The Variation Of Hydrolase Activity And Microbial Community During Acclimation Process Of Inoculum Used As Biogas Fermentation Of Food Waste

The treatment of food waste has become one of the serious worldwide issues.Biogas fermentation is increasingly considered to be a promising treating method,it can not only improve the environment,but also solve the problem of energy shortage.Nonetheless,there were several problems in the process of biogas fermentation treating food waste,such as instability,acidification and low rate of gas.The quality of inoculum is important for the stable process of biogas fermentation.In order to improve the stability of food waste biogas fermentation,inoculum were acclimated by adding different food waste and phosphate concentration,and the variation of daily biogas production,hydrolase activity and microbial community structure during inoculum acclimation process were monitored.To investigate the effect of different acclimated inoculum on capacity of producing biogas in biogas fermenter of food waste,batch fermentation of food waste were conducted with different acclimated inoculum.In order to find best acclimated condition,comprehensive comparison of hydrolase activity,microbial community and the capacity of producing biogas in different acclimated inoculum.This study lay the foundation for stable operation of food waste biogas fermentation.The following results were obtained:1?The variation of daily biogas production during acclimation process was monitored.The result showed that the higher feeding intensity and phosphate concentration could accelerate the acclimation,but excessive feeding intensity and phosphate concentration could undermine the stability process of acclimation.In order to improve the speed of acclimation and guarantee stability process of acclimation,adding 1g/d food waste and 1360 mg/L KH2PO4 is optimum acclimation method.2?The capacity of producing biogas of acclimated inoculum in biogas fermenter of food waste was monitored.The result showed that inoculum acclimated with adding food waste and phosphate were used as inoculum of biogas fermentation of food waste,which could make biogas fermentation of food waste run smoothly.The feeding intensity,phosphate concentration and acclimation time both significantly affect capacity of producing biogas of inoculum in biogas fermenter of food waste.Inoculum stem from stability process of acclimation were used as biogas fermentation of food waste,which is optimum inoculum.Inoculum acclimated with adding 1g/d food waste,1360 mg/L KH2PO4 and duration of 15 th is more suitable for biogas fermentation of food waste.3?The variation of hydrolase activity during acclimation process was monitored.The result showed that adding food waste and phosphate could improve protease activity,amylase activity,cellulase activity and lipase activity of inoculum.The feeding intensity,phosphate concentration and acclimation time both significantly affect hydrolase activity.The higher hydrolase activity could enhance the start-up of biogas fermentation of food waste and improve biogas-producing efficiency.Inoculum acclimated with adding 1g/d food waste,1360 mg/L KH2PO4 and duration of 15 th contain high hydrolase activity.4 ? The variation of microbial community during acclimation process was monitored by Illumina Mi Seq technology.The main result as follow:(1)The dominant microbial of inoculum acclimated with adding food waste and phosphate were Bacteroidetes,Proteobacteria,Firmicutes,Chloroflexi,Euryarchaeota;the subdominant microbial were Spirochaetes,Planctomycetes,OP3,Fusobacteria,Crenarchaeota,Synergistetes;Methanogens included Methanobacterium,Methanocorpusculum,Methanosaeta,Methanosarcina and Methanocalculus;(2)Inoculum acclimated with adding food waste and phosphate could not only improve microbial diversity,but also enhance the growth of microorganism associated with degradation of food waste,such as dominant microbial included Bacteroidetes,Chloroflexi,Firmicutes,Fusobacteria,Synergistetes;methanogens included Methanobacteria and Methanomassiliicoccaceae;hydrolytic bacteria included Clostridium,Bacteroides,Butyrivibrio,Proteiniclasticum and Sedimentibacter;(3)The feeding intensity,phosphate concentration and acclimation time both significantly affect microbial diversity and composition.Microbial composition gradual changed during acclimation time in order to adapt to degradation of food waste.The higher feed intensity and phosphate concentration could accelerate the change of microbial composition of original inoculum.Inoculum acclimated with adding 1g/d food waste and 1360 mg/L KH2PO4 contain high microbial diversity;(4)Pearson correlation analysis revealed that the number of OTU and the relative abundance of Firmicutes and Fusobacteria were both positively correlated with biogas production.The high abundance microbial commnuity was beneficial to the degradation of food waste.Firmicutes and Fusobacteria were closely related to the capacity of biogas-producing of food waste.(5)In this study,some unclassified microorganisms of E2 may be associated with methane-producing.5?The study of the relationship between the varation of daily biogas production,hydrolase activity and mictobial community during acclimation process.The daily biogas production,hydrolase activity and mictobial community could be used as elevation index of the quality of inoculum.When daily biogas procuction tend to stable during acclimation process of inoculum,as well as contain high hydrolase activity and mictobial diversity,which was optimum acclimated inoculum for using to degradation of food waste.