Research On PHA Production Technology Using Anaerobic Fermentation Slurry Of Restaurant Food Waste As Substrate

Restaurant food waste is rich in organic matter,and it is a waste resource with high utilization value.At present,anaerobic fermentation is mainly used to treat restaurant food waste and produce biogas,but the anaerobic fermentation slurry produced in this process is difficult to treat and may pollute the environment.The anaerobic fermentation slurry of restaurant food waste contains abundant carbon sources,which can be synthesized into polyhydroxyalkanoates(PHA),a kind of biodegradable plastic material through the action of specific microorganisms.It can reduce pollution and realize the recycling of resources at the same time.In this study,based on the systematic study of the microbial diversity of anaerobic fermentation slurry in a typical kitchen waste treatment plant in Hebei Province,the main application types of PHA,PHB and PHV,were selected as the analysis objects,screened microbial strains which can synthesize PHA efficiently,and the fermentation conditions and technical parameters of microbial synthesis of PHA were optimized.This study could provide reference for the treatment and resource utilization of anaerobic fermentation slurry of restaurant food waste.The main results were as follows:1.The physicochemical properties and high-throughput Miseq sequencing analysis showed that the microbial community structure in the main process unit of the restaurant food waste treatment was affected by environmental factors,with pH and ammonia nitrogen content as the major influencing factors,oil content and total sugar content had more stable effects on the microbial community structure,followed by total salt content and COD.The microbial composition and relative abundance in the anaerobic digestion and biogas residue dehydration samples were higher,while the microbial community species and abundance in the initial oil-water separation samples were relatively lower.The dominant phylum and genus in different seasons were similar,but the relative abundance changed obviously.Among the main process units,the main dominant bacteria were Firmicutes,Bacteroidetes,and Chloroflexi,Synergistetes,etc.,the dominant genus were Lactobacillus,Syntrophomonas,Fastidiosipila,vadinBC27 waste-sludge_group,etc.After comprehensive analysis,the waste liquid of anaerobic digestion process unit was selected for resource reuse to produce PHA.2.Based on the results of microbial diversity of restaurant food waste fermentation slurry,a PHA-producing strain BW-2 was screened from the waste liquid in the anaerobic digestion process unit of restaurant food waste by bromothymol blue staining.After 16S rRNA sequence analysis,it was initially identified as Alcaligenes faecalis,which could accumulate 10.21 mg/L PHB when inoculated into anaerobic fermentation slurry directly.In order to facilitate the accumulation of PHB and PHV,the parameters of anaerobic fermentation slurry were preliminarily adjusted as follows:C/N ratio was 48,0.015%alpha-amylase and 0.12%lipase were added to hydrolyze excess starch and fat,and adjusted the pH to 7.5.3.The screened strain BW-2 was proportionally mixed with three other strains CGMCC 1.3716,CGMCC 1.6329 and CGMCC 1,7092 and inoculated into anaerobic fermentation slurry to optimize the fermentation conditions of PHB and PHV.The "time-temperature-inoculation amount" was selected for the three-factor and three-level response test.The results showed that the interaction between fermentation time and temperature,temperature and inoculation amount had significant effects on the yield of PHB,the interaction between fermentation time and temperature,fermentation temperature and inoculation amount had significant effects on the yield of PHV.At 35?,fermentation for 84 h,the inoculation amount of each strain was 2.0%,the highest PHB production was 153.84 mg/L;at 30?,fermentation for 108 h,and the inoculation amount of each strain was 1.0%,the highest PHV production was 1421.37 mg/L.At this time,the total yield of PHB and PHV was also the highest,which was 1517.69 mg/L.4.Different methods were used to extract PHB and PHV from the btoth of each strain,the sodium hypochlorite-chloroform method had the best effect on extracting PHB and PHV,with the extraction rates of 60.02%and 61.03%respectively,followed by surface active agent method,with the extraction rates of 56.91%and 57.65%respectively.Based on the analysis of microbial diversity in the treatment process of restaurant food waste,BW-2 strain was screened to synthesize PHA,and the optimum technological conditions for the synthesis of PHB and PHV from anaerobic fermentation slurry of restaurant food waste were explored.This study could provide scientific parameters for the treatment and resource utilization of restaurant food waste in China.