Microbial community analysis in a combined anaerobic and aerobic digestion system for treatment of cellulosic ethanol production wastewater

Abstract

This study investigated the microbial diversity established in a combined system composed of a continuous stirred tank reactor (CSTR), expanded granular sludge bed (EGSB) reactor, and sequencing batch reactor (SBR) for treat ment of cellulosic ethanol production wastewater. Excellent wastewater treatment performance was obtained in the com bined system, which showed a high chemical oxygen demand removal efficiency of 95.8 % and completely eliminated most complex organics revealed by gas chromatography–mass spectrometry (GC–MS). Denaturing gradient gel electropho resis (DGGE) analysis revealed differences in the microbial community structures of the three reactors. Further identifica tion of the microbial populations suggested that the presence of Lactobacillus and Prevotella in CSTR played an active role in the production of volatile fatty acids (VFAs). The most diverse microorganisms with analogous distribution patterns of different layers were observed in the EGSB reactor, and bacteria affiliated with Firmicutes, Synergistetes, and Thermotogae were associated with production of acetate and carbon dioxide/hydrogen, while all acetoclastic methanogens identified belonged to Methanosaetaceae. Overall, microor ganisms associated with the ability to degrade cellulose, hemicellulose, and other biomass-derived organic carbons were observed in the combined system. The results presented herein will facilitate the development of an improved cellulos ic ethanol production wastewater treatment system.