• Journal of Microbiology and Biotechnology
• /
• 제21권1호
• /
• pp.109-114
• /
• 2011

In this study, we investigated the feasibility of producing bioethanol from the hydrolysate of rape stem. Specifically, the most ideal yeast strain was screened, and the microaeration was performed by surface aeration on a liquid medium surface. Among the yeast strains examined, Pichia stipitis CBS 7126 displayed the best performance in bioethanol production during the surface-aerated fermentor culture. Pichia stipitis CBS 7126 produced maximally 9.56 g/l of bioethanol from the initial total reducing sugars (about 28 g/l). The bioethanol yield was 0.397 (by the DNS method). Furthermore, this controlled surface aeration method holds promise for use in the bioethanol production from the xylose-containing lignocellulosic hydrolysate of biomass.

• KSBB Journal
• /
• 제9권4호
• /
• pp.395-399
• /
• 1994

Pichia stiJitis CBS5776를 이용하여 6탄당과 5 탄당을 함유한 혼합당 배지에서의 에탄올 발효 특성 을 알아 보기 위한 실험을 수행하였다. 탄소원으로 사용된 당 중 에탄올 수율변에셔는 포도당, man­n nose, galactose, xylose 순으로 5탄당보다는 6탄당 이 우수한 기절로 판명되었다. 포도당의 에탄올 수 율이 O.376g ethanol/g glucose로 제 일 높았으며, 다음으로 mannose의 에탄올 수율은 O.326g etha­nnol/g mannose이였다. Spent sulfite liquor와 같은 조성을 가진 혼합당 함유 배지에서 6탄당인 mannose, 포도당이 먼저 이용된 후 galactose와 5탄당인 xylose가 이용됨을 알 수 있었다. Arabinose가 단일 탄소원으로 존재할 경우, 일부가 균체 성장에 이용되였으나 혼합당 배지 에셔는 전혀 이용되지 못하였다. 발효 결과 최대 에 탄올 농도는 $12.2g/\ell$ 이었고, 에탄올 생산 수율은 0.332g ethanol/g sugar이었다.

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

• Journal of Microbiology and Biotechnology
• /
• 제23권10호
• /
• pp.1434-1444
• /
• 2013

We established a two-step production process using immobilized S. cerevisiae and P. stipitis yeast to produce ethanol from seaweed (U. pertusa Kjellman) hydrolysate. The process was designed to completely consume both glucose and xylose. In particular, the yeasts were immobilized using DEAE-corncob and DEAE-cotton, respectively. The first step of the process included a continuous column reactor using immobilized S. cerevisiae, and the second step included a repeated-batch reactor using immobilized P. stipitis. It was verified that the glucose and xylose in 20 L of medium containing the U. pertusa Kjellman hydrolysate was converted completely to about 5.0 g/l ethanol through the two-step process, in which the overall ethanol yield from total reducing sugar was 0.37 and the volumetric ethanol productivity was 0.126 g/l/h. The volumetric ethanol productivity of the two-step process was about 2.7 times greater than that when P. stipitis was used alone for ethanol production from U. pertusa Kjellman hydrolysate. In addition, the overall ethanol yield from glucose and xylose was superior to that when P. stipitis was used alone for ethanol production. This two-step process will not only contribute to the development of an integrated process for ethanol production from glucose-and xylose-containing biomass hydrolysates, but could also be used as an alternative method for ethanol production.

• KSBB Journal
• /
• 제26권4호
• /
• pp.311-316
• /
• 2011

We investigated the optimal surface aeration rate during bioethanol production from the hydrolysate of seaweed Sargassum sagamianum using Pichia stipitis. It was observed that, when the working volume was 880 mL in 2.5-L lab-fermentor, the surface aeration rates of 30 to 100 mL/min were the optimal values for bioethanol production, in which this surface aeration rate corresponded to less than 0.05 (1/min) as the oxygen transfer rate coefficient ($k_La$). In addition, during repeated-batch operation was carried out, we examined whether those surface aeration rates were the optimal for bioethanol production. It was also observed that the surface aeration rates of 30 to 100 mL/min in the working volume of 880 mL were the optimal values in terms of the cumulative bioethanol producrion and bioethanol yield. On the basis of the oxygen transfer rate coefficient it is probable that those surface aeration rates will be applied to the large-scale bioethanol production from the hydrolysate of seaweed Sargassum sagamianum.

• 생명과학회지
• /
• 제22권4호
• /
• pp.508-515
• /
• 2012

Cotton을 효모 세포($Pichia$ $stipitis$)의 고정화 담체로 사용하기 위하여 2-(diethylamino)ethyl chloride hydrochloride (DEAE HCl)로 derivatization 시켰다. 0.5 M DEAE HCl로 처리하였을 때, 효모 세포가 완전히 흡착하였으며, 이것은 DEAE-cotton g 당 101.8 mg의 효모 세포가 흡착하는 것이고, DEAE-cellulose에 효모 세포가 흡착하는 양의 약 6배 이상인 것으로 확인되었다. DEAE-cotton을 이용하여 효모 세포를 고정화하고, 이것을 ethanol 생산에 이용하였을 경우, glucose와 xylose가 포함된 배지에서 단당류에 대한 ethanol 수율로 0.33 정도로 ethanol을 생산 할 수 있다는 것을 실험적으로 확인하였다. 이를 이용하여 lignocellulosic bomass의 가수분해물로부터 bioethanol 생산에 이용될 수 있을 것으로 기대되어진다. DEAE-cotton에서 얻어진 결과는 DEAE-cellulose에서 같은 실험을 실시하여 서로 비교 분석하였다.

• 한국균학회지
• /
• 제39권3호
• /
• pp.243-248
• /
• 2011

6탄당과 5탄당을 이용할 수 있는 효모 Picha stipitis를 이용하여 해조류인 구멍갈파래 가수분해 추출물의 단당류로부터 바이오 에탄올을 생산하는 반복 회분식 공정에 대하여 연구하였다. 이러한 공정이 180시간 까지 반복적으로 이루어질 수 있었으며, 약 30 g/L의 총환원당으로 부터 최고 평균 11.9 g/L의 바이오 에탄올이 생산됨을 확인하였다. 이 때 바이오 에탄올 수율은 0.40 (DNS 방법 기준)과 0.37 (TLC 방법 기준)이었으며, 이는 이론치의 78.4%와 72.5%에 해당하는 바이오 에탄올 수율에 해당한다. 이 결과를 다른 측면에서 분석하면, 본 연구 결과로 얻어진 반복 회분식공정에서 건조 구멍갈파래 1 kg에서 39.67 g의 바이오 에탄올을 생산 할 수 있다는 결론을 얻게 되었다. 본 연구를 통하여 구멍갈파래의 가수분해 추출물로부터 바이오 에탄올을 생산할 수 있다는 것을 실험적으로 증명하였고, 상업적인 대량생산이 가능한 공정기술로서 반복 회분식 방법이 적합하다는 것을 확인할 수 있었다.

• Journal of Microbiology and Biotechnology
• /
• 제28권3호
• /
• pp.401-408
• /
• 2018

The waste seaweed from Gwangalli beach, Busan, Korea was utilized as biomass for ethanol production. Sagassum fulvellum (brown seaweed, Mojaban in Korean name) comprised 72% of the biomass. The optimal hyper thermal acid hydrolysis conditions were obtained as 8% slurry contents, 138 mM sulfuric acid, and $160^{\circ}C$ of treatment temperature for 10 min with a low content of inhibitory compounds. To obtain more monosaccharides, enzymatic saccharification was carried out with Viscozyme L for 48 h. After pretreatment, 34 g/l of monosaccharides were obtained. Pichia stipitis and Pichia angophorae were selected as optimal co-fermentation yeasts to convert all of the monosaccharides in the hydrolysate to ethanol. Co-fermentation was carried out with various inoculum ratios of P. stipitis and P. angophorae. The maximum ethanol concentration of 16.0 g/l was produced using P. stipitis and P. angophorae in a 3:1 inoculum ratio, with an ethanol yield of 0.47 in 72 h. Ethanol fermentation using yeast co-culture may offer an efficient disposal method for waste seaweed while enhancing the utilization of monosaccharides and production of ethanol.

• Journal of Microbiology and Biotechnology
• /
• 제10권4호
• /
• pp.564-567
• /
• 2000

A recombinant Saccharomyces cerevisiae, transformed with the genes encoding xylose reductase (XYL1) and xylitol dehydrogenase (XYL2) orginated from Pichia stipitis CBS 5776, was developed to directly convert xylose to ethanol. A fed-batch fermentation with the recombinant yeast produced 8.7 g ethanol/l with a yield of 0.13 g ethanol/g xylose consumed.