Bioaugmentation for Improved Recovery of Anaerobic Digesters After Toxicant Exposure

Bioaugmentation was investigated as a method to decrease the recovery period of anaerobic digesters exposed to a transient toxic event. Two sets of laboratory-scale digesters (SRT = 10 days, OLR = 2 g COD/L-day), started with inoculum from a digester stabilizing synthetic municipal wastewater solids (MW) and synthetic industrial wastewater (WW), respectively, were transiently exposed to the model toxicant, oxygen. Bioaugmented digesters received 1.2 g VSS/L-day of an H2-utilizing culture for which the archaeal community was analyzed. Soon after oxygen exposure, the bioaugmented digesters produced 25–60% more methane than non-bioaugmented controls (p \u3c 0.05). One set of digesters produced lingering high propionate concentrations, and bioaugmentation resulted in significantly shorter recovery periods. The second set of digesters did not display lingering propionate, and bioaugmented digesters recovered at the same time as non-bioaugmented controls. The difference in the effect of bioaugmentation on recovery may be due to differences between microbial communities of the digester inocula originally employed. In conclusion, bioaugmentation with an H2-utilizing culture is a potential tool to decrease the recovery period, decrease propionate concentration, and increase biogas production of some anaerobic digesters after a toxic event. Digesters already containing rapidly adaptable microbial communities may not benefit from bioaugmentation, whereas other digesters with poorly adaptable microbial communities may benefit greatly

Methyl Coenzyme M Reductase (mcrA) Gene Abundance Correlates with Activity Measurements of Methanogenic H2/CO2-Enriched Anaerobic Biomass

Biologically produced methane (CH4) from anaerobic digesters is a renewable alternative to fossil fuels, but digester failure can be a serious problem. Monitoring the microbial community within the digester could provide valuable information about process stability because this technology is dependent upon the metabolic processes of microorganisms. A healthy methanogenic community is critical for digester function and CH4 production. Methanogens can be surveyed and monitored using genes and transcripts of mcrA, which encodes the α subunit of methyl coenzyme M reductase – the enzyme that catalyses the final step in methanogenesis. Using clone libraries and quantitative polymerase chain reaction, we compared the diversity and abundance of mcrA genes and transcripts in four different methanogenic hydrogen/CO2 enrichment cultures to function, as measured by specific methanogenic activity (SMA) assays using H2/CO2. The mcrA gene copy number significantly correlated with CH4 production rates using H2/CO2, while correlations between mcrA transcript number and SMA were not significant. The DNA and cDNA clone libraries from all enrichments were distinctive but community diversity also did not correlate with SMA. Although hydrogenotrophic methanogens dominated these enrichments, the results indicate that this methodology should be applicable to monitoring other methanogenic communities in anaerobic digesters. Ultimately, this could lead to the engineering of digester microbial communities to produce more CH4 for use as renewable fuel

Proposal of \u3cem\u3eVibrionimonas magnilacihabitans\u3c/em\u3e gen. nov., sp. nov., a Curved Gram Negative Bacterium Isolated From Lake Michigan Water

A mesophilic bacterium appearing as curved rod-shaped cells was isolated from Lake Michigan water. It exhibited highest similarities with Sediminibacterium ginsengisoli DCY13T (94.4 %); Sediminibacterium salmoneum NJ-44T (93.6 %) and Hydrotalea flava CCUG 51397 T (93.1 %) while similarities with other recognized species were sym-homospermidine was the primary polyamine. The major cellular fatty acids were iso-C15 : 1G, iso-C15 : 0, iso-C16 : 0 3-OH and iso-C17 : 0 3-OH, with moderate amounts of iso-C16 : 0. The presence of glycolipids differentiated the novel strains from related genera. The DNA mol% G+C content of the type strain MU-2T was 45.2. Results for other phenotypic and molecular analyses indicated that strain MU-2T is a representative of a novel genus and species for which the name Vibrionimonas magnilacihabitans is proposed. The type strain is MU-2T ( = NRRL B-59231 = DSM 22423)