The relationship between instability of H₂ production and compositions of bacterial communities within a dark fermentation fluidised‐bed bioreactor

Abstract

Microbial community composition dynamics was studied during H(2) fermentation from glucose in a fluidized-bed bioreactor (FBR) aiming at obtaining insight into the H(2) fermentation microbiology and factors resulting in the instability of biofilm processes. FBR H(2) production performance was characterised by an instable pattern of prompt onset of H(2) production followed by rapid decrease. Gradual enrichment of organisms increased the diversity of FBR attached and suspended-growth phase bacterial communities during the operation. FBR bacteria included potential H(2) producers, H(2) consumers and neither H(2) producers nor consumers, and those distantly related to any known organisms. The prompt onset of H(2) production was due to rapid growth of Clostridium butyricum (99-100%) affiliated strains after starting continuous feed. The proportion trend of C. butyricum in FBR attached and suspended-growth phase communities coincided with H(2) and butyrate production. High glucose loading rate favoured the H(2) production by Escherichia coli (100%) affiliated strain. Decrease in H(2) production, associated with a shift from acetate-butyrate to acetate-propionate production, was due to changes in FBR attached and suspended-growth phase bacterial community compositions. During the shift, organisms, including potential propionate producers, were enriched in the communities while the proportion trend of C. butyricum decreased. We suggest that the instability of H(2) fermentation in biofilm reactors is due to enrichment and efficient adhesion of H(2) consumers on the carrier and, therefore, biofilm reactors may not favour mesophilic H(2) fermentation.

Performance and composition of bacterial communities in anaerobic fluidized bed reactors for hydrogen production: Effects of organic loading rate and alkalinity

“…The main fermentation products from glucose are not only H 2 , CO 2 , butyrate and acetate but also ethanol, lactate, formate, acetone and butanol [25]. The high efficiency of H 2 production in this bioreactor should be achieved in the bacterial composition presented as Clostridia dominant.…”

“…adjusting the buffer concentrations in the feed [25], and 10,000 and 30,000 mg L À1 with pH controlled constantly by automatic titration using sodium hydroxide and hydrochloric acid [11], and sucrose concentrations ranging from 5000 to 40,000 mg COD L À1 with pH buffer (5240 mg ammonium bicarbonate L À1 bicarbonate) [10].…”

Hydrogen Production and Performance of Anaerobic Fixed-Bed Reactors Using Three Support Arrangements From Cassava Starch Wastewater

“…Except by ethanol in R1 and R3 and lactic acid in R2 and R4, the increase in the concentration of acids and alcohols was proportional to the increase of OLR from 9.5 to 13.5 g.L -1 .d -1 (Table 3). Variations in the concentration of the metabolites suggest that the system presented changes among the fermentative pathways that were established in accordance with the operational conditions imposed to the reactor or even by the growth of different microbial communities (KOSKINEN et al, 2007;GUO et al, 2008).…”

Low‐temperature (9°C) AMD treatment in a sulfidogenic bioreactor dominated by a mesophilic Desulfomicrobium species

“…Sample analysis and calibration were performed according to the standard SFS-EN ISO 10304-2 (SFS, 1996). The presence of organic acids and alcohols (ethanol, butanol, acetate, propionate, butyrate, iso-butyrate, valerate, and caproate) was determined with a gas chromatograph as described by Koskinen et al (2006). DOC was determined with a TOC-5000 analyzer (Shimadzu).…”

“…DOC was determined with a TOC-5000 analyzer (Shimadzu). The analysis of the gas composition of the FBR gas phase and batch bottles was performed according to Koskinen et al (2006). Soluble iron in the influent was analyzed with an atomic absorption spectrometer (AAS, Perkin-Elmer, Waltham, MA, 1100B) according to standards SFS 3044 (1980a) andSFS 3047 (1980b).…”