Simulating Rumen Conditions using an Anaerobic Dynamic Membrane Bioreactor to Enhance Hydrolysis of Lignocellulosic Biomass

Abstract

An anaerobic dynamic membrane bioreactor (AnDMBR) was used to mimic rumen conditions to enhance the hydrolysis of lignocellulosic materials and the production of volatile fatty acids (VFA) when treating food waste. The AnDMBR was inoculated with cow rumen content and operated at a 0.5-day hydraulic retention time, 2 to 4-day solids retention time, a temperature of 39 {degrees}C, and a pH of 6.3, characteristics similar to those of a rumen. An operational strategy of repeating settle-permeate-mix cycles was utilized to simulate the regurgitation of ruminant animals. Removal rates of neutral detergent fiber (NDF) and acid detergent fiber (ADF) of 58.9 {+/-} 8.4 % and 69.0 {+/-} 8.6 %, respectively, and a VFA yield of 0.55 {+/-} 0.12 g VFA/g CODfed were observed when operating at an organic loading rate of 18 {+/-} 2 kg VS/m3/day. Sequencing results of both 16S rRNA gene and 16S rRNA revealed that a microbial community resistant to both disruption and reinoculation developed six weeks after inoculation. Up to 66.7 {+/-} 5.7 % of the active microbial populations (based on 16S rRNA sequence data) and 51.0 {+/-} 7.0 % of the total microbial populations (based on 16S rRNA gene sequence data) present in the rumen-mimicking AnDMBR originated from the rumen inoculum. This study offers a reliable strategy to leverage the unique features of a rumen; the rumen-mimicking AnDMBR achieved high hydrolysis and acidogenesis rates even when treating substrates drastically different from those fed to ruminants.