title: Fermentative hydrogen production and bacterial community structure in high-rate anaerobic bioreactors containing silicone-immobilized and self-flocculated sludge.
abstract: A novel continuously stirred anaerobic bioreactor (CSABR) seeded with silicone-immobilized sludge was developed for high-rate fermentative H2 production using sucrose as the limiting substrate. The CSABR system was operated at a hydraulic retention time (HRT) of 0.5-6 h and an influent sucrose concentration of 10-40 g COD/L. With a high feeding sucrose concentration (i.e., 30-40 g COD/L) and a short HRT (0.5 h), the CSABR reactor produced H2 more efficiently with the highest volumetric rate (VH2) of 15 L/h/L (i.e., 14.7 mol/d/L) and an optimal yield of ca. 3.5 mol H2/mol sucrose. The maximum VH2 value obtained from this work is much higher than any other VH2 values ever documented. Formation of self-flocculated granular sludge occurred during operation at a short HRT. The granule formation is thought to play a pivotal role in the dramatic enhancement of H2 production rate, because it led to more efficient biomass retention. A high biomass concentration of up to 35.4 g VSS/L was achieved even though the reactor was operated at an extremely low HRT (i.e., 0.5 h). In addition to gaining high biomass concentrations, formation of granular sludge also triggered a transition in bacterial community structure, resulting in a nearly twofold increase in the specific H2 production rate. According to denatured-gradient-gel-electrophoresis analysis, operations at a progressively decreasing HRT resulted in a decrease in bacterial population diversity. The culture with the best H2 production performance (at HRT = 0.5 h and sucrose concentration = 30 g COD/L) was eventually dominated by a presumably excellent H2-producing bacterial species identified as Clostridium pasteurianum.
authors.affiliation: Department of Chemical Engineering, Feng Chia University, Taichung, Taiwan.
authors.forename: Shu-Yii
authors.initials: SY
authors.lastname: Wu
authors.forename: Chun-Hsiung
authors.initials: CH
authors.lastname: Hung
authors.forename: Chi-Neng
authors.initials: CN
authors.lastname: Lin
authors.forename: Hsin-Wei
authors.initials: HW
authors.lastname: Chen
authors.forename: An-Sheng
authors.initials: AS
authors.lastname: Lee
authors.forename: Jo-Shu
authors.initials: JS
authors.lastname: Chang
mesh_terms: D019342:Acetic Acid / Q000378:metabolism; D001421:Bacteria, Anaerobic / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology*; D020148:Butyric Acid / Q000378:metabolism; D018914:Cells, Immobilized / Q000378:metabolism* / Q000648:ultrastructure; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D004275:DNA, Ribosomal / Q000032:analysis / Q000235:genetics; D005285:Fermentation; D006859:Hydrogen / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012722:Sewage / Q000737:chemistry / Q000382:microbiology*; D020034:Silicone Gels / Q000737:chemistry; D013045:Species Specificity; D013395:Sucrose / Q000378:metabolism
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D012722:Sewage; D020034:Silicone Gels; D020148:Butyric Acid; D013395:Sucrose; D006859:Hydrogen; D019342:Acetic Acid