Microbial biomass and community structure of a phase-separated methanogenic reactor determined by lipid analysis

Abstract

An anaerobic phase-separation biomass reactor was established on cellulose with the hydrolysis and fermentation steps occurring in the first stage, and acetogenesis and methanogenesis in the second stage. Based upon lipid biomarker analysis, eubacterial and eukaryotic cells accounted for approximately 6% of the volatile solids of the first stage and 17% of the second, while methanogens were approximately 1% of the volatile solids in the first stage and 9% of the second. Clustering the polar lipid fatty acids into groups based upon their distributions between the two stages of the reactor clarified the differences in community structure caused by phase-separated operation. Although inoculated from the same source, the two stages maintained very different microbial communities. Signature fatty acids known as indicators of unbalanced growth in eubacteria were significantly higher in the first stage of the reactor. © 1992 Society for Industrial Microbiology.