[Phylogenetic analysis of methanogenic corn stalk degrading microbial communities]

Methanogenic corn stalk degrading enrichment cultures were constructed using corn stalk as the sole carbon source and eight types of environmental samples as inocula. All the cultures could degrade corn stalk within 30-50 days and the total solids (TS) removal rates were in the range of 30%-40%. In six out of eight cultures, the cumulative methane yields per gram TS were 62.1-118.4 mL x g(-1), with acetate, propionate and butyrate as the major volatile fatty acids (100-500 mg x L(-1)), and the final pH were 6.5-6.7. In the other two cultures, the cumulative methane yields per gram TS were 8.5-9.7 mL xg(-1), while the concentrations of acetate were high (1200 mg x L(-1)), and the final pH were low (5.6-5.9). The bacterial and archaeal structures in eight enrichments were investigated with a 16S rRNA genes-based clone library method. Clones belonging to the bacterial phyla Firmicutes, Bacteroidetes, Synergistetes and Thermotogae were observed in abundance within the bacterial clone libraries, which accounted for 37.8%, 34.3%, 11.6% and 6.4% of the total number of bacterial clones, respectively. Within the domain Archaea, clones affiliated with the classes Methanomicrobia and Methanobacteria were found to be abundant in the archaeal clone libraries, which accounted for 61.1% and 38.9% of the total number of archaeal clones, respectively.