A Comparative Study On Prokaryotic Microbial Diversity Of Biogas Digesters In Tropical And Subtropical Households In Yunnan Province

Currently, people have limited understanding of the problem on microbialcommunity structure, composition and dynamics of biogas fermentation systemunder different geographical regions and climatic conditions, and its correlation withenvironmental biotic and abiotic factors, namely the awareness of the ecologicalbasic problem of biogas fermentation system is not comprehensive enough. Inresponse to these problems, combined with the unique geographical, climaticadvantages and features of biogas fermentation application in Yunnan, and a goodbasis for the preliminary work, In this paper, culture-independent approaches(PCR-DGGE and16S rDNA clone technology) are used to systematicallycomparative analysis the prokaryotes community structure, composition anddynamics of rural household biogas digesters in tropical and subtropical typicalclimate regions of Yunnan, and analyzed its correlation with environmental bioticand abiotic factors, then discussed the main factors which effect the prokaryotescommunity temporal dynamics of different digester, and reasons for the differencesin the microbial population between different digesters. Specific studies and researchresults are as follows:⑴preliminary analysis of prokaryotic microbial diversity in householdbiogas digesters by DGGE: DGGE was used to conducted a preliminary analysis ofprokaryotic microbial diversity of household biogas sludge in Yunnan (north)Tropical and (south) subtropical climate regions, the results show bacteria have aricher diversity than archaea, the differences of archaea diversity in biogas digestersare smaller than bacteria in the same climate zone, differences in bacterial diversityand differences in archaea diversity of different digesters in subtropical (Jianshui)were less than the tropics (Jinghong); digesters’ bacterial and archaea diversity indifferent climatic regions show different clustering case due to different digestersfermentation state, raw materials, feed situation, active time and so on. The maindifference in bacterial diversity may be related with the fermentation material, active time, the pool temperature and other factors, and differences in archaea diversity wasless affected by fermentation parameters. Moreover in the fermentation broth onlyCOD content was significantly negatively correlated with Archaea diversity, otherphysical and chemical factors have a smaller affect on bacteria and archaea diversity.⑵Prokaryotic microbial diversity analysis of household biogas digesters by16S rDNA clone technology:16S rDNA clone library was used to conducted ain-depth research on bacteria and archaea diversity of representative digester inYunnan (north) Tropical and (south) subtropical climate regions, the results showboth two climatic regions of rural household biogas digesters have extensivediversity of archaea and bacteria, and bacterial diversity was significantly higherthan archaea; statistical analysis show most bacteria of the biogas fermentationsystem in two climatic regions are uncultured, both predominant bacterial groups areBacteroides, Chloroflexi, Firmicutes and Proteobacteria; predominant archaea groupis Methanosaeta of Methanosarcinales; In addition, a small amount of unculturedCrenarchaeota is detected; the differences in digesters’ bacterial diversity andarchaea diversity impact by the raw materials, active time, COD content and otherfactors.⑶Preliminary analysis on prokaryotic microbial diversity of the householdbiogas digesters with different fermentation status in different seasons:①directmicroscopic count method was used to count and morphological observation thebacteria rural household biogas digesters at different fermentation status (normal andabnormal fermentation) in different seasons (winter and summer) and differentclimatic regions (Jinghong and Jianshui), the results showed that the number ofbacteria in the abnormal fermentation sample is significantly more than normalfermentation samples, the number of bacteria in summer is more than winter samples;②bacterial and archaea diversity change were preliminary monitored and comparedby DGGE, the results showed that: there are some differences in the samples ofdifferent climatic regions, different seasons (winter and summer), normal andabnormal fermentation, Factors that affect whether the biogas fermentation normalmay mainly bacteria, rather than the archaea.On the one hand these results provide a theoretical guidance for the design and build of efficient biogas systems in representative area of Yunnan, on the other handto lay the foundation of related microbial resources collection, preservation, researchand utilization of Yunnan biogas fermentation.