Physiology and methane productivity of Methanobacterium thermaggregans

Abstract

Accumulation of carbon dioxide (CO2), associated with global temperature rise, and drastically decreasing fossil fuels necessitate the development of improved renewable and sustainable energy production processes. A possible route for CO2 recycling is to employ autotrophic and hydrogenotrophic methanogens for CO2-based biological methane (CH4) production (CO2-BMP). In this study, the physiology and productivity of Methanobacterium thermaggregans was investigated in fed-batch cultivation mode. It is shown that M. thermaggregans can be reproducibly adapted to high agitation speeds for an improved CH4 productivity. Moreover, inoculum size, sulfide feeding, pH, and temperature were optimized. Optimization of growth and CH4 productivity revealed that M. thermaggregans is a slightly alkaliphilic and thermophilic methanogen. Hitherto, it was only possible to grow seven autotrophic, hydrogenotrophic methanogenic strains in fed-batch cultivation mode. Here, we show that after a series of optimization and growth improvement attempts another methanogen, M. thermaggregas could be adapted to be grown in fed-batch cultivation mode to cell densities of up to 1.56 g L−1. Moreover, the CH4 evolution rate (MER) of M. thermaggregans was compared to Methanothermobacter marburgensis, the CO2-BMP model organism. Under optimized cultivation conditions, a maximum MER of 96.1 ± 10.9 mmol L−1 h−1 was obtained with M. thermaggregans—97% of the maximum MER that was obtained utilizing M. marburgensis in a reference experiment. Therefore, M. thermaggregans can be regarded as a CH4 cell factory highly suited to be applicable for CO2-BMP.Electronic supplementary materialThe online version of this article (10.1007/s00253-018-9183-2) contains supplementary material, which is available to authorized users.

Hyperthermophilic methanogenic archaea act as high-pressure CH4 cell factories

“…4 ). M. thermaggregans , which is a high CH 4 productivity strain in fed-batch cultivation mode 13 , did not grow at 50 bar (Supplementary Fig. S12 ) and M. villosus and M. igneus showed a decrease of MER and turnover rate directly in RCB2 (Fig.…”

“…The CO 2 -BMP process can be employed in multiple applications such as biogas upgrading, power-to-gas applications, decentralized energy production, and for the conversion of H 2 /CO 2 of process flue gasses in waste to value concepts from, e.g., ethanol, petroleum, steel, and chemical industries 10 . There are two main approaches for CO 2 -BMP 11 : ex situ biomethanation using pure cultures 12,13 or enriched mixed cultures [14][15][16] , and in situ biomethanation 17,18 . In situ biomethanation is examined for upgrading the CH 4 content of biogas by adding H 2 to anaerobic digesters.…”

Development of a simultaneous bioreactor system for characterization of gas production kinetics of methanogenic archaea at high pressure

“…Waste to value approaches, also renewable electricity, for conversion into methane (CH 4 ) [1][2][3][4]. One example is the CO 2 -based biological CH 4 production process [5][6][7][8]. Here, CO 2 -type hydrogenotrophic methanogens from the domain of archaea utilize H 2 and CO 2 as a carbon and energy source to autocatalytically produce CH 4 , water (H 2 O), and biomass X (g L −1 ) according to Equation (1).…”

Methods for quantification of growth and productivity in anaerobic microbiology and biotechnology

“…The quantification of biomass dry or wet weight can be correlated to other biomass quantification approaches such as spectrophotometry. Furthermore, for improving bioprocess quantification, the elementary composition of biomass can be determined (Mauerhofer et al 2018 ) to balance growth stoichiometry on an elemental molar basis.…”

“…The operation of a drum-type gas meter is based on the displacement principle to elucidate the gas flow. During fed-batch cultivations of Methanobacterium thermaggregans , the gas flow was experimentally determined via a TG3 plastic drum-type gas meter (Mauerhofer et al 2018 ). This device can be operated in offline and online mode.…”