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Kazuhiro Takamizawa,Afroze Syeda Humayra,Yuki Hasegawa,Izumi Nomura,Young C. Chang,Takeshi Sato 한국생물공학회 2005 Biotechnology and Bioprocess Engineering Vol.10 No.1
Clostridium bifermentans strain DPH-1 has already been found to dechlorinate perchloroethylene (PCE) to cis-dichloroethylene (cis-DCE) via trichloroethylene (TCE). In this study, our investigation on different culture conditions of this DPH-1 strain was extended to find a more efficient and cost effective growth medium composition for this DPH-1 strain in bioremediation practices. Temperature dependency of strain DPH-1 showed that the growth starting time and PCE degradation at 15oC was very slow compared to that of 30oC, but complete PCE degradation occurred in both cases. For the proper utilization of strain DPH-1 in more cost effective bioremediation practices, a simpler composition of an effective media was studied. One component of the culture medium, yeast extract, had been substituted by molasses, which served as a good source of electron donor. The DPH-1 strain in the medium containing molasses, in the presence of K2HPO4 and KH2PO4, showed identical bacterial multiplication (0.135 mg protein mL-1h-1) and PCE degradation rates (0.38 M/h) to those of the yeast extract containing medium.
The Production of Xylitol by Enzymatic Hydrolysis of Agricultural Wastes
Kazuhiro Takamizawa,Lien Ha Tran,Masanori Yogo,Hiroshi Ojima,Keiichi Kawai,Tohru Suzuki,Osamu Idota 한국생물공학회 2004 Biotechnology and Bioprocess Engineering Vol.9 No.3
Agricultural waste products, beech wood and walnut shells, were hydrolyzed at 40oC using mixed crude enzymes produced by Penicillium sp. AHT-1 and Rhizomucor pusillus HHT-1. D-xylose, 4.1 g and 15.1 g was produced from the hydrolysis of 100 g of beech wood and walnut shells, respectively. For xylitol production, Candida tropicalis IFO0618 and the waste product hydrolyzed solutions were used. The effects on xylitol production, of adding glucose as a NADPH source, D-xylose and yeast extract, were examined. Finally, a 50% yield of xylitol was obtained by using the beech wood hydrolyzed solution with the addition of 1% yeast extract and 1% glucose at an initial concentration.
Kazuhiro Takamizawa,Eun-Sook Kim,Izumi Nomura,Yuki Hasegawa 한국생물공학회 2006 Biotechnology and Bioprocess Engineering Vol.11 No.6
A cis-1,2-dichloroethylene (cis-DCE)-degrading anaerobic bacterium, Clostridium sp. strain KYT-1, was isolated from a sediment sample collected from a landfill site in Nanji-do, Seoul, Korea. The KYT-1 strain is a gram-positive, endospore-forming, motile, rod-shaped anaerobic bacterium, of approximately 2.5~3.0 μm in length. The degradation of cis-DCE is closely related with the growth of the KYT-1 strain, and it was stopped when the growth of the KYT-1 strain became constant. Although the pathway of cis-DCE degradation by strain KYT-1 remains to be further elucidated, no accumulation of the harmful intermediate, vinyl chloride (VC), was observed during anaerobic cis-DCE degradation. Strain KYT-1 proved able to degrade a variety of volatile organic compounds, including VC, isomers of DCE (1,1-dichloroethylene, trans-1,2-dichloroethylene, and cis-DCE), trichloroethylene, tetrachloroethylene, 1,2-dichloroethane, 1,1,1-trichloroethane, and 1,1,2-trichloroethane. Strain KYT-1 degraded cis-DCE at a range of temperatures from 15 to 37℃, with an optimum at 30℃, and at a pH range of 5.5 to 8.5, with an optimum at 7.0.
Quantification of Bacillus Species in a Wastewater Treatment System by the Molecular Analyses
Kazuhiro Takamizawa,Koji Mori,Ryozo Iriye,Mutsunori Hirata 한국생물공학회 2004 Biotechnology and Bioprocess Engineering Vol.9 No.6
Bacillus species were observed and quantified by molecular approaches, using the 16S rDNA primers/probes, in a wastewater treatment plant designed for the purpose of stimulating the growth of Bacillus species. The plant has been operating as a test plant since 1997 in the city of Ina, Japan, with excellent treatment performance. Observations by in situ hybridization, using Bacillus-specific probes, indicated that Bacillus strains were inhabited in the plant and their numbers decreased during the treatment process. Similar results were obtained from a quantitative PCR analysis using a Bacillus-specific primer set, and the amount of DNA originating from various Bacillus species was maximally 1.91% of the total DNA in the wastewater treatment tank. Clone library analysis using the Bacillus-specific primers suggested that, while the population was noticeably increased, the phylogenetic diversity of the increasing Bacillus species was very low.
Characteristics of Dissimilatory Arsenate-reducing Bacteria
Young-Cheol Chang(장용철),Kazuhiro Takamizawa(다까미자와 카즈히로),Hoon Cho(조훈),Shintaro Kikuchi(키쿠치 신타로) 한국생물공학회 2012 KSBB Journal Vol.27 No.2
Although, microbial arsenic mobilization by dissimilatory arsenate-reducing bacteria (DARB) and the practical use to the removal technology of arsenic from contaminated soil are expected, most previous research mainly has been focused on the geochemical circulation of arsenic. Therefore, in this review we summarized the previously reported DARB to grasp the characteristic for bioremediation of arsenic. Evidence of microbial growth on arsenate is presented based on isolate analyses, after which a summary of the physiology of the following arsenaterespiring bacteria is provided: Chrysiogenes arsenatis strain BAL-1<SUP>T</SUP>, Sulfurospirillum barnesii, Desulfotomaculum strain Ben-RB, Desulfotomaculum auripigmentum strains OREX-4, GFAJ-1, Bacillus sp., Desulfitobacterium hafniense DCB-2<SUP>T</SUP>, strain SES-3, Citrobacter sp. (TSA-1 and NC-1), Sulfurospirillum arsenophilum sp. nov., Shewanella sp., Chrysiogenes arsenatis BAL-l<SUP>T</SUP>, Deferribacter desulfuricans. Among the DARB, Citrobacter sp. NC-1 is superior to other dissimilatory arsenate-reducing bacteria with respect to arsenate reduction, particularly at high concentrations as high as 60 mM. A gram-negative anaerobic bacterium, Citrobacter sp. NC-1, which was isolated from arsenic contaminated soil, can grow on glucose as an electron donor and arsenate as an electron acceptor. Strain NC-1 rapidly reduced arsenate at 5 mM to arsenite with concomitant cell growth, indicating that arsenate can act as the terminal electron acceptor for anaerobic respiration (dissimilatory arsenate reduction). To characterize the reductase systems in strain NC-1, arsenate and nitrate reduction activities were investigated with washed-cell suspensions and crude cell extracts from cells grown on arsenate or nitrate. These reductase activities were induced individually by the two electron acceptors. Tungstate, which is a typical inhibitory antagonist of molybdenum containing dissimilatory reductases, strongly inhibited the reduction of arsenate and nitrate in anaerobic growth cultures. These results suggest that strain NC-1 catalyzes the reduction of arsenate and nitrate by distinct terminal reductases containing a molybdenum cofactor. This may be advantageous during bioremediation processes where both contaminants are present. Moreover, a brief explanation of arsenic extraction from a model soil artificially contaminated with As (V) using a novel DARB (Citrobacter sp. NC-1) is given in this article. We conclude with a discussion of the importance of microbial arsenate reduction in the environment. The successful application and use of DARB should facilitate the effective bioremediation of arsenic contaminated sites.