Anaerobic Degradation Characteristics Of Cellulose And Analysis Of Functional Microorganisms

Agricultural waste contains a large amount of cellulose,which has become the popular raw material for producing biofuel due to its low cost and sustainable supply.However,the high cellulose polymerization and the special crystalline structure resulted in cellulose was difficultly degraded.In order to improve the utilization of cellulose,this study uses sodium carboxymethyl cellulose as the sole carbon source,and anaerobic granular sludge from papermaking wastewater and rumen materials as inoculum sludge for anaerobic degradation of cellulose.This study design 5 co-inoculation ratios of granular sludge and rumen material(11:1,5:1,7:2,5:2,2:1)to investigate the influence of different ratios on cellulose anaerobic fermentation.The results showed that the cumulative methane production and COD removal were increased first and then decreased with the increase in rumen materials.At a ratio of 5:1,the cumulative methane production and COD removal reached maximum(58.64 m L and 42.2%).Ethanol,acetate,propionate,butyrate,and valerate were recognized as main liquid terminal products.The fermentation type gradually changed to mixed acid-fermentation from butyrate-fermentation with increase in rumen materials.In addition,rumen material significantly increased the diversity of microorganisms.The effect of the initial pH on the anaerobic degradation of cellulose by the co-inoculation flora indicated that the alkaline conditions with the initial pH of 7.5 to 10.0 was favorable for methanogenesis.Among them,the highest cumulative methane production and COD removal were obtained at initial pH 8.0.They were 202.3 m L and 59.3%,respectively.When the initial pH is 4.0,the acidification of the reactor could be observed.At the range of initial pH 4.5?7.0,the methane production,total acid removal and COD removal were increased with pH increase.Propionate was easily generated at initial pH 5.5.The results of anaerobic fermentation of cellulose mediated by different redox mediators showed that GO,methyl-violet,humus and henna quinone had a certain promotion effect.Among them,GO could significantly enhanced cellulose degradation and the cumulative methane production and COD removal were higher than that of control by 10%.The riboflavin could significantly promote the hydrolysis and fermentation,but it inhibit the activity of hydrogen-producing acetogens and methanogens,resulting in excessive accumulation of volatile acid(VFAs)and acidification of the reactor.In addition,the present study also found that GO could improve the activity of hydrogen-producing acetogens degrading butyrate in the fermentation system,thereby making butyrate was completely degraded.GO could significantly promote hydrolysis and fermentation.Propionate was decreased while butyrate was increase with GO increase.When the GO concentration was 25-80 mg/L,the cumulative methane production and COD removal were similar to that of control.Under GO of 120?180 mg/L conditions,the cumulative methane production and COD removal were increased with GO increase.The maximum were achieved at the GO of 180mg/L.The cumulative methane production and COD removal rate were increased by 8.7% and 8.8%,respectively.Microbial community structure showed that low concentrations of GO would promote the abundance of hydrolyzed and fermentation bacteria such as Mesotoga and Treponema.Their abundance was decreased with the increase of GO,whereas the abundance of unclassified bacteria related to methanogenesis was gradually increased.