Microbial community dynamics of a sequentially fed anaerobic digester treating solid organic waste

Abstract

A 50 kg-scale, high solids anaerobic digestor (AD) comprising six sequentially-fed leach beds with a leachate recirculation system was operated at 37°C for 88 weeks. The solid feedstock contained a constant fibre fraction (a mix of cardboard, boxboard, newsprint, and fine paper) and varying proportions of food waste. Previously, we reported on the stable operation of this digestion system, where significantly enhanced methane production from the fibre fraction was observed as the proportion of food waste increased. The objective of this study was to identify relationships between process parameters and the microbial community. Increasing food waste led to a large increase in the absolute microbial abundance in the circulating leachate. While 16S rRNA amplicons for Clostridium butyricum were most abundant and correlated with the amount of FW in the system and with the overall methane yield, it was more cryptic Candidatus Roizmanbacteria and Spirochaetaceae that correlated specifically with enhanced methane from the fiber fraction. A faulty batch of bulking agent led to hydraulic channeling, which was reflected in the leachate microbial profiles matching that of the incoming food waste. The system performance and microbial community re-established rapidly after reverting to better bulking agent, illustrating the robustness of the system.

Metagenomes and metagenome-assembled genomes from a sequentially fed anaerobic digester treating solid organic municipal waste

“…Methane yield was greatly enhanced by the addition of food waste. The microbial community was monitored using 16S rRNA amplicon sequencing ( 2 ). Metagenomes from high solids digesters are rare compared to those from liquid, well-mixed anaerobic digesters.…”

“…We therefore selected four samples for metagenomic shotgun sequencing to get a blueprint of the functional potential of the community. The aim of this study was to obtain the genomes of organisms that emerged as key 16S rRNA gene amplicon sequence variants in correlative analyses ( 2 ).…”

“…Daisy was fed constant weekly additions of cardboard, boxboard, newsprint, fine paper, and wood chips, the latter as bulking agent ( 2 ). The amount of food waste (FW) fed weekly varied from 0 to 509 g FW as chemical oxygen demand (COD; measured using standard methods [ 3 ]), up to 29.3% FW on a COD basis.…”

“…DNA extractions were performed using the Qiagen DNeasy PowerSoil kit (Qiagen, Carlsbad, CA, USA) as described in detail by Lee et al ( 2 ). DNA from samples S62W2 and S80W1 were fragmented by Covaris (Covaris Inc., Woburn, MA, USA).…”