Methanogenesis: Are ruminants only responsible: A review

Abstract

Methane is a potent greenhouse gas with a global warming potential 25 times more than carbon dioxide. Methanogenesis is a multi-step process involving different group of micro-organisms like hydrolytic, fermentative, acetogenic and above all methanogenic micro-organisms. Methanogenesis is the biological production of methane mediated by anaerobic microorganisms from the domain Archaea commonly called methanogens. These methanogens are organism carrying out methanogenesis, requiring completely anaerobic conditions for growth. These methanogens are different from bacteria and eukarya as they lack peptidoglycan in their cell wall, which is present in bacteria and eukarya. Methane is produced by three major pathways on the basis of substrate utilized for methane production: (1) hydrogenotropic (2) acetoclastic and (3) methylotropic. Out of these, hydrogenotropic and acetoclastic is the predominant pathway. All three pathways have in common the demethylation of methyl–coenzyme M to methane and the reduction of the heterodisulfide of coenzyme M and coenzyme B catalysed by methyl–coenzyme M and heterodisulfide reductases. There are two major sources of methane i.e. natural and anthropogenic. The natural sources include wetlands, termites and oceans, whereas, the anthropogenic sources include fossil fuel transport and distribution, livestock, rice fields, landfills etc.