• KSBB Journal
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• 제24권5호
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• pp.439-445
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• 2009

목질계 바이오매스 전처리시 발생하는 저해물질로써 퓨란류, 유기산류, 페놀류를 포함한 발효에 있어, S. cerevisiae K35와 P. stipitis KCCM 12009가 에탄올 생산에 미치는 영향을 중심으로 연구를 수행하였다. 본 연구에 사용된 두 균주 모두 24시간 내에 100 g/L의 glucose를 모두 소비하였으며, 40 g/L 이상의 에탄올을 생산하였다. 저해물질로 퓨란 (5-HMF, furfural)류가 1-2 g/L 존재시, S. cerevisiae K35는 furfural에 비해 5-HMF에 의한 저해영향을 높았으며, P. stipitis KCCM 12009는 그와 반대의 경향을 보였다. Acetate가 5 g/L 이상 존재하는 경우, S. cerevisiae K35와 P. stipitis KCCM 12009 두 균주 모두에 균체량 및 에탄올 생산에 대한 저해정도가 가장 높았다. 또한, 페놀류 (syringaldehyde, vanillic acid, syringic acid)가 각각 1-2 g/L 존재시, S. cerevisiae K35는 비교적 적은 세포성장 저해영향과 소량 증가하는 에탄올 생산량을 보인 반면, P. stipitis KCCM 12009는 전반적으로 S. cerevisiae K35의 세포성장과 에탄올 생산에 있어 유사한 경향을 보였으나, syringaldehyde와 vanillic acid가 2 g/L 존재시에는 24시간에 균생장이 급격히 감소함과 동시에 에탄올 생산량도 감소함을 보였고, 48시간 배양 후 저해물질의 영향에서 벗어나 정상적인 세포성장과 에탄올을 생산하는 경향을 보였다. S. cerevisiae K35와 P. stipitis KCCM 12009에 동일한 농도의 저해물질이 존재시 저해영향의 차이를 보이는 것은 균주 자체의 특성 차이로 인한 저해물질에 대한 민감도를 나타내는 것으로 보인다. 본 연구를 통해 두 균주를 이용한 바이오에탄올 생산시 발생되는 저해물질의 농도별 선택적 특이성을 확인할 수 있었으며, 이를 통해 목질계 바이오매스 전처리시 발생되는 저해물질의 적정농도를 확인할 수 있었다.

• Journal of Microbiology and Biotechnology
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• 제32권11호
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• pp.1485-1495
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• 2022

The development of a yeast strain capable of fermenting mixed sugars efficiently is crucial for producing biofuels and value-added materials from cellulosic biomass. Previously, a mutant Pichia stipitis YN14 strain capable of co-fermenting xylose and cellobiose was developed through evolutionary engineering of the wild-type P. stipitis CBS6054 strain, which was incapable of co-fermenting xylose and cellobiose. In this study, through genomic and transcriptomic analyses, we sought to investigate the reasons for the improved sugar metabolic performance of the mutant YN14 strain in comparison with the parental CBS6054 strain. Unfortunately, comparative whole-genome sequencing (WGS) showed no mutation in any of the genes involved in the cellobiose metabolism between the two strains. However, comparative RNA sequencing (RNA-seq) revealed that the YN14 strain had 101.2 times and 5.9 times higher expression levels of HXT2.3 and BGL2 genes involved in cellobiose metabolism, and 6.9 times and 75.9 times lower expression levels of COX17 and SOD2.2 genes involved in respiration, respectively, compared with the CBS6054 strain. This may explain how the YN14 strain enhanced cellobiose metabolic performance and shifted the direction of cellobiose metabolic flux from respiration to fermentation in the presence of cellobiose compared with the CBS6054 strain.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.188.2-188.2
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• 2011

The use of renewable energy sources is becoming increasingly necessary to minimize the problems derived from the global warming impacts caused by the utilization of fossil fuels as well as their limited supply and reservoir. Also, localized heavy rain has occurred in many areas. As a result, suspended wood waste is being inflow into the dam and the problem of waste disposal has occurred. It is a unique renewable and alternative source for the production of energy. The experiment using wood waste (dry weight 25.0g) was conducted for extraction sugars such as xylose, lactose and glucose. For the sugar extraction from wood waste, hydrolysis experiment using wood waste was conducted by two steps. First step was reacted with 72% sulfuric acid (24.0N and 37.5 ml) for 1hr at $30^{\circ}C$ and second step was reacted at $105^{\circ}C$ for one hour after adding 2.45times of hot water. Extracted sugar was used in the experiment of sugar consumption to estimate feasibility of ethanol production using yeast(P. Stipitis and S cerevisiae). As a result, sugar extracted from wood waste was effective consumed by yeast(P. Stipitis and S cerevisiae). The consumption rate by yeast was S. cerevisiae was faster than that of P. stipitis. It can be confirmed that resource as ethanol production using wood waste was available.

• 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.

• Journal of the Korean Wood Science and Technology
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• 제40권4호
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• pp.294-301
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• 2012

본 연구는 농업 부산물인 옥수숫대를 이용하여 옥살산 전처리와 효소가수분해를 통한 에탄올 발효 효율 향상조건을 탐색하였다. 옥살산 전처리 옥수숫대의 효소가수분해는 Accellerase 1000을 이용하였으며, $50^{\circ}C$ 온도조건과 pH 4.5에서 96시간 가수분해하여 가장 높은 단당류 수율인 $64.8g/{\ell}$의 단당류 수율을 나타냈다. 옥수숫대에서 생산된 단당류의 발효에는 Pichia stipitis CBS 6054를 공시균주로 사용하였고, 전처리 옥수숫대 및 효소 투입량이 각각 10~14%와 15 FPU 이었을 때 효율적인 에탄올 생산에 가장 적합한 것으로 판명되었다. 이러한 조건에서 24시간 발효 후에 약 88.2%의 에탄올 전환율에 해당되는 0.45의 에탄올 수율을 얻었다.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 춘계학술발표대회
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• pp.41-44
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• 2000

Fermentation characteristics of recombinant Saccharomyces cerevisiae containing the xylose reductase gene from Pichia stipitis were analyzed in an attempt to convert xylose to xylitol, a natural five-carbon sugar alcohol used as a sweetener. Xylitol was produced with a maximum yield of 0.95 (g xylitol/g xylose consumed) in the presence of glucose that is used as a cosubstrate for cofactor regeneration. However addition of glucose caused inhibition of xylose transport and accumulation of ethanol. Such problems were solved by adopting glucose-limlted fed-batch fermentation. This process done with S, cerevisiae EHl3.15:pY2XR at$30\;^{\circ}C$ resulted in 105.2g/L xylitol concentration with maximum productivity of 1.69 g $L^{-1}$ $hr^{-1}$.

• Journal of Microbiology and Biotechnology
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• 제13권5호
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• pp.725-730
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• 2003

Three recombinant Saccharomyces cerevisiae strains showing different levels of xylose reductase activity were constructed to investigate the effects of xylose reductase activity and glucose feed rate on xylitol production. Conversion of xylose to xylitol is catalyzed by xylose reductase of Pichia stipitis with cofactor NAD(P)H. A two-substrate fermentation strategy has been employed where glucose is used as an energy source for NADPH regeneration and xylose as substrate for xylitol production. All recombinant S. cerevisiae strains Yielded similar specific xylitol productivity, indicating that xylitol production in the recombinant S. cerevisiae was more profoundly affected by the glucose supply and concomitant It generation of cofactor than the xylose reductase activity itself. It was confirmed in a continuous culture that the elevation of the glucose feeding level in the xylose-conversion period enhanced the xylitol productivity in the recombinant S. cerevisiae.

• Biotechnology and Bioprocess Engineering:BBE
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• 제10권4호
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• pp.346-352
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• 2005

The chemical characteristics, enzymatic saccharification, and ethanol fermentation of autohydrolyzed lignocellulosic material that was exposed to steam explosion were investigated using bagasse as the sample. The effects of the steam explosion on the change in pH, organic acids production, degrees of polymerization and crystallinity of the cellulose component, and the amount of extractive components in the autohydrolyzated bagasse were examined. The steam explosion decreased the degree of polymerzation up to about 700 but increased the degree of crystallinity and the micelle width of the cellulose component in the bagasse. The steam explosion, at a pressure of 2.55 MPa for 3 mins, was the most effective for the delignification of bagasse. 40 g/L of glucose and 20 g/L of xylose were produced from 100 g/L of the autohydrolyzed bagasse by the enzymatic saccharification using mixed cellulases, acucelase and meicelase. The maximum ethanol concentration, 20 g/L, was obtained from the enzymatic hydrolyzate of 100 g/L of the autohydrolyzed bagasse by the ethanol fermentation using Pichia stipitis CBS 5773; the ethanol yield from sugars was 0.33 g/g sugars.

• KSBB Journal
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• 제28권5호
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• pp.315-318
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• 2013

Ethanol fermentations were performed using separate hydrolysis and fermentation (SHF) processes with monosaccharides from pretreated seaweed, Eucheuma spinosum as the biomass. The pretreatment was carried out with 11% (w/v) seaweed slurry and 150 mM $H_2SO_4$ at $121^{\circ}C$ for 40 min. Enzyme hydrolysis after $H_2SO_4$ pretreatment was performed with Celluclast 1.5 L at $45^{\circ}C$ for 24 h. Five % active charcoal were added to hydrolysate to removed 5-hydroxy methylfurfural. Ethanol fermentation with 11% (w/v) seaweed hydrolysate was performed for 72~96 h using Kluyvermyces marxianus, Pichia stipits, Saccharomyces cervisiae and Candida tropicalis. Ethanol concentration was reached to 18 g/L by K. marxianus, 16 g/L by P. stipitis, 15 g/L by S. cerevisiae and 10 g/L by C. tropicalis, respectively. The ethanol yield from total monosugar was obtained 0.50 and ethanol productivity was obtained 0.38 g/L/h by K. marxianus.