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Candida parapsilosis 돌연변이주에 의한 Xylitol 생산조건의 최적화
오덕근,김상용,김정회,Oh, Deok-Kun,Kim, Sang-Yong,Kim, Jung-Hoe 한국응용생명화학회 1996 Applied Biological Chemistry (Appl Biol Chem) Vol.44 No.1
Candida parapsilosis ATCC 22019 돌연변이주를 이용하여 xylitol 생산에 영향을 주는 배양 조건인 pH와 온도 그리고 교반속도 및 산소전달속도등의 환경인자가 Xylitol의 생성에 미치는 영향을 살펴보았다. 발효조에서 pH가 증가 할수록 균체농도와 기질소비속도가 증가하여 발효시간이 단축되었다. 그러나, Xylitol생산은 pH 4.5와 5.5에서 큰 차이 없이 50g/l의 xylose로 부터 약 34g/l로 최대농도를 보여주었다. 온도가 증가 할수록 최대 비증식속도가 증가하였지만 최종 균체농도는 감소하였고, xylitol 생산성은 $30^{\circ}C$에서 최대값을 보여주었다. 산소전달속도의 영향을 조사하기 위하여 발효조의 교반속도를 변화시키면서 배양한 결과 균체농도는 산소 전달속도가 높을수록 증가하였지만, xylitol 생산은 크게 감소하였다. 교반속도를 150rpm(산소전달속도 $30\;hr^{-1}$에 해당)으로 배양할때 발효시간 62시간에서 50g/l의 xylose로 부터 xylitol 농도가 35.8g/l로 최대값을 나타내었다. Xylitol 생산성을 증가시키기 위하여 1차 발효가 끝난 발효조에서 균체를 회수하여 20g/l로 농축하여 최적조건인 pH 4.5, $30^{\circ}C$, 산소전달속도 $30\;hr^{-1}$에서 재배양을 하였을 때 50g/l의 xylose가 배양시간 약 18시간만에 모두 이용되었고 전환수율 80%에 해당하는 40g/l의 Xylitol이 생성되었다. 이때 Xylitol의 생산성은 2.22g/l-hr으로 일반 발효때 얻은 $0.5{\sim}g/l-hr$ 보다 약 $3{\sim}4$배 증가되었다. Effect of culture conditions such as pH, temperature, agitation speed and oxygen transfer rate on xylitol production from xylose by Candide parapsilosis ATCC 21019 mutant was investigated in a jar fermentor. The initial concentration of xylosr 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 $30^{\circ}C$. 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 $20{\sim}85\;hr{-1}\;of\;k_La$ (corresponding to $100{\sim}300$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 $0.58\;g/l{\sim}hr^{-1}$, 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, $30^{\circ}C$ 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 80ft on the basis of xylose consumption and volumetric productivity was $2.22\;g/l{\sim}hr$ which was increased by $3{\sim}4$ fold compared with $0.5{\sim}0.7\;g/l-hr$ obtained in a normal fermentation condition.
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.
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.