Figure 3.

Longitudinal monitoring of the utilization of ethanol or H₂ (a) and methanol (b), as well as the formation of acetate (c) and methane (d) in batch cultures of Methanosphaera sp. WGK6 and M. stadtmanae DSMZ 3091^T when provided with either methanol and hydrogen or methanol and ethanol. As expected methanol and hydrogen utilization, as well as methane formation, was observed for both WGK6 and DSMZ 3091^T, when cultured using this substrate combination (▴ and ▾ for WGK6 and DSMZ 3091^T, respectively). However, only strain WGK6 (•) and not DSMZ 3091^T (▪) demonstrated an ability to utilize both methanol and ethanol to support methane formation (and growth, as depicted in Figure 2). In addition, acetate accumulation over time was only evident when strain WGK6 was cultured with both methanol and ethanol, suggesting a two-step oxidation of ethanol can provide the reducing power required for methanol reduction and methanogenesis (and growth) in the absence of H₂. With the exception of the results for ethanol measurements presented in Figure 2a, the results represent the mean values obtained from duplicate experiments.