Unraveling the microbial interactions in coal organic fermentation for generation of methane — A classical to metagenomic approach

Abstract

Coal bed methane (CBM) obtained in the deep unmined coal reserves stands as a promising alternative source of energy for the diversified energy needs. Biogenic methane can consist of the significant portion of the gas from the coal beds as a result of microbial activity on the coal. The growing interest of enhancing the CBM production led to obtain the detailed information of the microbes and the development of a suitable microbial consortium capable of biotransforming coal to methane from the coal dust and the selectively enriched sump sediment water of the underground coal mines of the Jharia basin in the present study for the first time. The change of zeta potential from −40.6 to −8.3mV indicated the probable modification of coal structure by the microbes. The collected subbituminous pure coal revealed a decrease in carbon content from 60.33% to 54.22% when inoculated with the enriched sump sediment water. The growth studies indicated significant microbial growth in the medium with C:N ratio (100:25), under anaerobic conditions. An increased methane production of 2.7 times was observed from the enriched sump sediment water as compared to coal dust inoculum. The prevalence of Firmicutes, Proteobacteria and the hydrogenotrophic methanogens was obtained in the coal dust and enriched sump sediment metagenomes via MG RAST server. The functional attributes obtained through SEED subsystem revealed the predominance of the monoaromatic and aliphatic compound degradation in both the metagenomes. This study aims to develop a microbial consortium through selective enrichment followed by the media amendment with the pre-digested organic nitrogen source for an enhanced coal biomethanation which can be applied to the unexplored and unmined coal seams of medium to low grade as an alternative form of energy.