Microbial community in ethanol-methane coupling fermentation treating food waste

Abstract

The microbial communities in ethanol-methane coupling fermentation reactors were studied. The community structure variation was monitored at the genus and phylum levels using PowerSoil® DNA Isolation Kit with 16S ribosomal RNA (16S rRNA). The distribution of microbial communities in the ethanol reactor was higher than the methane reactor at the phylum and genus level, indicating the influence of coupling fermentation. Clostridia (hydrogen producer) was the dominant species throughout the process at genus and phylum levels. This result indicates the efficient degradation of organic acids. In addition, Archaea methanogen species (aceticlastic methanogens) utilize both acetate and hydrogen to produce methane. The dominance of Methanosaeta rather than Methanosarsina in the anaerobic digestion reactor (R1) of coupling fermentation added further valuable information on food waste treatment. Moreover, lactic acid bacteria species (Lactococcus) was dominant in the ethanol reactor (R2), suggesting the efficient conversion of food waste to lactic acid, which could continue its conversion to ethanol. Interestingly, the high amount of ammonia, salts, and volatile fatty acids (VFAs) (including high acetate) could promote the SAO pathway in the coupling fermentation system.