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Candida parapsilosis 돌연변이주에 의한 Xylitol 생산의 배지조건 최적화
오덕근,윤상현,김정민,김상용,김정회 한국미생물생명공학회 ( 구 한국산업미생물학회 ) 1996 한국미생물·생명공학회지 Vol.24 No.4
Candida parapsilosis ATCC 22019 돌연변이주를 사용하여 xylitol 생산에 영향을 주는 배지성분의 최적화를 수행하였다. Xylose 50 g/l 배지에서 여러 가지 질소원이 xylitol 생산에 미치는 영향을 살펴본 결과 xylitol 생산에는 무기질소원으로는 (NH_4)_2SO_4가 좋았으며 유기질소원으로는 yeast extract가 가장 좋았다. 무기염으로 KH_2PO_4 ad MgSO_4·7H_2O를 선정하여 최적화를 수행하였고 그 결과 최적배지로 xylose of 50 g/l, yeast extract of 5 g/l, (NH_4)_2SO_4 of 5 g/l, KH_2PO_4 of 5 g/l, MgSO_4·7H_2O of 0.2 g/l로 결정하였다. 최적배지를 사용하여 발효조에서 64시간 배양하였을 때 xylose는 모두 소모되었으며 최종 균체농도와 xylitol 생산량은 각각 7.6 g/l와 37 g/l을 얻었다. 이때, xylose로 부터 xylitol의 전환수율 74%이었고, xylitol의 생산성은 0.58 g/l-hr이었다. 최적배지에서 총 첨가된 xylose에 대한 xylitol의 생산수율 80.7%에 해당되었고 xylitol의 생산성은 0.94g/l-hr에 해당되었다. Medium optimization for xylitol production from xylose by Candida parapsilosis ATCC 22019 mutant was performed. Effect of various nitrogen sources on xylitol production was investigatied. Of inorganic nitrogenous compounds, ammonium sulfate was effective for xylitol production and yeast extract was the most suitable orangic nitrogen nutrient for enhancement of xylitol production. Effect of inorganic salts such as KH_2PO_4 ad MgSO_4·7H_2O on xylitol production was also studied. Optimal medium was selected as xylose of 50 g/l, yeast extract of 5 g/l, (NH_4)_2SO_4 of 5 g/l, KH_2PO_4 of 5 g/l, MgSO_4·7H_2O of 0.2 g/l. In a fermentor by using the optimal medium, a final xylitol concentration of 37 g/l could be obtained from 50 g/l of xylose with a xylitol yield of 74% and a xylitol productivity of 0.58 g/l-hr. At 300 g/l xylose, fermentation was also carried out and then a final xylitol concentration of 242 g/l was obtained at 272 hours. It was corresponding to xylitol yield of 80.7% and xylitol productivity of 0.58 g/l-hr.
Mercury Adsorption of Chemically Modified Polysaccharide from Methylobacterium organophilum
Oh, Deok Kun,Kim, Jung Hoe,Kim, Sang Yong,Lee, Jung Gul 한국농화학회 1998 Applied Biological Chemistry (Appl Biol Chem) Vol.41 No.4
Methylan, a polysaccharide produced from Methylobacterium organophilum, was chemically modified by adding diethylaminoethyl (DEAE) group to the backbone of methylan. The structure of DEAE-methylan was determined by measuring its nitrogen content obtained from an elemental analysis. From the analysis of mass spectrum, the DEAE group in DEAE-methylan was also confirmed by determining diethylaminoethene as a separate form of DEAE. Mercury adsorption of DEAE-methylan was higher than that of native methylan. This fact was valid for a variety of pH, reaction times, metal concentrations, and polysaccharide concentrations. In particular, native methylan and DEAE-methylan adsorbed 16% (w/w) and 18% (w/w) for mercury after 30 min at pH 7, respectively. The increase in mercury adsorption of DEAE-methylan may be resulted from mercury adsorption by the lone pair electron of nitrogen atom in DEAE group.
다당류 , 메틸란 , 발효배양액의 점성특성과 메틸란 생산에 미치는 교반속도의 영향
오덕근(Deok Kun Oh),임현수(Hyun Soo Lim),김정회(Jung Hoe Kim) 한국응용생명화학회 1995 Applied Biological Chemistry (Appl Biol Chem) Vol.38 No.3
Production of a high viscosity exoploysaccharide, methylan, by Methylobacterium organophilum from methanol was carried out in fed-batch cultures and the rheological properties of methylan fermentation broth were studied. Bacterial biomass showed little influence on viscosity, but the accumulation of methylan caused the increase of viscosity. With proceeding fermention, the viscosity at the same concentration of methylan was significantly increased and methylan solution showed slightly higher pseudoplasticity. The composition changes of methylan were investigated at various fermentation times. Contents of total sugar, reducing sugar and methylan were decreased but contents of acids(pyruvic acid, uronic acid and acetic acid) were increased with the culture time. It was considered that the increased content of acids resulted in the increase of the hyrodynamic domain in the solution due to charge repulsion. Consequently, the solution viscosity increased in propotion to the acids contents of methylan. Cell growth and methylan production were severely decreased by the limitation of dissolved oxygen. However, the cellular activity for methylan production was almost constant regardless of the level of dissolved oxygen. As a result, the high speed of agitation increased the methylan production, the specific production rate of methylan, and the methylan yield of the cell.
Candida parapsilosis 돌연변이주에 의한 Xylitol 생산조건이 최적화
오덕근(Deok Kun Oh),김상용(Sang Yong Kim),김정회(Jung Hoe Kim) 한국응용생명화학회 1996 Applied Biological Chemistry (Appl Biol Chem) Vol.39 No.3
Effect of culture conditions such as pH. temperature, agitation speed and oxygen transfer rate on xylitol production from xylose by Candida parapsilosis ATCC 21019 mutant was investigated in a jar fermentor. The initial concentration of xylose was fixed at 50 g/ℓ in this experiment. When pH was increased, cell growth and xylose consumption rate were increased, but maximum xylitol production was shown in the range of pH 4.5 and 5.5 with a yield of 0.68 g/g-xylose. The optimal temperature for xylitol production was determined to be 30℃. Considering the importance of dissolved oxygen tension, for xylitol production, the effect of oxygen transfer rate coefficient (k_La) on fermentation parameters was carefully evaluated in the range of 20∼85 hr^(-1) of k_La (corresponding to 100∼300 rpm of agitation speed). The xylitol production was maximized at 30 hr^(-1) of k_La (150 rpm). A higher oxygen transfer rate supported better cell growth with lower xylitol yield. It was determined that maximum xylitol concentration, xylitol yield and productivity was 35.8 g/ℓ, 71.6% and 0.58 g/ℓ∼hr, respectively, at 30 hr^(-1) of k_La. In order to further increase xylitol productivity, ferementation using the concentrated biomass(20 g/ℓ) was carried out at the conditions of pH 4.5, 30℃ and 30 hr^(-1) of oxygen transfer rate. The final xylitol concentration of 40 g/ℓ was obtained at 18 hours of culture time. From this result, it was calculated that xylitol yield was 80% on the basis of xylose consumption and volumetric productivity was 2.22 g/ℓ∼hr which was increased by 3∼4 fold compared with 0.5∼0.7 g/ℓ-hr obtained in a normal fermentation condition.