• Journal of Microbiology and Biotechnology
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• 제20권3호
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• pp.615-621
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• 2010

The viability of low-temperature sulfate reduction with hydrogen as electron donor was studied with a bench-scale gas-lift bioreactor (GLB) operated at $9^{\circ}C$. Prior to the GLB experiment, the temperature range of sulfate reduction of the inoculum was assayed. The results of the temperature gradient assay indicated that the inoculum was a psychrotolerant mesophilic enrichment culture that had an optimal temperature for sulfate reduction of $31^{\circ}C$, and minimum and maximum temperatures of $7^{\circ}C$ and $41^{\circ}C$, respectively. In the GLB experiment at $9^{\circ}C$, a sulfate reduction rate of 500-600 mg $l^{-1}d^{-1}$, corresponding to a specific activity of 173 mg ${SO_4}^{2-}g\;VSS^{-1}d^{-1}$, was obtained. The electron flow from the consumed $H_2$-gas to sulfate reduction varied between 27% and 52%, whereas the electron flow to acetate production decreased steadily from 15% to 5%. No methane was produced. Acetate was produced from $CO_2$ and $H_2$ by homoacetogenic bacteria. Acetate supported the growth of some heterotrophic sulfate-reducing bacteria. The sulfate reduction rate in the GLB was limited by the slow biomass growth rate at $9^{\circ}C$ and low biomass retention in the reactor. Nevertheless, this study demonstrated the potential sulfate reduction rate of psychrotolerant sulfate-reducing mesophiles at suboptimal temperature.

• KSBB Journal
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• 제20권6호
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• pp.408-412
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• 2005

Headspace의 이산화탄소 제거는 수소의 수율을 올릴 수 있는 효과적인 방법이지만, 증가된 수소의 분압(최대 91.2%)과 이산화탄소의 부재에 의해 글루코즈의 발효 경향에 상당한 영향을 미치는 것으로 나타났다. 이산화탄소의 제거는 homoacetogenesis에 의한 수소의 소모를 효과적으로 억제하였지만, 주요발효 부산물인 ethanol 및 기타 발효 부산물의 분해 또한 억제하는 결과를 나타내었다. 또한 소량으로 발생한 부산물들의 분석결과에서 이산화탄소가 제거된 반응에서 반응 후반부에 butyrate의 증가하는 현상이 관찰되었다. 하지만, 기존의 연구결과들처럼 증가된 수소의 분압에 의한 과다한 solvent의 생성은 관찰되지 않았으며, acetate의 과도한 발생을 방지할 수 있어 acetate에 의한 저해현상을 다소 억제할 수 있을 것으로 사료된다. 이산화탄소가 제거될 경우 최종 산물이 수소와 ethanol이므로 목적 반응이 hydrogen-ethanol fermentation이라면 이상적인 방향을 제시할 수 있을 것이다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제17권5호
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• pp.49-55
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• 2012

A 1.28 L-batch reactor and continuous-flow stirred tank reactor (CFSTR) fed with formate and trichloroethene (TCE) were operated for 120 days and 56 days, respectively, to study the effect of formate as electron donor on anaerobic reductive dechlorination (ARD) of TCE to cis-1,2-dichloroethylene (c-DCE), vinyl chloride (VC), and ethylene (ETH). In batch reactor, injected 60 ${\mu}mol$ TCE was completely degraded in the presence of 20% hydrogen gas ($H_2$) in less than 8 days by anaerobic dechlorination mixed-culture (300 mg-soluble protein), Evanite Culture with ability to completely degrade tetrachloroethene (PCE) and -TCE to ETH under anaerobic conditions. Once the formate was used as electron donor instead of hydrogen gas in batch or chemostat system, the TCE-dechlorination rate decreased and acetate production rate increased. It indicates that the concentration of hydrogen produced in both systems is possibly more close to threshold for homoacetogenesis process. Soluble protein concentration of Evanite culture during the batch test increased from 300 mg to 688 mg for 120 days. Through the protein monitoring, we confirmed an increase of microbial population during the reactor operation. In CFSTR test, TCE was fed continuously at 9.9 ppm (75.38 ${\mu}mol/L$) and the influent formate feed concentration increased stepwise from 1.3 mmol/L to 14.3 mmol/L. Injected TCE was accumulated at 18 days of HRT, but TCE was completely degraded at 36 days of HRT without accumulation of the injected-TCE during the left of experiment period, getting $H_2$ from fermentative hydrogen production of injected formate. Although c-DCE was also accumulated for 23 days after beginning of CFSTR operation, it reached steady-state in the presence of excessive formate. We also evaluated microbial dynamic of the culture at different chemical state in the reactor by DGGE (denaturing gradient gel electrophoresis).