Fats, oils, and grease (FOG) are energy-dense waste that substantially increases biomethane recovery via their conversion through long-chain fatty acids (LCFAs). During the anaerobic codigestion of high amount of FOG (5% v/v), we assessed the microbial community shifts at different taxonomic levels in order to understand the relations between substrate digestion and microbial adaptations, and their link to reactor performance. The excessive addition of FOG inhibited the methanogenic activity during the initial phase of the experimental duration (until 32 d); however, the methanogens recovered from the earlier inhibition caused due to adsorption of LCFAs on the cell surfaces. The addition of FOG enhanced the cumulative methane production by 2775% compared to the control (without FOG). The metagenomic analysis was conducted at regular interval of anaerobic codigestion. The phylum level analysis showed that, Proteobacteria were dominating (43%) before the addition of FOG; whereas, the dominance of Proteobacteria was decreased with simultaneous increase of Firmicutes, Bacteriodates, Synergistetes and Euryarchaeota during the digestion of FOG. Among 40 dominant genera, the species assigned to Syntrophomonas genus were increased to ~12% during codigestion, which substantiates the importance of Syntrophomonas species in LCFA degradation in anaerobic co-digestion. Interestingly, the abundance studies of genera related to methanogenic communities indicated that, the dominance of methanosaeta population at the beginning of the co-digestion was significantly taken over by the population of methanosarcina at the end of digestion. It indicates that the methane production is linked with high relative activity and abundance of syntrophic fatty acid oxidizers alongside the acetoclastic and hydrogenotrophic methanogens, signaling the importance of interspecies interactions in anaerobic co-digestion. Overall, these results suggest that syntrophic populations in anaerobic co-digestion have different adaptive capacities, and that selection for divergent populations may be achieved by adjusting the operating conditions of reactor to maximize biomethane recovery.

Dissecting microbial community shifts during anaerobic co-digestion of fat, oil and grease (FOG)

256th National Meeting (2018)

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