Activity of methanogenic biomass after heat and freeze drying in air†
It would be beneficial if methanogenic cultures could be preserved for anaerobic digester bioaugmentation or as seed for standard tests such as biochemical methane potential. However, storage of wet culture or drying in anaerobic atmosphere may not be economically feasible. In this study, the effect of heat and freeze drying in ambient air on the methanogenic activity of an anaerobic culture was determined. The anaerobic culture was dried in air at 104 °C for 12 h, and by freezing at −196 °C in air with subsequent drying at subzero temperatures. The rehydrated culture consistently produced CH4 from H2:CO2 and acetate after drying. Drying caused a greater decrease in acetate methanogenic activity compared to H2:CO2 methanogenic activity. Transcript qPCR results for a functional gene in methanogens (mcrA) also revealed significant survivability of rehydrated methanogenic populations. Inactivation due to drying differed among genera, with least to most inactivation in the order Methanospirillum < Methanosaeta < Methanoculleus.