Microbial community structure in the main processes of anaerobic digestion of restaurant food waste

Abstract:

[Background] Anaerobic digestion is the main method for treating restaurant food waste in China. Microorganism plays a crucial role in the anaerobic fermentation of restaurant food waste, however, there is limited study on the microbial structure and biodiversity in this field. [Objective] This work is aiming at providing scientific evidences for improving restaurant food waste treatment technologies and bio-resource recycling efficiency, by analyzing the microbial diversity and community structure for each processing unit. [Methods] Three waste liquid samples from typical units of oil-water separation, anaerobic fermentation, and residue dewatering were collected in a typical restaurant food waste treatment plant. The high-throughput sequencing technology of 16S rRNA gene was applied to analyze the composition, abundance, dominant microorganism, and their impacting factors. [Results] The microbial communities in anaerobic fermentation and residue dewatering samples showed higher microbial diversity than those in oil-water separation samples. At the phylum level, Firmicutes accounted for the highest proportion of 81.1% in all samples, followed by Bacteroidetes and Chloroflexi, accounting for 15.81% and 4.59% respectively, and at the genus level, Lactobacillus, Syntrophomonas, etc. had higher relative abundance. Several generic microbes had both environmental and resource properties, e.g., Pseudomonas, which accounts for 32.67% relative abundance in residue dewatering process, had the function of producing polyhydroxyalkanoates (PHA) but contained few pathogenic or opportunistic pathogenic bacteria. The most significant impacting factor of microbial diversity was pH, followed by the ammonia nitrogen content. [Conclusion] Characteristics of microbial community structure and diversity in a typical restaurant food waste treatment plant were found in this work, in addition, several recommendations for optimizing the treatment process and promoting bio-resource recycling were put forward.