CN114309008B - Method for promoting conversion of food waste into reducing sugar - Google Patents

Abstract

The invention provides a method for promoting food waste to convert into reducing sugar, which comprises the following steps: crushing the food waste, extracting oil and pulping to obtain high-concentration food waste thick slurry; directly mixing choline chloride and glycerol without adding water to prepare a deep eutectic solvent; uniformly mixing the thick slurry of the food waste with a deep eutectic solvent, and performing ultrasonic centrifugation to collect solid-phase precipitate of the food waste; inoculating aspergillus into a container containing an enzyme production culture medium, extracting a crude enzyme solution after culture, and adding protease to obtain a mixed enzyme preparation; adding water into the solid phase precipitate to form a garbage homogeneous solution, and adding a mixed enzyme preparation to obtain a first mixture; placing the mixture in an enzymolysis tank, placing the mixture in a constant-temperature shaking table, oscillating to obtain a second mixture, and monitoring the concentration of fermentable sugar in the second mixture to regulate the enzyme amount. The invention can effectively shorten the reaction time and reduce the required temperature; the enzyme hydrolysis inhibition phenomenon caused by overhigh concentration of the product is reduced, the utilization rate of the enzyme is high, the cost is saved, and the reducing sugar can be quickly released from the biomass.

Description

A method for promoting the transformation of catering waste into reducing sugar

technical field

The invention belongs to the field of environmental engineering solid waste treatment, and in particular relates to a method for promoting the transformation of dining waste into reducing sugar.

Background technique

With the rapid development of my country's catering industry and the promotion and popularization of waste classification policies, my country's wet waste production has increased year by year. Among them, food waste is one of the main components of wet waste. In 2019, the national food waste production reached 120 million tons. Catering waste is an organic raw material with strong biotransformation potential, containing a large amount of sugar, protein and oil nutrients, which can be used to produce bioenergy such as biogas, organic fertilizer, volatile fatty acids (VFAs) and biomass fuel ethanol. Therefore, the recycling of catering waste has a great market prospect.

However, due to the large size of food waste particles and the organic matter wrapped in a solid phase, it is often difficult to be utilized by microorganisms, which limits the resource conversion efficiency of food waste. Catering waste contains a large amount of starch and cellulose that are not soluble and require a long time to decompose. The hydrolysis rate of such sugars restricts the fermentation start time. In the process of biotransformation, sugars are preferentially utilized by microorganisms compared to proteins and lipids. Among them, fermentable sugars are the most easily available organic substances for microorganisms in sugars, and can be biotransformed in a short time. Sugar concentration is one of the important means to enhance its biodegradability.

In order to convert macromolecular sugars (starch and cellulose, etc.) into small molecular fermentable sugars, it is often necessary to pretreat food waste to solubilize and hydrolyze organic matter in the waste. Cellulose and hemicellulose, which are abundant in food waste, are highly resistant to disintegration due to their stable structure, thus, proper pretreatment is required to deconstruct its interwoven components and disrupt the H-bond network of biomass , making polysaccharides easier to hydrolyze. Although ionic liquids are considered ideal pretreatment agents due to their special solvating properties, their high synthesis cost, toxicity, and biodegradability restrict their industrial use.

Deep eutectic solvents have very similar solvation properties to ionic liquids, and have many advantages, such as good biocompatibility with glucoamylase, easy preparation, and biodegradability, which make deep eutectic solvents the green color of ionic liquids. and sustainable alternatives have high prospects for use. Deep eutectic solvents can be separated after pretreatment and reused in subsequent pretreatment cycles. However, the relatively high viscosity of deep eutectic solvents may be a limiting factor that may hamper the speed of biomass pretreatment.

Enzymatic hydrolysis is also widely used to increase the concentration of fermentable sugar in various raw materials. It has the advantages of no need for additional equipment, energy saving, simple operation, and no by-products. It can hydrolyze a variety of macromolecules including cellulose Sugar substances can further increase the concentration of reducing sugar in the food waste slurry. The widely studied fermentable sugar substrates include commercial starch, crop straw, bamboo, etc. However, there are problems of high cost of raw materials and less utilization of raw materials from urban sources; in addition, enzyme reagents mainly use glucoamylase, cellulase and semi Cellulase has a single composition and high commercial enzyme price, which restricts the large-scale application of enzymatic hydrolysis. Urban catering waste is cheap and easy to obtain. However, it has complex components. At present, there is a lack of compound enzyme reagents for the characteristics of catering waste in my country.

Contents of the invention

Aiming at the above-mentioned problems in the prior art, the present invention provides a method for promoting the conversion of catering waste into reducing sugar. Aiming at the characteristics of high solid content and rich starch and cellulose substances in my country's catering waste, the present invention uses the mixed carbohydrase produced by Aspergillus niger and supplements additional protease, and strengthens the insolubility in catering waste by adding enzymes in batches. The hydrolysis of macromolecular sugars greatly increases the concentration of fermentable sugars in catering waste. At the same time, the real-time concentration of fermentable sugars is monitored by the control system to control the dosage of enzyme solution. It provides a feasible method for the high cost of the configuration of the compound enzyme and the high cost of enzymatic treatment.

Technical scheme of the present invention is as follows:

The invention provides specific steps for promoting the conversion of catering waste to form reducing sugar:

(1) Crushing catering waste, extracting oil and making pulp to obtain thick slurry of high-concentration catering waste;

(2) directly mixing choline chloride and glycerin without adding water, heating and stirring the resulting mixture until forming a uniform and transparent liquid, and preparing a deep eutectic solvent whose composition is choline chloride/glycerin;

(3) Cool the deep eutectic solvent obtained in step (2) to room temperature before use, mix the thick slurry of food waste obtained in step (1) with the deep eutectic solvent, and perform ultrasonic pretreatment on it. Cool it to room temperature, and after centrifugation, recover the mixed solution containing deep eutectic solvent for the next round of pretreatment, and collect the solid phase precipitation of food waste for subsequent enzymatic treatment;

(4) Inoculate Aspergillus into a container containing an enzyme-producing medium, extract its crude enzyme liquid after culturing; then add protease to obtain a mixed enzyme preparation;

(5) adding the solid-phase precipitate obtained in step (3) to water to form a garbage homogeneous liquid, adjusting the solid concentration TS, adjusting its pH, adding the mixed enzyme preparation obtained in step (4) to obtain the first mixture;

(6) Put the first mixture obtained in step (5) into the enzymatic hydrolysis tank and shake it in a constant temperature shaker to obtain the second mixture, monitor the concentration of fermentable sugar in the second mixture through the control system, and add it intermittently Supplement the mixed enzyme preparation and adjust the amount of enzyme through feedback.

Further, in the step (1), the particle size of the concentrated slurry of catering waste is less than 1mm; the oil content after oil extraction and pulping is less than 4%; and the concentration range of TS is 200-300g/L.

Further, the ratio of choline chloride to glycerol in the step (2) is 1 mol choline chloride and 3-12 mol glycerin, and the resulting mixture is heated at 50-70°C and stirred at 120-250rpm for 1h-3h until A homogeneous and transparent liquid is formed, and a deep eutectic solvent is prepared.

Further, in the step (3), the food waste thick slurry obtained in the step (1) is uniformly mixed with the deep eutectic solvent in a ratio of 1:1 to 5 by volume; the frequency of ultrasonic pretreatment is 15 to 30 kHz, The amplitude is 30-60%, the power is 30-50w, the pulse period is 20-30 seconds on/10 seconds off, and the processing time is 15-30 minutes.

Further, in the step (4), the Aspergillus is Aspergillus niger;

Further, the culture method is solid-state fermentation; the culture method is to add 10g to 20g of enzyme-producing medium into the Erlenmeyer flask, sterilize it in a sterilizing pot at 121°C for 20min, and then drop the temperature to 30°C Insert 1mL～3mL of Aspergillus niger spore suspension; wherein, the concentration of Aspergillus niger spore suspension is 0.8～1.2×10 ^-8 CFU/mL;

Further, the method for extracting the crude enzyme liquid is as follows: take 10 g of the bacterial liquid after 3-6 days of cultivation, add 40 to 60 mL of sodium acetate buffer solution with a pH of 4.5 to 4.7, put it in at a temperature of 38 to 45 ° C, and rotate Extract in a shaker at 150-180rpm for 1-2 hours, filter and centrifuge to obtain the crude enzyme solution;

Further, the formulation of the enzyme production medium is glucose 10g/L, MgSO ₄ ·7H ₂ O 1.0g/L, (NH ₄ ) ₂ SO ₄ 3.0g/L, KH ₂ PO ₄ 3.0g/L, NaH ₂ PO ₄ 2H ₂ O 1.69g/L, MnSO ₄ H ₂ O 0.04g/L, ZnCl ₂ 0.02g/L, CaCl ₂ 0.076g/L, CuSO ₄ 5H ₂ O 0.015g/L, CoCl ₂ 6H ₂ O 0.015g/L, FeSO ₄ 7H ₂ O 0.3g/L and EDTA-2Na 0.67g/L;

Further, the enzyme activity of the crude enzyme solution is 14,000-22,000 U/mL, and has a strong ability to hydrolyze macromolecular sugars, wherein 1 enzyme activity unit is defined as the amount of enzyme required to form 1 mg of reducing sugar within 1 hour;

Further, the protease activity is 350-700 LAPU/g, wherein 1 LAPU, i.e. leucine aminopeptidase unit, is the amount of enzyme needed to hydrolyze 1 millimole of L-leucine-p-nitroaniline per minute;

Further, the ratio of the mixed enzyme preparation is: crude enzyme liquid: protease 1g: 0.2-0.5g.

Further, in the step (5), the TS concentration ranges from 50 to 200 g/L, and the pH of the garbage homogeneous liquid is adjusted to 4.5 to 5.5.

Further, in the step (5), the addition ratio of the mixed enzyme preparation is: the added amount of the mixed enzyme preparation: the wet weight of the garbage homogeneous liquid is 1g: 100g-250g.

Further, in the step (6), the temperature of the constant temperature shaker is 45°C-55°C; the rotation speed is 120-200rpm, and the time is 6h-24h.

Further, in the step (6), the control system uses an automatic sampling method to regularly measure the fermentable sugar concentration of the second mixture every 15 to 60 minutes using a fully automatic reducing sugar analyzer connected to the enzymolysis tank;

Further, the method of intermittently adding the enzyme preparation is: detecting the total sugar concentration of the garbage homogeneous liquid, setting it as the upper limit T of reducible sugar, and detecting that the fermentable sugar concentration of the second mixture is less than 50% of the T value. %, the mixed enzyme preparation will be replenished automatically, and the replenishment amount will be 1/4 of the initial mixed enzyme preparation addition amount; when the fermentable sugar concentration is detected to be 50-70% of the T value, the supplement amount will be 1/4 of the initial mixed enzyme preparation addition amount /8; when the concentration of fermentable sugar is detected to be 70% to 90% of T value, the enzyme will not be supplemented until the next time the concentration is measured; Fermenting the catering garbage slurry with sugar concentration, re-dosing the first mixture described in the fresh step (5) in the enzymolysis tank, repeating the step (6), and performing multiple batches of enzymatic processes.

The beneficial technical effects of the present invention are:

Aiming at the characteristics of high solid content and rich starch and cellulose substances in the catering waste in our country, the present invention uses the combined pretreatment method of deep eutectic solvent and ultrasonic to degrade the cellulose in the catering waste, which can effectively shorten the reaction time and Reduce the temperature required for efficient pretreatment to achieve a more rapid release of sugars from the biomass. The method has the advantages of simple operation and remarkable effect of promoting conversion to form reducing sugar.

The preparation method of the deep eutectic solvent prepared by the present invention is simple, environmentally friendly, biodegradable, does not cause inhibition to subsequent enzymatic treatment, and has recyclability, and can be separated after pretreatment and repeated in subsequent pretreatment cycles use. Realize the repeated utilization of raw materials and reduce costs.

In order to reduce the cost of enzyme reagents, the present invention utilizes Aspergillus niger to produce crude enzymes with the ability to hydrolyze polysaccharides. In addition, some carbohydrates cannot be released due to the encapsulation of proteins, so additional proteases can further increase the concentration of fermentable sugars after enzymatic hydrolysis of food waste .

The present invention produces crude enzyme liquid through Aspergillus, which can greatly reduce the cost of enzymes. The crude enzyme liquid produced contains a large number of rich carbohydrases that can be used to hydrolyze cellulose and starch in food waste. Sugars are released to achieve the purpose of producing a large amount of reducing sugars. The method has the advantage of remarkable effect of promoting conversion to form reducing sugar.

The invention can effectively reduce the inhibition of enzyme hydrolysis caused by high product concentration by feeding batches, and automatically detecting the concentration of reducing sugar and automatically replenishing the mixed enzyme preparation. The enzyme utilization rate is high, and the addition of enzymes can be reduced at the same time volume, cost savings. The method has the advantages of simple operation and remarkable effect of promoting conversion to form reducing sugar.

Description of drawings

Fig. 1 is the specific steps of the method for promoting the conversion of catering waste to form reducing sugars.

Detailed ways

The present invention will be specifically described below in conjunction with the accompanying drawings and embodiments. Apparently, the described embodiments are only some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example 1:

(1) As shown in Figure 1, use a cooking machine to crush the catering waste to a particle size of less than 0.5mm, extract oil by cooking to an oil content of 1.8%, and add tap water to adjust its TS to 260g/L.

(2) Mix 1 mol of choline chloride with 6 mol of glycerol without adding water, heat the resulting mixture at 58°C and stir at 200 rpm for 2 hours until a uniform and transparent liquid is formed, and the prepared composition is choline chloride/glycerin deep eutectic solvent.

(3) Cool the prepared deep eutectic solvent to room temperature, uniformly mix the thick slurry of food waste obtained in step 1 with the deep eutectic solvent at a volume ratio of 1:3, and then perform ultrasonic treatment on it, and the frequency of ultrasonic pretreatment is 20kHz, the amplitude is 50%, the power is 38w, the pulse period is 25 seconds on/10 seconds off, and the processing time is 22 minutes. After it was cooled to room temperature, it was centrifuged, and the mixed solution containing deep eutectic solvent was recovered for the next round of pretreatment, and the solid-phase precipitation of food waste was collected for subsequent enzymatic treatment.

(4) Add 15g of enzyme-producing medium in a 250mL Erlenmeyer flask, and after sterilizing at 121°C and 20min in a sterilizer, insert 2mL of spore suspension after the temperature drops to 30°C; Aspergillus niger ( Aspergillus niger) was inoculated into the container containing the enzyme-producing medium for solid-state fermentation, and the concentration of the Aspergillus niger spore suspension was 1.0×10 ^-8 CFU/mL; 10 g of the bacterial liquid after 5 days of cultivation was taken, and 50 mL of sodium acetate buffer solution (pH 4 .6), placed in a shaker with a temperature of 40°C and a rotating speed of 160rpm for 1.5h, filtered and centrifuged to obtain a crude enzyme solution, the enzyme activity of the obtained crude enzyme solution was 20000U/mL, and one enzyme activity unit was defined as The amount of enzyme required to form 1 mg of reducing sugar in 1 h. Also prepare a protease with an activity of 500 LAPU/g, wherein 1 LAPU (leucine aminopeptidase unit) is the amount of enzyme needed to hydrolyze 1 mmol of L-leucine-p-nitroaniline per minute. Mix the crude enzyme solution prepared by Aspergillus niger and protease in a certain ratio to form a mixed enzyme preparation, and the ratio is crude enzyme solution: protease 1g: 0.40g.

(5) Add water to the solid phase precipitation obtained in step 3 to form a homogeneous liquid, adjust the solid concentration (TS) to 100g/L, adjust the pH of the garbage homogeneous liquid to 4.8, and then add the amount of enzyme preparation: the wet weight of catering waste is Add the mixed enzyme preparation prepared in step 3 at a ratio of 1g:180g to obtain the first mixture.

(6) Put the first mixture obtained in step 5 into a constant temperature shaker at 50° C. with a rotation speed of 150 rpm to obtain a second mixture. Sampling is carried out regularly through the control system, and the fermentable sugar concentration of the second mixture is regularly measured every 30 minutes by means of a fully automatic reducing sugar measuring instrument connected to the enzymatic hydrolysis tank. Measure the total sugar concentration in the garbage homogeneous liquid as 44.8g/L, set the target concentration of reducing sugar as 40g/L, supplement the mixed enzyme preparation by intermittent dosing, the specific operation is to detect when the fermentable sugar concentration is less than 20g/L When the concentration of fermentable sugar is 20g/L-28g/L, the supplementary amount is 1/4 of the initial added amount of the mixed enzyme preparation. /8; detection When the fermentable sugar concentration is 28g/L-36g/L, do not supplement the enzyme until the next time the concentration is measured.

When the fermentable sugar concentration exceeds 40g/L, the enzymatic process ends, and the food waste slurry containing high fermentable sugar concentration is discharged. The first round of enzymatic catalysis lasted 8 hours, and the concentration of reducing sugar in the catering waste after this round of enzymatic catalysis was determined to be 41.9g/L, while the concentration of reducing sugar in the original catering waste slurry under the same conditions was 8.1g/L. Its 517% achieved the goal of converting catering waste into reducing sugar. After the end of this round, re-dosing fresh first mixture, repeat step 4, for multiple batches of enzymatic process.

Example 2:

(1) As shown in Figure 1, use a cooking machine to crush the catering waste to a particle size of less than 0.5mm, extract the oil by cooking to an oil content of 4%, and add tap water to adjust its TS to 300g/L.

(2) Add 1mol choline chloride to 12mol glycerin and mix it without water, heat the resulting mixture at 70°C and stir at 120rpm for 1h until a uniform and transparent liquid is formed, the prepared composition is choline chloride/glycerin deep eutectic solvent.

(3) Cool the prepared deep eutectic solvent to room temperature, uniformly mix the thick slurry of food waste obtained in step 1 with the deep eutectic solvent at a volume ratio of 1:5, and then perform ultrasonic treatment on it, and the frequency of ultrasonic pretreatment is 30kHz, the amplitude is 30%, the power is 30w, the pulse period is 20 seconds on/10 seconds off, and the processing time is 15 minutes. After it was cooled to room temperature, it was centrifuged, and the mixed solution containing deep eutectic solvent was recovered for the next round of pretreatment, and the solid-phase precipitation of food waste was collected for subsequent enzymatic treatment.

(4) Add 20g of enzyme-producing medium in a 250mL Erlenmeyer flask, after sterilizing at 121°C and 20min in a sterilizer, insert 3mL of spore suspension after the temperature drops to 30°C; Aspergillus niger ( Aspergillus niger) was inoculated into a container containing an enzyme-producing medium for solid-state fermentation, and the concentration of the Aspergillus niger spore suspension was 1.0×10 ^-8 CFU/mL; 10 g of the bacterial liquid after 6 days of cultivation was added to 50 mL of sodium acetate buffer (pH 4 .6), put it into a shaker with a temperature of 40°C and a rotation speed of 160rpm for 1.5h, filter and centrifuge to obtain a crude enzyme liquid, and the enzyme activity of the obtained crude enzyme liquid is 20000U/mL, and one enzyme activity unit is defined as The amount of enzyme required to form 1 mg of reducing sugar in 1 h. Also prepare a protease with an activity of 500 LAPU/g, wherein 1 LAPU (leucine aminopeptidase unit) is the amount of enzyme needed to hydrolyze 1 mmol of L-leucine-p-nitroaniline per minute. Mix the crude enzyme solution prepared by Aspergillus niger and protease in a certain ratio to form a mixed enzyme preparation, and the ratio is crude enzyme solution: protease 1g: 0.50g.

(5) Add water to the solid phase precipitation obtained in step 3 to form a homogeneous liquid, adjust the solid concentration (TS) to 200g/L, adjust the pH of the garbage homogeneous liquid to 5.5, and then add the amount of enzyme preparation: the wet weight of catering waste is Add the mixed enzyme preparation prepared in step 3 at a ratio of 1g:250g to obtain the first mixture.

(6) Put the first mixture obtained in step 5 into a constant temperature shaker at 55° C. with a rotational speed of 120 rpm to obtain a second mixture. Sampling is carried out regularly through the control system, and the fermentable sugar concentration of the second mixture is regularly measured every 30 minutes by means of a fully automatic reducing sugar measuring instrument connected to the enzymatic hydrolysis tank. Measure the total sugar concentration in the garbage homogeneous liquid to be 84.7g/L, set the target concentration of reducing sugar to 80g/L, supplement the mixed enzyme preparation by intermittent dosing, the specific operation is to detect when the fermentable sugar concentration is less than 40g/L When the concentration of fermentable sugar is 40g/L-56g/L, the supplementary amount is 1/4 of the initial added amount of the mixed enzyme preparation; /8; detection When the concentration of fermentable sugar is 56g/L～72g/L, do not supplement the enzyme until the next time the concentration is measured.

When the fermentable sugar concentration exceeds 80g/L, the enzymatic process ends, and the food waste slurry containing high fermentable sugar concentration is discharged. The first round of enzymatic catalysis took 12 hours in total, and the concentration of reducing sugar in the food waste after this round of enzymatic catalysis was determined to be 80.6g/L, while the concentration of reducing sugar in the original food waste slurry under the same conditions was 19.4g/L. Its 415% achieved the goal of converting food waste into reducing sugar. After the end of this round, re-dosing fresh first mixture, repeat step 4, for multiple batches of enzymatic process.

Example 3:

(1) As shown in Figure 1, use a cooking machine to crush the catering waste to a particle size of less than 0.8mm, extract oil by cooking to an oil content of 2.5%, and add tap water to adjust its TS to 200g/L.

(2) Mix 1 mol of choline chloride with 3 mol of glycerol without adding water, heat the resulting mixture at 50°C and stir at 250rpm for 3 hours until a uniform and transparent liquid is formed, the prepared composition is choline chloride/glycerin deep eutectic solvent.

(3) Cool the prepared deep eutectic solvent to room temperature, uniformly mix the thick slurry of food waste obtained in step 1 with the deep eutectic solvent at a volume ratio of 1:1, and then perform ultrasonic treatment on it, and the frequency of ultrasonic pretreatment is 15kHz, the amplitude is 60%, the power is 50w, the pulse cycle is 30 seconds on/10 seconds off, and the processing time is 30 minutes. After it was cooled to room temperature, it was centrifuged, and the mixed solution containing deep eutectic solvent was recovered for the next round of pretreatment, and the solid-phase precipitation of food waste was collected for subsequent enzymatic treatment.

(4) Add 15g of enzyme-producing medium in a 250mL Erlenmeyer flask, and after sterilizing at 121°C and 20min in a sterilizing pot, insert 2mL of spore suspension after the temperature drops to 30°C; Aspergillus niger ( Aspergillus niger) was inoculated into a container containing enzyme-producing medium for solid-state fermentation, and the concentration of Aspergillus niger spore suspension was 1.0×10 ^-8 CFU/mL; 10 g of the bacterial liquid after 3 days of cultivation was added to 50 mL of sodium acetate buffer (pH 4 .6), put it into a shaker with a temperature of 40°C and a rotating speed of 160rpm for 1 hour, filter and centrifuge to obtain a crude enzyme liquid, and the enzyme activity of the obtained crude enzyme liquid is 20000U/mL, and one enzyme activity unit is defined as 1 hour The amount of enzyme required to form 1 mg of reducing sugars. Also prepare a protease with an activity of 500 LAPU/g, wherein 1 LAPU (leucine aminopeptidase unit) is the amount of enzyme needed to hydrolyze 1 mmol of L-leucine-p-nitroaniline per minute. Mix the crude enzyme solution prepared by Aspergillus niger and protease in a certain ratio to form a mixed enzyme preparation, and the ratio is crude enzyme solution: protease 1g: 0.20g.

(5) Add water to the solid phase precipitation obtained in step 3 to form a homogeneous liquid, adjust the solid concentration (TS) to 50g/L, adjust the pH of the garbage homogeneous liquid to 4.5, and then add the amount of enzyme preparation: the wet weight of catering waste is Add the mixed enzyme preparation prepared in step 3 at a ratio of 1g:100g to obtain the first mixture.

(6) Put the first mixture obtained in step 5 into a constant temperature shaker at 45° C. with a rotation speed of 200 rpm to obtain a second mixture. Sampling is carried out regularly through the control system, and the fermentable sugar concentration of the second mixture is regularly measured every 15 minutes by using a fully automatic reducing sugar measuring instrument connected to the enzymatic hydrolysis tank. Measure the total sugar concentration in the garbage homogeneous liquid as 23.5g/L, set the target concentration of reducing sugar as 20g/L, supplement the mixed enzyme preparation by intermittent dosing, the specific operation is to detect when the fermentable sugar concentration is less than 10g/L When the concentration of fermentable sugar is 10g/L-14g/L, the supplementary amount is 1/4 of the initial added amount of the mixed enzyme preparation. /8; detection When the fermentable sugar concentration is 14g/L～18g/L, do not supplement the enzyme until the next time the concentration is measured.

When the concentration of fermentable sugar exceeds 20g/L, the enzymatic process ends, and the catering waste slurry containing high fermentable sugar concentration is discharged. The first round of enzymatic catalysis lasted 6 hours, and the concentration of reducing sugar in the catering waste after this round of enzymatic catalysis was determined to be 20.2g/L, while the concentration of reducing sugar in the original catering waste slurry under the same conditions was 4.31g/L. Its 469% achieved the goal of converting food waste into reducing sugar. After the end of this round, re-dosing fresh first mixture, repeat step 4, for multiple batches of enzymatic process.

Wherein, the formula of the enzyme-producing medium adopted in said embodiment 1-3 is:

Glucose 10g/L, MgSO ₄ 7H ₂ O 1.0g/L, (NH ₄ ) ₂ SO ₄ 3.0g/L, KH ₂ PO ₄ 3.0g/L, NaH ₂ PO ₄ 2H ₂ O 1.69g/L, MnSO ₄ ·H ₂ O 0.04g/L, ZnCl ₂ 0.02g/L, CaCl ₂ 0.076g/L, CuSO ₄ ·5H ₂ O 0.015g/L, CoCl ₂ ·6H ₂ O 0.015g/L, FeSO ₄ · 7H ₂ O 0.3g/L and EDTA-2Na 0.67g/L.

Although the embodiment of the present invention has been disclosed as above, it is not limited to the use listed in the specification and implementation, it can be applied to various fields suitable for the present invention, for those familiar with the art, for this For those of ordinary skill in the art, without departing from the principle and spirit of the present invention, various changes, modifications, substitutions and variations can be made to these embodiments, so without departing from the general concept defined by the claims and the equivalent scope Below, the invention is not limited to the specific details.

Claims (10)

1. A method for promoting food waste to convert into reducing sugar is characterized by comprising the following steps:

(1) Crushing the food waste, extracting oil and pulping to obtain high-concentration food waste thick slurry;

(2) Directly mixing choline chloride and glycerol without adding water, heating and stirring the obtained mixture until uniform and transparent liquid is formed, and preparing a deep eutectic solvent with the components of choline chloride/glycerol;

(3) Cooling the deep eutectic solvent obtained in the step (2) to room temperature before use, uniformly mixing the thick slurry of the food waste obtained in the step (1) with the deep eutectic solvent, carrying out ultrasonic pretreatment on the mixture, cooling the mixture to room temperature after the pretreatment, recycling the mixed solution containing the deep eutectic solvent after centrifugation for the next round of pretreatment, and collecting solid-phase sediment of the food waste for subsequent enzymatic treatment;

(4) Inoculating aspergillus into a container containing an enzyme production culture medium, and extracting a crude enzyme solution after culture; adding protease to obtain mixed enzyme preparation;

(5) Adding water into the solid-phase precipitate obtained in the step (3) to form a garbage homogeneous liquid, adjusting the solid concentration TS, adjusting the pH value of the garbage homogeneous liquid, and adding the mixed enzyme preparation obtained in the step (4) to obtain a first mixture;

(6) Placing the first mixture obtained in the step (5) in an enzymolysis tank, placing the enzymolysis tank in a constant-temperature shaking table, oscillating to obtain a second mixture, monitoring the concentration of fermentable sugar in the second mixture through a control system, supplementing a mixed enzyme preparation in an intermittent feeding mode, and regulating the enzyme amount through feedback;

in the step (4), the Aspergillus is Aspergillus niger;

the culture mode is solid state fermentation; the culture method comprises the steps of adding 10 g-20 g of enzyme production culture medium into a triangular flask, sterilizing in a sterilization pot at 121 ℃ for 20min, cooling to 30 ℃, and inoculating 1 mL-3 mL of Aspergillus niger spore suspension; wherein, the concentration of the Aspergillus niger spore suspension is 0.8-1.2 multiplied by 10 ^-8 CFU/mL；

The method for extracting the crude enzyme solution comprises the steps of taking 10g of the bacterium solution after 3-6d of culture, adding 40-60 mL of sodium acetate buffer solution with the pH value of 4.5-4.7, putting the mixture into a shaking table with the temperature of 38-45 ℃ and the rotating speed of 150-180 rpm, leaching for 1-2 h, filtering and centrifuging to obtain the crude enzyme solution;

the formula of the enzyme production culture medium is 10g/L glucose and MgSO ₄ ·7H ₂ O 1.0g/L、(NH ₄ ) ₂ SO ₄ 3.0g/L、KH ₂ PO ₄ 3.0g/L、NaH ₂ PO ₄ ·2H ₂ O 1.69g/L、MnSO ₄ ·H ₂ O 0.04g/L、ZnCl ₂ 0.02g/L、CaCl ₂ 0.076g/L、CuSO ₄ ·5H ₂ O 0.015g/L、CoCl ₂ ·6H ₂ O 0.015g/L、FeSO ₄ ·7H ₂ O0.3g/L and EDTA-2Na 0.67g/L;

the activity of the crude enzyme liquid enzyme is 14000-22000U/mL, and the hydrolysis capability to macromolecular saccharides is strong;

the protease activity is 350-700 LAPU/g;

the proportion of the mixed enzyme preparation is as follows: the crude enzyme solution is 1g of protease and is 0.2-0.5 g.

2. The method of claim 1, wherein: the grain diameter of the Chinese food and beverage garbage concentrated slurry in the step (1) is less than 1mm; the oil content is lower than 4% after oil extraction and pulping; the TS concentration range is 200-300 g/L.

3. The method of claim 1, wherein: in the step (2), the choline chloride and the glycerol are added into 3-12 mol of glycerol according to the proportion of 1mol of choline chloride to 3-12 mol of glycerol, the obtained mixture is heated at 50-70 ℃ and stirred for 1-3 h at 120-250 rpm until uniform and transparent liquid is formed, and the deep eutectic solvent is prepared.

4. The method of claim 1, wherein: in the step (3), the thick slurry of the food waste obtained in the step (1) and the deep eutectic solvent are uniformly mixed according to the volume ratio of 1;

the frequency of ultrasonic pretreatment is 15-30 kHz, the amplitude is 30-60%, the power is 30-50 w, the pulse period is 20-30 seconds on/10 seconds off, and the treatment time is 15-30 min.

5. The method of claim 1, wherein: 1 enzyme activity unit is defined as the amount of enzyme required to form 1mg of reducing sugar in 1 hour;

1LAPU, leucine aminopeptidase units, is the amount of enzyme required to hydrolyze 1 millimole of L-leucine-p-nitroaniline per minute.

6. The method of claim 1, wherein: in the step (5), the concentration range of TS is 50-200 g/L, and the pH value of the garbage homogeneous liquid is adjusted to 4.5-5.5.

7. The method of claim 1, wherein: in the step (5), the adding proportion of the mixed enzyme preparation is as follows: the addition amount of the mixed enzyme preparation is 1g.

8. The method of claim 1, wherein: in the step (6), the temperature of the constant-temperature shaking table is 45-55 ℃; the rotating speed is 120-200 rpm, and the total reaction time is 6-24 h.

9. The method of claim 1, wherein: in the step (6), the control system adopts an automatic sampling mode, and a full-automatic reducing sugar determinator connected with the enzymolysis tank is used for periodically determining the fermentable sugar concentration of the second mixture every 15-60 min;

the mode of the intermittent feeding of the enzyme preparation is as follows: detecting the total sugar concentration of the garbage homogenized liquid, setting the total sugar concentration as an upper limit value T of reducible sugar, and automatically supplementing the mixed enzyme preparation when detecting that the concentration of the fermentable sugar of the second mixture is less than 50% of the value T, wherein the supplementing amount is 1/4 of the adding amount of the initial mixed enzyme preparation; when the concentration of the fermentable sugar is detected to be 50-70% of the T value, the supplement amount is 1/8 of the addition amount of the initial mixed enzyme preparation; when the concentration of the fermentable sugar is detected to be 70-90% of the T value, enzyme is not supplemented, and the concentration is determined for the next time; and (3) when the concentration of the fermentable sugar is detected to exceed 90 percent T, ending the enzymatic process, discharging the food waste slurry with high concentration of the fermentable sugar, adding fresh first mixture in the step (5) into the enzymolysis tank, repeating the step (6), and carrying out a plurality of enzymatic processes.

10. A high fermentable sugar concentration food waste slurry produced by the process of any one of claims 1 to 9.

Images