The significance of microbial community functions and symbiosis in enhancing methane production during anaerobic digestion: a review

Abstract

The anaerobic digestion process used for methane production has been studied for decades but most studies focused on the optimisation of physico-chemical operating parameters. A holistic understanding of the role played by different microbial communities and their symbiotic associations in facilitating the breakdown of the organic substrates to form methane gas is very key and yet it has only received little attention. This review discusses the AD process and various traditional approaches that have been used to improve its efficiency. The major limitation of these approaches in failing to elucidate the actual roles played by the myriads of microorganisms within their communities and symbiotic associations, as a fundamental starting point for AD process control and optimisation was highlighted. A review of the AD microbial pathways so far known was done, followed by an introduction of the metagenomics coupled with metabolomics approach for a more intricate understanding of the biological processes that happen in AD systems. Progress in the application of this approach during the digestion of various organic substrates including animal manures was also reviewed and finally, prospects for the future use of multi-omics (metagenomics, transcriptomics and metabolomics) approach, were highlighted.