• KSBB Journal
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• 제4권2호
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• pp.74-77
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• 1989

Volumetric productivity를 향상시키기 위하여 미생물 재순환에 의한 연속 시스템을 이용하였다. 연속발효조의 연구에서 9.2g/1와 15.0,g/1의 범위의 세포 농도를 유지할 수 있었다. 4%의 xylose의 feed와 1.04g $O{_2}$hr-g DCW의 specific oxygen supply rate의 조건에서 희석율이 0.0349 h$^{-1}$ethanol 수율은 0.36이었다. Ethanol volumetric productivity는 같은 희석율에서 0.244g/hr-$\ell$로 증가하였으며 이것은 회분배양값의 260%이었다.

• Journal of Microbiology and Biotechnology
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• 제24권2호
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• pp.264-269
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• 2014

For the production of ethanol from seaweed as the source material, thermal acid hydrolysis and enzymatic saccharification were carried out for monosugars production of 25.5 g/l galactose and 7.6 g/l glucose using Gelidium amansii. The fermentation was performed with Pichia stipitis KCTC 7228 or Saccharomyces cerevisiae KCCM 1129. When wild P. stipitis and S. cerevisiae were used, the ethanol productions of 11.2 g/l and 6.9 g/l were produced, respectively. The ethanol productions of 16.6 g/l and 14.6 g/l were produced using P. stipitis and S. cerevisiae acclimated to high concentration of galactose, respectively. The yields of ethanol fermentation increased to 0.5 and 0.44 from 0.34 and 0.21 using acclimated P. stipitis and S. cerevisiae, respectively. Therefore, acclimation of yeasts to a specific sugar such as galactose reduced the glucose-induced repression on the transport of galactose.

• KSBB Journal
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• 제7권4호
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• pp.265-270
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• 1992

자연계에 널리 존재하는 저렴한 기질들은 대부분 여러 종류의 탄소원들을 함유한다. 이러한 혼합기질을 이용하는 효율적인 발효공정을 개발하기 위해서는 이들 기질들이 서로 어떻게 이용되는가를 알아야 하며, 사용되는 미생물의 생육과 생성물 생산을 잘 표현할 수 있는 동력학적 모델이 필요하다. P. stipitis에 의해 혼합기질에서 에탄오릉ㄹ 생산할 때 glucose는 xylose와 cellobiose 이용에 대해 ca-tabilite repression을 일으켰으며, 초기 glucose농도가 높을수록 xylose이용에서 균체의 생육속도는 감소하였으며 xylose이용시간도 길어졌다. 또한 glucose/xylose발효시 xylose이용에서 감소된 생육속도는 glucose가 xylose이용에 permenant repression을 야기시킨다는 것을 알 수 있었다. Cyclic AMP가 중개하는 catabolite repression mechanism에 기초하여 혼합기질에서 생육하는 P. stipitis의 생육모델을 발전시켰다 이 보텔식들을 이용하여 컴퓨터 simulation한 결과는 혼합기질로부터 P. stipitis에 의한 생육 및 에탄올 생성 실험결과와 비교적 잘 일치하였다.

• KSBB Journal
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• 제25권6호
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• pp.533-538
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• 2010

We investigated the effect of inhibitory compounds derived lignocellulosic hydrolysates on cell growth, sugar consumption and ethanol productivity, and also we intended to identify the potential for ethanol production based on lignocellulosic hydrolysates. Cell growth and ethanol production in the presence of acetate were initiated after 12 hr. Furans showed a longer lag time and phenolics showed a significant effect on strain and ethanol production in comparison to other model compounds. In the case of lignocellulosic hydrolysates, the acetate strongly affected cell growth and ethanol production.

• Biotechnology and Bioprocess Engineering:BBE
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• 제5권1호
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• pp.27-31
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• 2000

Characteristics of ethanol production by a xylose-fermenting yeast, Pichia stipitis Y-7124, were studied. The sugar consumption rate and specific growth rate were higher in the glucose-containing medium than in the xylose-containing medium. Specific activities of xylose reductase and xylitol dehydrogenase were higher in the medium with xylose than glucose, suggesting their induction by xylose. Maximum specific growth rate and ethanol yield were achieved at 30 g xylose/L concentration without formation of by-products such as xylitol and acetic acid whereas a maximum ethanol concentration was obtained at 130 g/L xylose. Adding a respiratory inhibitor, rotenone, increased a maximum ethanol concentration by $10\%$ compared with the control experiment. In order to evaluate the pattern of ethanol inhibition on specific growth rate, a kinetic model based on Luong's equations was applied. The relationship between ethanol concentration and specific growth rate was hyperbolic for glucose and parabolic for xylose. A maximum ethanol concentration at which cells did not grow was 33.6 g/L for glucose and 44.7 g/L for xylose.

• Journal of Microbiology and Biotechnology
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• 제20권5호
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• pp.946-949
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• 2010

The effects of two different sugars (glucose and xylose) on the expression levels and patterns of the xylose reductase (xyl1), xylitol dehydrogenase (xyl2), and xylulokinase (xyl3) genes were analyzed using Pichia stipitis. A significant increase in mRNA levels of xyl1 was observed after 6 h growth in culture conditions using xylose as a sole carbon source, but expressions of the three genes were not influenced by normal culture media with glucose. In addition, expressions of xyl2 and xyl3 were not observed during the entire culture period during which xylose was added. It also was found that the expression level of xyl1 increased as a function of the xylose concentration (40, 60, and 80 g/l) used in this study, indicating that xyl1 expression sensitively responded to xylose in the culture media. Although the induced level of xyl2 increased slightly after 48 h in the xylose-supplemented culture conditions, the expression of xyl2 was not observed in the xylitol-supplemented culture conditions. Finally, considering the expression of each gene in response to glucose or xylose, the absolute expression levels of the three genes indicate that xyl1 is induced primarily by exposure to xylose.

• KSBB Journal
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• 제15권2호
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• pp.113-119
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• 2000

본 연구에서는 높은 수율로 xylitol을 생산하기 위하여 P. stipitis CBS 5776으로부터 xylitol dehydrogenase (XDH)의 활성이 결여된 변이균주의 개발과 xylitol 발효 특성에 관한 실험을 수행하였다. EMS를 처리하여 XDH defective 변이균주인 PXM-4를 최종적으로 선별하였고, 변이균주 PXM-4의 XDH 활성을 측정하여 XDH 활성이 완전히 제거된 변이균주임을 확인하였다. 변이균주 PXM-4의 xylitol 발효에서 가장 적합한 cosubstrate로서 galactose를 선정하였다. Galactose와 xylose의 혼합당 배지에서 xylitol 생산이 오히려 낮아졌고, 20 g/L 이상에서는 xylitol 생산이 호히려 낮아졌고, 20 g/L의 xylose를 이용한 xylitol 발효에서 가장 적합한 galactose의 농도는 20 g/L 이었으며, 생산된 xylitol의 농도는 14.4 g/L 이었고, 수율은 97% 이었다. 또한 잔존하는 xylose를 완전히 xylitol로 전환시키기 위하여 xylitol 농도가 증가되지 않는 시기에 glalactose를 첨가함으로써 최종 xylotil 농도를 25 g/L 까지 향상시켰다. 옥수수 속의 산 가수분해 용액을 이용한 xylitol 발효에서 배지 내 존재하는 xylose는 모두 xylitol로 전환됨으로 확인하였다. 이와 같은 결과에 따라 XDH defective 변이균주를 개발함으로써 높은 수율의 xylitol 생산이 가능함을 확인하였다.

• 생명과학회지
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• 제27권12호
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• pp.1403-1409
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• 2017

본 연구에서는 lignocellulosic biomass (xylose)의 부가가치를 높이고 효율적인 활용을 위해 xylitol dehydrogenase를 Saccharomyces cerevisiae 숙주세포에서 분비 생산하고자 하였다. 먼저 S. cerevisiae와 Pichia stipitis유래 XYL2 유전자(S.XYL2 and P.XYL2 gene)의 발현 시스템을 구축하기 위하여 GAL10 promoter와 ADH1 promoter 하류에 각각 mating factor ${\alpha}$ ($MF{\alpha}$) signal sequence와 XYL2유전자를 가진 $pGMF{\alpha}-S.XYL2$, $pGMF{\alpha}-P.XYL2$, $pAMF{\alpha}-S.XYL2$와 $pAMF{\alpha}-P.XYL2$ plasmid를 구축하였다. 각각의 plasmid는 S. cerevisiae $SEY2102{\Delta}trp1$ 균주에 형질전환되었고, 생산된 xylitol dehydrogenase의 활성을 조사해 본 결과, GAL10 promoter가 ADH1 promoter보다 XYL2유전자의 발현에 더욱 적합함을 확인 할 수 있었다. 또한 P. stipitis 유래의 xylitol dehydrogenase 효소 활성이 S. cerevisiae 유래의 효소 활성보다 2배 이상 더 높았으며, 활성의 증가를 위해 두 유전자 모두 cofactor로 $NAD^+$에 의존한다는 것을 확인하였다. 재조합 유전자가 가지는 분비서열에 의해 $SEY2102{\Delta}trp1/pGMF{\alpha}-P.XYL2$ 균주에서 xylitol dehydrogenase의 약 77%는 periplasmic space로 분비 발현되었음을 알 수 있었다. 또한 재조합 xylitol dehydrogenase의 효율적인 생산을 위해 탄소원의 영향을 조사해본 결과, glucose 단독보다 glucose와 xylose를 혼합 배양한 경우에서 효소활성이 최대 41% 정도 증가되었음을 확인 할 수 있었다. 본 연구에서 최적화한 발현 시스템 및 배양 조건은 xylose 뿐만 아니라 다양한 biomass를 이용한 유용물질 생산을 위한 관련 단백질의 발현 분비시스템 구축 및 대량생산에도 응용될 수 있을 것이라 생각된다.

• 한국환경과학회지
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• 제21권1호
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• pp.97-103
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• 2012

Suspended wood waste was being inflow into the dam and the problem of waste disposal has been occurred. In this study, ethanol production using woody floater wastes was performed to estimate value in use for raw material of renewable energy. To achieve the goal, experiments of acid hydrolysis and ethanol fermentation using dam woody floater as raw materials for bioethanol was carried out. In the results of field survey in the chungju dam, kind of woody floater was mainly Japanese larch (Larix leptolepis) and hybrid poplar (Populus tomentiglandulosa). The results of sugar extraction showed that sugar content was higher in Larix leptolepis than Populus tomentiglandulosa. Extracted sugar from wood waste was effective consumed by yeast(P. Stipitis and S cerevisiae). In the experiment consumption of sugar including glucose, galactose and xylose, the consumption rate of S. cerevisiae is faster than that of P. stipitis. and efficiency for ethanol production is higer in S. cerevisiae than P. stipitis. Also it can be confirmed that resource as ethanol production using wood waste was available.

• KSBB Journal
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• 제25권4호
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• pp.401-407
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• 2010

We established a strategy for bioethanol production using the hydrolysate of rape stem, in which the inhibitor cocktail was added intentionally. The final goal of this study was to circumvent the detoxification process when the hydrolysate of lignocelluloisic biomass contained the toxic substances in high concentration. When six yeast strains were examined, Sacchromyces cerevisiae ATCC 96581 and Pichia stipitis CBS 7126 were relatively resistant to inhibitor cocktail. Then, using strains 96581 and 7126, we designed a process strategy for bioethanol production, assuming that the concentration of toxic substance in the hydrolysate of rape stem was remarkably high. When strains 96581 and 7126 were inoculated simultaneously, it was observed that strain 7126 produced bioethanol as well as strain 96581, although the concentration of inhibitor cocktail was 18.2% (v/v). Finally, throughout this co-cultivation of strains 96581 and 7126, bioethanol was produced about 6.0 (g/L), and bioethanol yield reached at 0.4 (g-bioethanol/g-reducing sugar) (78.4% of theoretical value).