Dark Fermentative Hydrogen Production from Xylose in Different Bioreactors Using Sewage Sludge Microflora

Abstract

In this study, the H2-producing activity of the sewage sludge microflora using xylose as the sole carbon substrate was investigated in three bioreactor systems, including a suspended continuously stirred tank reactor (CSTR), an immobilized-cell continuously stirred anaerobic bioreactor (IC-CSABR), and a powder activated carbon-assisted agitated granular sludge bed (AGSB). For suspended-culture CSTR operations, fermentative H2 production was conducted at different hydraulic retention times (HRT = 4–12 h). The H2 production rate (HPR) was 183 mmol/L/d at HRT = 12 h, but the H2 production rate and yield decreased significantly when the HRT was shortened to 4 h due primarily to the washout of cells. To improve the operational stability of short HRTs, silicone-immobilized cells (IC-CSABR system) and powder activated carbon carriers (AGSB system) were adopted for the reactor systems to either maintain stable biomass concentration in the reactor or enhance biomass content by stimulating sludge granulation. Both IC-CSABR and AGSB showed improved biomass retention while operating at a HRT of 4 h. In particular, the biomass content in the IC-CSABR system (HRT = 2 h) went up to 8.03 g of VSS/L, leading to a drastic enhancement in the H2 production rate (1.06 mol/L/d). Bacterial community analysis by denatured gradient gel electrophoresis (DGGE) indicates a transition in bacterial composition in the CSTR under different HRT conditions. Moreover, under the same HRT (4 h), the major bacterial populations in the AGSB and IC-CSABR reactors were very different from those observed in the CSTR, indicating that the performance of H2 production seemed to be in close connection with the bacterial community structure. Several H2-producing bacterial strains (e.g., Clostridium butyricum and Klebsiella pneumoniae) were also detected in the sludge samples by DGGE and 16S rDNA sequence matching, revealing the effectiveness of the H2-producing sludge used in this study.

Effect of fermentation temperature on hydrogen production from xylose and the succession of hydrogen‐producing microflora

“…Hydrogen production performance was directly affected by the liquid metabolites distribution. The theoretical maximum hydrogen yield of 3.33 and 1.67 mol‐xylose could be achieved when only acetate and butyrate are produced as liquid product, respectively . When sugar is metabolized through propionate, hydrogen is consumed .…”

“…Based on our previous study, xylose solution of 30.0 g L −1 was used as carbon source . Sufficient inorganics (mg L −1 ) were prepared in the substrate to provide the essential nutrients and trace elements for H 2 ‐producing consortia: 382.1 NH 4 Cl, 87.7 KH 2 PO 4 , 260.0 CaCl 2 · 2H 2 O, 320.0 MgSO 4 · 7H 2 O, 125.0 FeSO 4 · 7H 2 O, 0.3397 Zn 2+ , 0.3365 Ni 2+ , 1.5747 Co 2+ , 0.2661 B 3+ , 2.8646 Mn 2+ , 5.7380 I − , 0.1920 Cu 2+ , 0.5950 Mo 6+ …”

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

“…Facultative anaerobes (such as Enterobacter and Klebsiella) are efficient in producing H 2 compared to strict anaerobes (such as Clostridium). H 2 production at partially anaerobic conditions is technically feasible for facultative anaerobes [50,51].…”

“…Yokoi et al [53] (5,12,15,24,28,33,53,55,65,68,70,78,84,88,90,92,96,102,104,114,115) Flavobacteria Clostridium butyricum (AB595129. 1) clones (11,22,27,29,34,50,79,82,105,116,117,118) Clostridium magnum (GU129927.1) Clostridium sp. (AF281142.1) Uncultured Veillonellaceae (FJ393139.1) Uncultured Veillonellaceae (FJ393127.1) clones (6,13,17,19,32,36,37,39,47,49,56,59,67,71,74,80,85,93,94,99,100,106,…”

Application of Pretreatment, Bioaugmentation and Biostimulation for Fermentative Hydrogen Production from Maize Silage

“…Enriching H 2 -producing pure and mixed microbial cultures from anaerobic substrates, mostly sludge are described in several studies [12][13][14]. Usually microbial cultures are used for biodegradation experiments with defined and relatively simple model substrates, for example starch [15], xylose [16] or sewage sludge [8]. Nevertheless, microbiologists are still seeking ideal cultures.…”