse osmosis treatment on the permeate, returning the permeate to the fermentation tank, neutralizing the concentrate by 25 ℃ saturated calcium hydroxide solution at-2 ℃ until the pH is 6.3, concentrating the product at 90 ℃ by a 20nm ceramic membrane module, returning the permeate to a fermentation tank, washing the concentrated solution by hot water at 90 ℃, filtering, transferring the solid to a reaction kettle, adjusting the pH to 2.6 by oxalic acid, filtering the product at 80 ℃, washing, concentrating and purifying the liquid product by ethanol to obtain the monomer for continuously producing the polylactic acid at low cost; and (3) reacting the solid residues filtered at 80 ℃ for 1h by dilute sulfuric acid under the hydrothermal treatment condition of 160 ℃, centrifugally filtering, washing, drying, and carrying out heat treatment at 680 ℃ to obtain the calcium sulfate whisker.

Example 6

A low-cost monomer for continuously producing polylactic acid comprises the following steps:

(1) adding 35 parts of cyanobacteria powder and 118 parts of water into a hydrothermal reaction kettle, adjusting the pH value to 8.2, maintaining the hydrothermal reaction temperature at 235 ℃ for hydrothermal treatment for 5 hours, adding a product, 0.7 part of endopeptidase, 1.3 parts of exopeptidase, 0.9 part of amylase, 1.7 parts of cellulase and 0.6 part of lipase into the reaction kettle, stirring at 180r/min, maintaining the system reaction temperature at 66 ℃ for enzymolysis reaction for 11 hours, heating to 90 ℃ for enzyme deactivation for 30 minutes, and concentrating to 50% of solid content to obtain polypeptide cyanobacteria liquid;

(2) mixing 40 parts of sugarcane leftovers and 108 parts of water, pulping, transferring to a hydrothermal reaction kettle, adjusting the pH value to 8.3, maintaining the hydrothermal reaction temperature at 310 ℃ for hydrothermal treatment for 8 hours, adding a product, 1.7 parts of hemicellulase, 2.3 parts of cellulase, 0.4 part of lignin peroxidase, 0.6 part of amylase, 1.6 parts of xylanase, 0.5 part of exoglucanase, 0.6 part of endoglucanase and 1.4 parts of glucosaccharase into the reaction kettle, stirring at 280r/min, maintaining the system reaction temperature at 63 ℃ for enzymolysis reaction for 15 hours, heating to 90 ℃ to inactivate enzyme for 30 minutes, and concentrating to 50% of solid content to obtain monosaccharide liquid;

(3) adding 100 parts of monosaccharide liquid, 6 parts of polypeptide blue algae liquid and 3 parts of yeast extract into a reaction kettle, uniformly mixing, sterilizing at 120 ℃ and 0.08MPa for 30min, cooling the temperature of the reaction kettle to 55 ℃, stirring at the speed of 60r/min, adding 21 parts of lactic acid producing bacteria and 80 parts of water into the reaction kettle, continuously reacting for 18h under the condition of continuously introducing sterile air, starting to discharge materials to a three-phase horizontal centrifuge, returning solid residues of the 4000r/min three-phase horizontal centrifuge to the fermentation tank, centrifugally separating clear liquid by a 12000r/min tube bundle centrifuge, returning the solid residues to the fermentation tank, concentrating the clear liquid by a 300nm ceramic membrane component, returning the concentrated liquid to the fermentation tank, performing reverse osmosis treatment on the permeate, returning the permeate to the fermentation tank, neutralizing the concentrated liquid by 25 ℃ saturated calcium hydroxide solution at-4 ℃ until the pH value is 6.4, concentrating the product at 90 ℃ by a 20nm ceramic membrane module, returning the permeate to a fermentation tank, washing the concentrated solution by hot water at 90 ℃, filtering, transferring the solid to a reaction kettle, adjusting the pH to 2.7 by oxalic acid, filtering the product at 80 ℃, washing, concentrating and purifying the liquid product by ethanol to obtain the monomer for continuously producing the polylactic acid at low cost; and (3) reacting the solid residues after filtering at 80 ℃ for 5 hours by using dilute sulfuric acid under the condition of hydrothermal treatment at 170 ℃, centrifugally filtering, washing, drying, and performing heat treatment at 700 ℃ to obtain the calcium sulfate whisker.

The chemical purity test results of the lactic acid of the low-cost monomer for continuously producing polylactic acid prepared in examples 1 to 6 and comparative examples 1 to 6 are shown in Table 1 below.

TABLE 1 Performance parameters of the low-cost monomers for continuous production of polylactic acid prepared in examples 1 to 6

As can be seen from Table 1, the monomer for continuously producing polylactic acid at low cost prepared in the embodiments of the present invention has excellent chemical purity, which indicates that the monomer for continuously producing polylactic acid at low cost prepared from the raw materials provided by the present invention has good chemical purity.

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.