Resource Utilization Of Food Waste Based On Biocatalytic Conversion

With the development of society and the increase in population,the disposal of food waste has gradually become a global problem.Traditional incineration and landfill treatment will produce secondary pollution and affect the ecological environment,composting and fermentation gas production processes also have many defects;therefore,how to realize the resource utilization of food waste in a green and efficient manner has become a research hotspot at home and abroad.This subject is aimed at the defects of the existing technology,based on biocatalytic conversion,using microbial fermentation technology to convert food waste into high value-added industrial chemicals.However,food waste has a complex composition and high water content,previous studies have also proved that the ability of microorganisms to directly utilize food waste is weak,and hydrolysis pretreatment can significantly improve its bioavailability.In view of the above problems,this paper studies and optimizes the hydrolysis pretreatment process of food waste,then,the process of Rhizopus arrhizus using hydrolysate fermentation to produce fumaric acid is optimized.The specific research content and conclusions are as follows:1.Determine the process route for the two-step hydrolysis pretreatment of food waste.Commercialized liquefaction enzymes and saccharification enzymes are used to treat food waste.After two-step enzymatic hydrolysis,the glucose concentration in the hydrolysate is increased from the initial 0.21 g/L to 33.79 g/L,the hydrolysate is used to ferment to produce acid and the content of fumaric acid Reach 8.74 g/L.In response to the high price of enzyme preparations,a process of replacing liquefied enzymes with thermal hydrolysis to pretreat food waste was developed.Through single-factor experiments and orthogonal experiments,the optimal process conditions for thermal hydrolysis were determined as follows:hydrolysis Temperature 130℃,hydrolysis time 60 min,reactant solid-liquid ratio 1:3(w/w),applied pressure 2 MPa(CO2 pressurized);under these conditions,the glucose content in food waste after thermal hydrolysis is 5.03 g/L.Combining thermal hydrolysis and glucoamylase treatment,after two-step hydrolysis treatment,the glucose concentration in the hydrolysate can reach 16.85 g/L.2.Rejuvenation and mutagenesis screening of fermentation strains.In view of the problem of low fermentation efficiency of strains,glucose is used as a carbon source to rejuvenate strains;the acid production of fermentation has been increased from 6.54 g/L to 26.06 g/L,the composition of the hydrolysate of food waste is complicated and the growth of strains is inhibited.In order to improve the tolerance of Rhizopus arrhizus strains to the hydrolysate,a combination of mutagenesis and pressure screening was used to screen the fermentation strains;a strain H-2 with strong acid production ability from the hydrolysate was obtained.Using this strain to produce acid by fermentation with hydrolysate as a carbon source,the maximum yield of fumaric acid was 7.86 g/L,and the space-time yield reached 0.114 g/(L·h).3.Comprehensive design of the acid production process of hydrolysate fermentation.In view of the biological toxicity of HMF and other by-products in the hydrolysate,the detoxification and concentration process of the hydrolysate was developed;after the detoxification treatment with activated carbon,the pigment content in the hydrolysate was significantly reduced,and the content of HMF was reduced from 4.85 g/L to 0.05 g/L,using the hydrolysate after detoxification to ferment to produce 8.25 g/L acid,which is higher than the 7.86 g/L before treatment.The concentration of reducing sugar in the hydrolysate was further increased through concentration treatment,and the final glucose concentration could reach 52.45 g/L;the acid production of the concentrated hydrolysate by fermentation could reach 15.62 g/L,which was 98.73%higher than that of the unconcentrated hydrolysate.