Effects of Temperature on Methanogenesis in a Thermophilic (58°C) Anaerobic Digestor

Abstract

The short-term effects of temperature on methanogenesis from acetate or CO2 in a thermophilic (58°C) anaerobic digestor were studied by incubating digestor sludge at different temperatures with 14C-labeled methane precursors (14CH3COO or 14CO2). During a period when Methanosarcina sp. was numerous in the sludge, methanogenesis from acetate was optimal at 55 to 60°C and was completely inhibited at 65°C. A Methanosarcina culture isolated from the digestor grew optimally on acetate at 55 to 58°C and did not grow or produce methane at 65°C. An accidental shift of digestor temperature from 58 to 64°C during this period caused a sharp decrease in gas production and a large increase in acetate concentration within 24 h, indicating that the aceticlastic methanogens in the digestor were the population most susceptible to this temperature increase. During a later period when Methanothrix sp. was numerous in the digestor, methanogenesis from 14CH3COOwas optimal at 65°C and completely inhibited at 75°C. A partially purified Methanothrix enrichment culture derived from the digestor had a maximum growth temperature near 70°C. Methanogenesis from 0CO2 in the sludge was optimal at 65°C and still proceeded at 75C. A C02-reducing Methanobacterium sp. isolated from the digestor was capable of methanogenesis at 75°C. During the period when Methanothix sp. was apparently dominant, sludge incubated for 24 h at 65°C produced more methane than sludge incubated at 60°C, and no acetate accumulated at 65°C. Methanogenesis was severely inhibited in sludge incubated at 70°C, but since neither acetate nor H2 accumulated, production of these methanogenic substrates by fermentative bacteria was probably the most temperature-sensitive process. Thus, there was a correlation between digestor performance at different temperatures and responses to temperature by cultures of methanogens believed to play important roles in the digestor.

[Conversion of acetic acid to methane by thermophiles]

“…We found slightly higher temperature optima for natural methanosenie populations in a 58°C reactor when we incubated them for short periods with 14C-labelled acetate, i.e. an optimum for methanogenesis from acetate near 58°C when Methanosarcina predominated and near 65°C when Methanothrix predominated [25].…”

“…Other thermophillic strains of Methanosareina have been isolated which grow optimally at 55 °C rather than 50 o C, including strains CHTI-S5 [24] and CALS-1 [25]. These strains can grow at 60°C, a temperature at which strain TM-1 cannot grow.…”

Metabolic, Phylogenetic, and Ecological Diversity of the Methanogenic Archaea

“…The most common aceticlastic methanogens in thermophilic digestors include Methanosarcina thermophila and thermophilic Methanosaeta. 43,137 The pH is another important parameter. Increases of loading rates lead to increases in the concentration of fatty acids and decreases in pH.…”

Comparative proteomic analysis of Methanothermobacter thermautotrophicus reveals methane formation from H2 and CO2 under different temperature conditions

“…However, methanogens can exhibit a diverse range of temperature adaptation. These environments can range from geothermal vents at temperatures greater than 100°C to oceans at temperatures below 4°C (Reid et al, 2006;Zinder, Anguish, & Cardwell, 1984). Methanogens are common in petroleum reservoirs with temperatures in the range from 20 to 80°C (Enoki, Shinzato, Sato, Nakamura, & Kamagata, 2011;Hendrickson et al, 2008;Kato, Kosaka, & Watanabe, 2008;Luo, Zhang, Suzuki, Hattori, & Kamagata, 2002;Nazina et al, 2006).…”