Biological Pretreatment Of Corn Stover And Study On Change Rule Of Lignocellulose

Com stover is one of the important material for anaerobic fermentation.Due to the complex structure,main components about cellulose,hemicellulose,and lignin are speed limit factors for the anaerobic fermentation.In order to solve this problem,this study conducted biological pretreatment research,and optimized the pretreatinent process.For further understanding lignocellulose conversion rule,we analyze the infrared spectrum and X-ray diffraction in the process of pretreatment,and combined with PCR-DGGE technology for microbes dynamic change analysis to further elaborate material transformation rule.The main contents and results are as follows:(1)With corn stover as raw material,the biological experiment was carried out.In the biological pretreatment,selecting pretreatment time,concentration of cellulose degradation bacteria,biogas residue and corn stover TS ratio as factors,the three factors and five levels orthogonal experiment was carried out,and dry anaerobic fermentation was conducted after the pretreatment.The results showed that the affecting factors on cumulative gas production were,in turn,pretreatnent time,concentration of cellulose degradation bacteria and TS ratio.The best gas production was under conditions of pretreatment 7 day.10%degradation bacteria and 6:8 of TS ratio.(2)The content of cellulose,hemicellulose and lignin were determined during the pretreatment about 0%?2.5%?5%?7.5%and 10%groups.The results showed that cellulose,hemicellulose and lignin were degraded gradually.Compared to lignin,hemicellulose and lignin were easily degraded,and the degradation ratio could reach to 33.09%and 32.3%.(3)Infrared spectrum was explored during the pretreatment about 0%?2.5%?5%?7.5%and 10%groups.The results indicated that peak shape shifted a little,but the absorption of peak were profound changed.In 0?3 d,-OH of 3351 cm-1 in the cellulose was significantly different from beta-D-glycosidase of 898 cm-1,C-H of 873 cm-1 and C-O of 1164 cm-1 in cellulose.However,each functional group had periodic change.In hemicellulose,the absorption of peak at 1730 cm-1 was disappeared during the alkali pretreatment.In 0?7 d,the link of sugar units of 1048 cm-1 was destroyed gradually.Aromatic rings of 1512 cm-1 in lignin was difficult to degraded compared to other functional groups.(4)X-ray diffraction was explored during the pretreatment about 0%?2.5%?5%?7.5%and 10%groups.The results indicated that crystalline areas and amorphous areas of corn stover were destroyed,and calcium salt and silicate materials to maintain cell wall structure were also degraded.The damage of crystallization areas and bacteria concentration were positively correlated.The relative crystallinity of 10%group was continuely decreased,and the amorphous areas were almost disappeared on day 15.(5)PCR-DGGE was explored on day 0,3,7,and 15 about five treatment groups.The results indicated that Microbial of lignocellulose degradation were mainly Bacillus,Flavobacterium,Xanthomonas,Pseudomonas,Streptomycete and Clostridium,et al.during the pretreatment.Dominant species of each treatment group showed difference in different stage,and the evolutionary changes is accordance with degradation of cellulose,hemicellulose and lignin.