The roles of acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of biomass to methane: a review

Abstract

Among different conversion processes for biomass, biological anaerobic digestion is one of the most economic ways to produce biogas from various biomass substrates. In addition to hydrolysis of polymeric substances, the activity and performance of the methanogenic bacteria is of paramount importance during methanogenesis. The aim of this paper is primarily to review the recent literature about the occurrence of both acetotrophic and hydrogenotrophic methanogens during anaerobic conversion of particulate biomass to methane (not wastewater treatment), while this review does not cover the activity of the acetate oxidizing bacteria. Both acetotrophic and hydrogenotrophic methanogens are essential for the last step of methanogenesis, but the reports about their roles during this phase of the process are very limited. Despite, some conclusions can still be drawn. At low concentrations of acetate, normally filamentous Methanosaeta species dominate, e.g., often observed in sewage sludge. Apparently, high concentrations of toxic ionic agents, like ammonia, hydrogen sulfide (H 2 S) and volatile fatty acids (VFA), inhibit preferably Methanosaetaceae and especially allow the growth of Methanosarcina species consisting of irregular cell clumps, e.g., in cattle manure. Thermophilic conditions can favour rod like or coccoid hydrogenotrophic methanogens. Thermophilic Methanosarcina species were also observed, but not thermophilic Methanosaetae. Other environmental factors could favour hydrogentrophic bacteria, e.g., short or low retention times in a biomass reactor. However, no general rules regarding process parameters could be derivated at the moment, which favours hydrogenotrophic methanogens. Presumably, it depends only on the hydrogen concentration, which is generally not mentioned in the literature.

Methanogenic community composition in an organic waste mixture in an anaerobic bioreactor

“…For these samples, the volume of biogas decreased, and the concentration of CH 4 in the biogas was lower than 60% (Table 3). The function of hydrogenotrophic methanogens is extremely important in the anaerobic use of simple soluble compounds; however, their role in biomass processing of complex organic compounds is poorly understood (Demirel and Scherer, 2008). The samples (FM4-FM7) collected under the longer waste retention times (29-47 days), which are characterised by higher abundance of Methanosaeta, are known to utilise acetate as the only substrate for methanogenesis.…”

A new upgraded biogas production process: Coupling microbial electrolysis cell and anaerobic digestion in single-chamber, barrel-shape stainless steel reactor

“…It was found that the dominant microbes on both anodes of E1 and E2 were hydrogenotrophic methanogens including 5 genus, Methanocorpusculum, Methanospirillum, Methanobacterium, Methanobrevibacter and Methanoculleus [16] (Fig. 2).…”

Biogas production from undiluted chicken manure and maize silage: A study of ammonia inhibition in high solids anaerobic digestion

“…Of particular importance is its application to the treatment of animal wastes where it can play a significant role in minimising the uncontrolled emission of methane to the atmosphere, thus reducing the impact of greenhouse gases associated with livestock management. The microbiology of the process relies on a number of interdependencies which allow a variety of complex organic materials to be converted to methane through the processes of hydrolysis, acidogenesis, acetogenesis, hydrogenogenesis and methanogenesis (Demirel & Scherer, 2008).…”