Effects of physical treatment on microbial communities in seed cultures for methane production from food waste. sludge metagenome

The freeze-thaw process helped improve the settling characteristics of the sludge which should help decouple hydraulic retention time and solid retention time of a stirred tank reactor. From the tagged 16S rRNA gene pyrosequencing analysis, the freeze-thaw process had the effect on the overall bacterial community structure. Selective enrichments of some bacterial phyla were found both in the solid and the liquid fractions of the frozen-thawed sludge. Enhanced acidogenic activity of the solid fraction was in good agreement with the enrichment of Clostridiaceae, Porphyromonadaceae and Propionibacteriaceae in the sample. Both changes in the sludge settling characteristics, the microbial activities and the bacterial community structure indicated that the solid fraction of the frozen-thawed sludge became a better inoculum for anaerobic hydrogen production. The selective enrichments of Oxalobacteraceae, Moraxellaceae and Pseudomonadaceae were found in the liquid fraction of the frozen-thawed sludge. Since some bacterial species in Oxalobacteraceae and Moraxellaceae have been reported to have hydrolytic activities, potential application of the liquid fraction should be further investigated.