| The annual output of vegetable waste（VW）is huge.If it cannot be effectively disposed of,it will cause resource waste and environmental pollution.At present,the main processing method of disposal of landfill,incineration,composting,feed and anaerobic fermentation,by contrast,anaerobic fermentation has a big advantage,can realize vegetable waste reduction and recycling,the process to produce volatile fatty acids（VFAs）,has the high added value and broad application prospects.After solid-liquid separation of vegetable wastes,the large molecular organic matter（cellulose,hemicellulose,etc.）which is not easy to decompose remains in the solid,and the soluble small molecular organic matter（glucose,fructose,etc.）is transferred to the liquid,which creates conditions for the efficient production of VFAs by liquid anaerobic fermentation.This study on stems leafy vegetable waste liquid,the fruit vegetable waste liquid and mixed vegetable waste liquid as the substrate,anaerobic fermentation,explore the factors of production rate and conversion rate and the effect of VFAs and combination of microbial community structure and microstructure,clarify its reaction mechanism,provides the theory basis for vegetable waste VFAs production and high efficiency.Specific research results are as follows:（1）VFAs was produced by fermentation with BCWL as substrate,and the stacking time was 3 days.The proportion of BCWL and VFAs yield reached the maximum value,which were 79.62%and 187.79 mg COD/g VS,respectively.SEM also confirmed that the accumulation caused serious damage to the cellular structure of vegetable waste,and water and organic matter were easily released into BCWL.When the initial p H value was 7,the inoculation amount was 2 g TS/L,and the temperature was 35℃,the YIELD of VFAs was187.23 mg COD/g VS,and VFAs/SCOD was 75.81%.The main content of VFAs was acetic acid（94.86%）,which indicated that neutral conditions were favorable for hydrolysis.Proper inoculation and moderate temperature conditions can accelerate the formation of VFAs.The dominant bacteria in BCWL fermentation broth were Firmicutes（84.75%）,and the main genera were Lactobacillus（68.91%）,Lactococcus（6.99%）,Pediococcus（4.12%）and Buttiauxella（3.55%）.All of them are related to hydrolytic acidification of organic matter and are beneficial to the production of VFAs.（2）The yield of VFAs was 358.97 mg COD/g VS and 62.69%VFAs/SCOD when the initial p H value was 7,the inoculation amount was 3 g TS/L,the methane inhibitor（SBES）was 1 mmol and the temperature was 45℃for 96 h.VFAs was mainly acetic acid（93.81%）,which was acetic acid-producing fermentation,indicating that neutral conditions were favorable for hydrolysis,a small amount of SBES could inhibit the activity of methanogens,and proper inoculation and high temperature conditions accelerated the formation of VFAs.The maximum VFAs yields of tomato waste solid（TWS）,liquid（TWL）and solid+liquid（TWM）were 169.22 mg COD/g VS,361.53 mg COD/g VS and 251.27 mg COD/g VS at 144 h,96 h and 120 h,respectively.TWL had the highest VFAs yield.The proportions of C,H and O in TWS were 43.86%,5.98%and 48.77%,respectively,which were close to the molecular formula of polysaccharide((C6H10O5)n).The proportions of C,H and O in TWL were 39.79%,6.21%and 52.91%,respectively,which were close to the molecular formula of monosaccharide(C6H12O6).SEM showed that the density of bacteria in TWL fermentation broth sludge was large.It was confirmed that TWL contained more soluble small molecular organic matter,and the VFAs yield was increased and the fermentation time was shortened by using TWL as the substrate.Proteobacteria（45.39%）was the dominant phylum in the original fermentation broth,followed by Cyanobacteria Chloroplast（26.74%）and Firmicutes（8.52%）.At the end of fermentation,Firmicutes（96.81%）was the dominant phylum.Acetic acid was positively correlated with Firmicutes（0.9341）,while Cyanobacteria Chloroplast and Proteobacteria were negatively correlated with VFAs production（-0.7611 and-0.9341）.Streptophyta（26.74%）was the dominant genus,followed by Pantoea（23.88%）,Leuconost（7.23%）and Lactobacillus（6.35%）.At the end of fermentation,the dominant genus was Lactobacillus（87.21%）.Acetic acid was positively correlated with Lactobacillus（0.9579）.In the fermentation process,C cycle showed an increasing trend and reached 96.28%,while N cycle showed a decreasing trend and reached 3.17%.（3）Mixed vegetable waste liquid（VWL）was used to produce VFAs.When the initial p H was 7,the inoculation amount was 3 g TS/L,SBES was 1 mmol and the temperature was35℃for 96 h,the yield of VFAs was 325.81 mg COD/g VS,VFAs/SCOD was 66.22%,VFAs was mainly acetic acid（94.25%）,which was acetic acid-producing fermentation,indicating that neutral conditions were favorable for hydrolysis,a small amount of SBES could inhibit the activity of methanogens,and proper inoculation and high temperature conditions accelerated the formation of VFAs.The maximum VFAs yield of VWL and mixed vegetable waste（VWM）was 318.73 mg COD/g VS and 231.27 mg COD/g VS at 96 h and 120 h,respectively,and VWL had the highest VFAs yield.The proportions of C,H and O in mixed vegetable waste solids（VWS）were 43.76%,5.78%and 47.97%,respectively,close to the molecular formula of polysaccharide((C6H10O5)n);the proportions of C,H and O in VWL were39.33%,6.21%and 53.01%,respectively,close to the molecular formula of monosaccharide(C6H12O6).It was confirmed that VWL contained more soluble small molecular organic matter,which was used as the substrate to improve the VFAs yield and shorten the fermentation time.Proteobacteria（29.34%）was the dominant phylum in the original fermentation broth,followed by Cyanobacteria Chloroplast（27.09%）,Bacteroidetes（8.47%）and Firmicutes（7.69%）.Firmicutes（77.57%）were the dominant phylum.Streptophyta（31.09%）was dominant in the original fermentation broth,followed by Acinetobacter（9.61%）,Pseudomonas（4.22%）and Lactobacillus（5.63%）.The dominant bacterium was Lactobacillus（68.84%）,which was related to hydrolytic acidification of organic matter and conducive to VFAs production. |
