• Journal of Environmental Science International
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• v.5 no.3
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• pp.387-398
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• 1996

Granular sludge formation and it's activity change are the most important factors in achieving successful start-up and operation of UASB reactor. Nevertheless, the detailed mechanism is still unknown. On the basic of the experiments in laboratory-scale UASB reactor, the effect of hydrogen partial pressure on sludge granulation was evaluated. Size distribution method and specific metabolic activity of the sludge with the operation time were used as a means for estimating the degree of the sludge granulation. At the constant hydrogen loading, the granulation increased as starvation periods in hydrogen supply increased, resulting in high organic removal efficiency. It was evidient that hydrogen play very important role in granulation and sludge granulation was achieved through mutual symbiosis between hydrogen utilizing bacteria and hydrogen producing bacteria under the hydrogen dificient conditions. Key words : granular sludge, UASB reactor, hydrogen partial pressure.

• KSBB Journal
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• v.8 no.3
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• pp.243-255
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• 1993

In this study, it was observed that hydrogen Productivity varied with stirrer speed, bead radius, input glucose concentration and dilution rate in a continuous stirred tank reactor in which immobilized R. rubrum KS-301 was used as a hydrogen-producing bacterium The mass transfer resistance due to cell immobilization was also studied. In order to estimate an effectiveness factor, Des of glucose was first obtained, which was subsequently represented by the correlation equation between Dos and Xb, As a result external mass transfer resistance could be neglected for stirrer speeds greater than 400rpn With bead radius increasing, the hydrogen productivity and internal effectiveness factor decreased. With input 91ucose concentration increasing, the hydrogen productivity and interval and external effectiveness factor increased. Although an Internal effectiveness factor was not affected, hydrogen productivity Increased with dilution rate increasing. An overall effectiveness factor remained nearly constant for the dilution rates investigate4 but increased with input 91ucose concentration increasing.

• Journal of the Korea Organic Resources Recycling Association
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• v.19 no.2
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• pp.22-27
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• 2011

This study was performed to find out the optimum condition for hydrogen production by changing mixture ratio from 3:7(food waste water : swine wastewater) without pre-treatment of food wastewater and swine wastewater using a continuous reaction process. It was confirmed that hydrogen generation according to pH is the highest in a condition of pH 5.5, and that the optimum pH for hydrogen production in case of mixing food wastewater with swine wastewater is 5.5 through this. Hydrogen generation according to HRT showed high hydrogen generation rate in case of 4 days rather than 3 days, and this involves largely in vitality of hydrogen producing bacteria according to variation of the HRT value, so it is judged that HRT also acts as an important factor to hydrogen producing bacteria. The organic removal efficiency recorded a removal efficiency of maximum TS 52%, VS 71%, TSS 83% and VSS 89% at the 6th day of operation, and it was confirmed that organic removal efficiency is possible even through an hydrogen production process.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.6
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• pp.434-441
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• 2009

The effect of varying sulfate concentration on continuous fermentative hydrogen production was studied using enriched mixed microflora in continuously fed reactor. Glucose was used as a model substrate for carbohydrates, and hydraulic retention time (HRT) was maintained at 1, 0.5, 0.25 day, respectively. Sulfate concentration was 0${\sim}$20,000 mg/L and the operating pH was maintained at 5.5. The experimental results indicate that hydrogen production is not affected by high sulfate concentration and shorter HRT of 0.25 day enhance hydrogen production. At HRT 1, 0.5, 0.25 day, the hydrogen production rate and hydrogen yield were 2.6, 4.6, 9.4 L/day, and 2.0, 1.8, 1.6 mol $H_2$/mol glucose, respectively. Residual sulfate content was 96${\sim}$98, 95${\sim}$97, and 94${\sim}$97% at HRT 1, 0.5, 0.25 day which show that no sulfate reduction occurred in the reactor during the experiments. Results of Fluorescence In Situ Hybridization (FISH) may indicate the presence of HPB (hydrogen producing bacteria) under all experimental conditions. However, SRB (sulfate reducing bacteria) were not found.

• KSBB Journal
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• v.20 no.6
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• pp.464-469
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• 2005

For the biological production of hydrogen, a new fermentative hydrogen-producing bacterium, Enterobacter sp. SNU-1453, was isolated from a domestic landfill. During the culture of this bacterium, pH significantly decreased with the accumulation of various organic acids, and consequently this inhibited the production of hydrogen. It was found that the metabolic flux in this bacterium depended on the pH and affected the hydrogen production. A butanediol pathway was dominant during the fermentation when pH was not controlled. By controlling the pH at 7 this pathway can be shifted to a mixed acid pathway, which is favorable to the production of hydrogen.

• Journal of Hydrogen and New Energy
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• v.29 no.5
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• pp.427-433
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• 2018

This study was performed to evaluate initial pH and substrate concentration on hydrogen fermentation of protein. The optimum initial pH and substrate concentration of hydrogen fermentation using protein was 8.0 and 1.0 g peptone/L, respectively. The maximum hydrogen yield at initial pH 8.0 and 1.0 g peptone/L was $19.2{\pm}0.8mL\;H_2/g$ peptone. As results of VFAs analysis, percentages of valerate was similar to hydrogen yield. Also, C. stickalandii, which was hydrogen and valerate producing bacteria, was dominated.

• Korean Journal of Veterinary Research
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• v.55 no.3
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• pp.191-197
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• 2015

Escherichia (E.) coli is commensal bacteria found in the intestine; however, some pathogenic strains cause diseases in animals and humans. Although E. coli does not typically produce hydrogen sulfide ($H_2S$), $H_2S$-producing strains of E. coli have been identified worldwide. The relationship between virulence and $H_2S$ production has not yet been determined. Therefore, characteristics of $H_2S$-producing isolates obtained from swine feces were evaluated including antibiotic resistance patterns, virulence gene expression, and genetic relatedness. Rates of antibiotic resistance of the $H_2S$-producing E. coli varied according to antibiotic. Only the EAST1 gene was detected as a virulence gene in five $H_2S$-producing E. coli strains. Genes conferring $H_2S$ production were not transmissible although the sseA gene encoding 3-mercaptopyruvate sulfurtransferase was detected in all $H_2S$-producing E. coli strains. Sequences of the sseA gene motif CGSVTA around Cys238 were also identical in all $H_2S$- producing E. coli strains. Diverse genetic relatedness among the isolates was observed by pulsed-field gel electrophoresis analysis. These results suggested that $H_2S$-producing E. coli strains were not derived from a specific clone and $H_2S$ production in E. coli is not associated with virulence genes.

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.1
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• pp.54-57
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• 2003

H$_2$-producing bacteria were isolated from anaerobic granular sludge. Out of 72 colonies (36 grown under aerobic conditions and 36 under anaerobic conditions) arbitrarily chosen from the agar plate cultures of a Suspended sludge, 34 colonies (15 under aerobic conditions and 19 under anaerobic conditions) produced H2 under anaerobic conditions. Based on various biochemical tests and microscopic observations, they were classified into 13 groups and tentatively identified as follows: From aerobic isolates, Aeromonar spp. (7 strains), Pseudomonas spp. (3 strains), and Vibrio spp. (5 strains); from anaerobic isolates, Actinomyces spp. (11 Strains), Clostridium 5pp. (7 strains). and Porphyromonas sp. When glucose was used as the carbon substrate, all isolates showed a similar cell density and a H$_2$ production yield in the batch cultivations after 12 h (2.24-2.74 OD at 600 nm and 1.02-1.22 mol H$_2$/mol glucose, respectively). The major fermentation by-products were ethanol and acetate for the aerobic isolates, and ethanol, acetate and propionate for the anaerobic isolates. This study demonstrated that several H$_2$ producers in an anaerobic granular sludge exist En large proportions and their performance in terms of H$_2$ production is quite similar.

• Environmental Engineering Research
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• v.10 no.1
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• pp.7-14
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• 2005

The feasibility of hydrogen production with a raw seed sludge through direct acclimation of feedstock was investigated at acidogenic stage, and methane was harvested at followed methanogenic stage in an anaerobic two-stage process. Hydrogen content was higher than 57% at all tested organic loading rates (OLRs) and the yield of hydrogen ranged from 1.5 to 2.4 mol H2/mol hexose consumed and peaked at 6 gVSl-1day-1. Normal butyrate and acetate were main volatile fatty acids (VFAs), whereas the concentration of propionate was insignificant. The hydrogen-producing bacteria, Clostridium thermosaccharolyticum, was detected with strong intensity at all tested organic loading rates (OLRs) by denaturing gradient gel electrophoresis (DGGE) of the polymerase chain reaction (PCR) analysis. From COD balance in the process, the fraction of the feed-COD converted to the hydrogen-COD at acidogenic stage ranged from 7.9% to 9.3% and peaked at 6 gVSl-1day-1, whereas the fraction of feed-COD converted to the methane-COD at methanogenic stage ranged from 66.2% to 72.3% and peaked at 3 gVSl-1day-1.

• Microbiology and Biotechnology Letters
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• v.42 no.1
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• pp.41-50
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• 2014

In this study, the performances of PVA-encapsulation and non-encapsulation in a fed-batch bioreactor system were compared for biohydrogen production. Hydrogen production in the PVA-encapsulation bioreactor was not significantly different in comparison to the non-encapsulation bioreactor. However, the hydrogen gas in the encapsulation bioreactor could be stably produced when it was exposed to environmental difficulties such as pH impact by the accumulation of organic acids as fermentative metabolic products. Bacterial communities by DGGE analysis were differently shifted between the PVA-encapsulation and non-encapsulation bioreactors from the initial sludge. The community of hydrogen producing bacteria was stable during the experimental period in the PVA-encapsulation bioreactor compared to the non-encapsulation method. The absolute quantitation of the DNA copy number by a high-throughput droplet digital PCR system for six genera contributed to hydrogen production showing that the numbers of dominant bacteria existed at similar levels in the two bioreactors regardless of encapsulation. In both of two bioreactors, not only Clostridium and Enterobacter, which are known as anaerobic hydrogen producing bacteria, but also Firmicutes, Ruminococcus and Escherichia existed with $1{\times}10^5-1{\times}10^6$ copy numbers of ml-samples exhibiting rapid growth during the initial operation period.