Different Pretreatment Promoted Food Waste Hydrolysis And Lactic Acid Accumulation By Anaerobic Fermentation

Lactic acid is an important industrial product.Because of its many properties,lactic acid can be used as precursor or macromolecule compound?acrylic polymer?of small molecule?propylene glycol?.It is widely used in cosmetics,medicine,food,animal feed industry.Moreover,polylactide can be degraded by microorganisms,which is a common material in the packaging industry.It has huge economic value and environmental value.In order to meet market demand and pursue economic benefits,we need intensive fermentation technology,so as to achieve low cost and high efficiency.This is one of the two major problems in the production of industrial lactic acid.The main goal of this experiment is to establish a efficient lactic acid fermentation mode.The main results are as follows:?1?In this paper,Lactobacillus acidophilus was used as the main fermentation agent to test the biochemical properties of the bacteria and provide data reference for the subsequent fermentation experiments.The strain was grown for 18 h,the maximum concentration of bacteria was 0.683 g/L.It was a good conversion rate of lactic acid was 85%at the end of fermentation by using MRS culture medium.And for the carbon sources such as glucose,fructose,maltose,and other carbon sources,there was a higher intake rate and the conversion rate of acid producing.However,the sugar tolerance of the strain was not high.When the sugar concentration was 10 g/L-30 g/L,the concentration of bacteria decreased sharply,while the growth period of the strain was prolonged when the sugar concentration was 80 g/L.It was deduced preliminarily that the optimum fermented with the concentration range of sugar was 10 g/L-30 g/L.?2?Food waste was collected,preparing dry powder and analyzing its components.Among them,starch content and total sugar accounted for 49.5%,15.3%and 63%of dry base of food waste,respectively.Both of total solid?TS?and the volatile solid?VS?were89.15%and 80.79%respectively.And the value of VS/TS was 90.62%.The group of data shows that the collection of kitchen waste can provide a rich organic component for microbes,and it is a suitable fermentation material.?3?Then,in order to make the nutrient in the material directly used by the microorganism,food waste is properly pretreated.In order to increase the quality of carbon source for fermentation microorganism,we designed and optimized the experimental conditions of optimizing starch with double enzyme saccharification.The orthogonal experiment of 3 factors and 4 levels was designed based on the amount of liquefaction enzyme,glucoamylase and action time.The best combination was A₂B₁C₂D₃(liquefaction enzyme addition 10 U/g,liquefaction time 30 min,saccharifying enzyme dosage 300 U/g and saccharification time 150 min.On the other hand,in order to increase the soluble material in the water phase,the material can be pretreated by acid-ultrasonic method to facilitate the absorption and utilization of microbes and increase the fermentation product.The four optimization parameters of orthogonal experiment were ultrasonic time,ultrasonic power,acid catalyst concentration and a ratio of material to liquid.The best combination was A₂B₂C₁D₂ that ultrasonic power 450 W,ultrasonic time 8 min,acid catalyst concentration 0.05 M,and liquid ratio 1/6.Finally,in order to explore the synergistic effect of the coupling pretreatment,an acid-ultrasound assisted double enzyme was used to pretreat the material.The different pretreatment materials were measured by measuring the qualities of soluble substance and glucose,representational structure.According to the above results it can be concluded that something advantages of fermentation.?4?In order to obtain the optimal combination of open fermentation,the optimization of fermentation conditions,strain types,and the fermentation effect of different pretreatment materials,which was judged as criteria.The experimental results were as follows:the most important conditions for open fermentation were the ratio of material to liquid was 1/6,inoculum 9%bacteria solution,pH value was 7 and 30?,and anaerobic incubation was 10 days.The highest concentration of lactic acid in MO₂ group was 46.67g/L,and the conversion rate of lactic acid was 70.88%.The highest value of MO₂ group was 1.72 times higher than that of MO₁ group?control group?,that is,the open anaerobic fermentation of unacclimated strain by acid ultrasonic pretreatment was the best combination of open fermentation under this condition.?5?Through this experiment,to find the initial concentration of substrate,a buffer that regulates pH,different pretreatment materials such as optimization of fermentation results,and the fed batch fermentation of optimal fermentation conditions:initial substrate concentration of 27%,high sugar group strains inoculation domestication materials saccharification-acid-ultrasonic pretreatment,feeding cycle per 72 h fill volume concentration the material.The maximum lactic acid concentration of 29.89 g/L was obtained at the end of the fermentation,and the conversion rate of lactic acid was 57.52%,which was 39.43 times over the initial lactic acid concentration.