title: Microbial community structure of ethanol type fermentation in bio-hydrogen production.
abstract: Three continuous stirred-tank reactors (CSTRs) were used for H(2) production from molasses wastewater at influent pH of 6.0-6.5 (reactor A), 5.5-6.0 (reactor B), or 4.0-4.5 (reactor C). After operation for 28 days, the microbial community formed ethanol type (C), propionate type (A) and ethanol-butyrate-mixed type (B) fermentation. The H(2) production rate was the highest for ethanol type fermentation, 0.40 l (g VSS)(-1) day(-1) or 0.45 l H(2) (g COD removed)(-1). Microbial community dynamics and diversity were analysed using double-gradient denaturing gradient gel electrophoresis (DG-DGGE). Denaturing gradient gel electrophoresis profiles indicated that the community structures changed quickly in the first 14 days. Phylogenetic analysis indicated that the dominant bacterial groups were low G+C Gram-positive bacteria, Bacteroides, gamma-Proteobacteria and Actinobacteria; alpha-Proteobacteria, beta-Proteobacteria, delta-Proteobacteria and Spirochaetes were also presented as minor groups in the three reactors. H(2)-producing bacteria were affiliated with Ethanoligenens, Acetanaerobacterium, Clostridium, Megasphaera, Citrobacter and Bacteroides. An ethanol-based H(2)-producing bacterium, Ethanoligenens harbinense CGMCC1152, was isolated from reactor C and visualized using fluorescence in situ hybridization (FISH) to be 19% of the eubacteria in reactor C. In addition, isoenzyme activity staining for alcohol dehydrogenase (ADH) supported that the majority of ethanol-producing bacteria were affiliated with Ethanoligenens in the microbial community.
authors.affiliation: School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China.
authors.forename: Nanqi
authors.initials: N
authors.lastname: Ren
authors.forename: Defeng
authors.initials: D
authors.lastname: Xing
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Rittmann
authors.forename: Lihua
authors.initials: L
authors.lastname: Zhao
authors.forename: Tianhui
authors.initials: T
authors.lastname: Xie
authors.forename: Xin
authors.initials: X
authors.lastname: Zhao
mesh_terms: D001421:Bacteria, Anaerobic / Q000145:classification / Q000378:metabolism*; D019149:Bioreactors; D003246:Conservation of Energy Resources / Q000379:methods*; D016172:DNA Fingerprinting; D017753:Ecosystem; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D005525:Food-Processing Industry; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D017404:In Situ Hybridization, Fluorescence; D008965:Molasses / Q000382:microbiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000145:classification; D014865:Waste Disposal, Fluid / Q000379:methods; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D012336:RNA, Ribosomal, 16S; D014874:Water Pollutants, Chemical; D000431:Ethanol; D006859:Hydrogen