H2-Producing bacterial communities from a heat-treated soil inoculum

Abstract

Hydrogen gas (approximately 60% H(2)) was produced in a continuous flow bioreactor inoculated with heat-treated soil, and fed synthetic wastewater containing glucose (9.5 g l(-1)). The pH in the bioreactor was maintained at 5.5 to inhibit consumption of H(2) by methanogens. The objective of this study was to characterize bacterial communities in the reactor operated under two different hydraulic retention times (HRTs of 30-h and 10-h) and temperatures (30 degrees C and 37 degrees C). At 30-h HRT, the H(2) production rate was 80 ml h(-1) and yield was 0.91 mol H(2)/mol glucose. At 10-h HRT, the H(2) production rate was more than 5 times higher at 436 ml h(-1), and yield was 1.61 mol H(2)/mol glucose. Samples were removed from the reactor under steady-state conditions for PCR-based detection of bacterial populations by ribosomal intergenic spacer analysis (RISA). Populations detected at 30-h HRT were more diverse than at 10-h HRT and included representatives of Bacillaceae, Clostridiaceae, and Enterobacteriaceae. At 10-h HRT, only Clostridiaceae were detected. When the temperature of the 10-h HRT reactor was increased from 30 degrees C to 37 degrees C, the steady-state H(2) production rate increased slightly to 463 ml h(-1) and yield was 1.8 mol H(2)/mol glucose. Compared to 30 degrees C, RISA fingerprints at 37 degrees C from the 10-h HRT bioreactor exhibited a clear shift from populations related to Clostridium acidisoli (subcluster Ic) to populations related to Clostridium acetobutylicum (subcluster Ib).

Fermentative hydrogen production in packed-bed and packing-free upflow reactors

“…are fermentative hydrogen-producers (Solomon et al, 1995;Tseng, 2004). A clone closely related to Klebsiella ornithinolytica (similarity 98%) has been found in a hydrogen-producing sludge previously (Iyer et al, 2004). The OTUs G-HPB-42 and -85 were distantly related to Clostridium cellulosi with similarities of 94% and 95%, respectively.…”

Genetic Diversity of Hydrogen-Producing Bacteria in an Acidophilic Ethanol-H2-Coproducing System, Analyzed Using the [Fe]-Hydrogenase Gene

“…This finding was consistent with previous investigations (37,38), in which a pH of 4.0 to 4.5 led to ethanol-H 2 coproduction in an unbuffered system. The H 2 yields were about 0.13 and 0.15 g of OD in H 2 ⅐ g Ϫ1 of OD in glucose (1.6 and 1.8 mol of H 2 ⅐ mol Ϫ1 of glucose) in the two reactors, values typical of H 2 yields found in fermentative H 2 production from food waste, glucose, and cellulose as substrates at a pH of Ͼ5 or 5.5 (23,43,46). However, a simple comparison is unreasonable, due to differences in inocula, substrates, and operation conditions.…”

“…Previous investigations (2,15,23,43,46) indicated that the dominant populations from hydrogen-producing sludge were Clostridium, Bacillus, and Staphylococcus groups of low-GϩC-content gram-positive bacteria; putative HPB were affiliated with Clostridium, Thermoanaerobacterium, Desulfotomaculum, and Thermotogales spp. In contrast, the majority of the dominant populations based on hydA were affiliated with low-GϩC-content gram-positive bacteria, Bacteroidetes, and Actinobacteria groups.…”

Optimization of Operational Parameters for Biohydrogen Production from Waste Sugarcane Leaves and Semi-Pilot Scale Process Assessment

“…and Enterobacter sp. The presence of species belonging to the Enterobacter and Klebsiella genii after heat treatment at 105 °C for 2 h was also observed in a study by Iyer et al (2004). Because of their rapid growth rate and efficient substrate consumption, facultative anaerobes often dominate microbial communities during fermentation, thus outcompeting other microbial species (Zhang et al 2015).…”