• Title/Summary/Keyword: Pichia

Search Result 321, Processing Time 0.043 seconds

Effect of chloride ions on the catalytic properties of human pancreatic α-amylase isozyme produced in Pichia pastoris (Pichia pastoris에서 생산된 인체 췌장 α-아밀레이스 동질효소의 촉매활성에 대한 염소이온의 영향)

  • Kim, Min-Gyu;Kim, Young-Wan
    • Korean Journal of Food Science and Technology
    • /
    • v.48 no.4
    • /
    • pp.341-346
    • /
    • 2016

  • The AMY2B gene, encoding human pancreatic ${\alpha}$-amylase isozyme (HPA II), was expressed in Pichia pastoris, and the effects of chloride ions on HPA II activity toward starch substrates were investigated. As seen with chloride ion-dependent ${\alpha}$-amylases-including HPA I, the isozyme of HPA II-chloride ions increased enzyme activity and shifted the optimal pH to an alkaline pH. The activity enhancement by chloride was more significant at pH 8 than that at pH 6, suggesting that the protonation state of the general acid/base catalyst of HPA II was important for the hydrolysis of starches at an alkaline pH because of the increase in its $pK_a$ by chloride ions. The turnover values for cereal starches as the substrates markedly increased in the presence of chloride by up to 7.2-fold, whereas that for soluble starch increased by only 1.7-fold. Chloride inhibited substrate hydrolysis at high substrate concentrations, with $K_i$ values ranging from 6 to 15 mg/mL.

  • https://doi.org/10.9721/KJFST.2016.48.4.341 인용 PDF KSCI

Enhancement of Xylitol Yield by Xylitol Dehydrogenase Defective Mutant of Pichia stipitis (Pichia stipitis의 Xylitol Dehydrohenase Defective Mutant에 의한 Xylitol 수율 향사)

  • Kim, Min-Soo;Kim, Chul;Seo, Jin-Ho;Ryu, Yeon-Woo
    • KSBB Journal
    • /
    • v.15 no.2
    • /
    • pp.113-119
    • /
    • 2000

  • In order to produce xylitol with high yield, experiments were carried out to develope xylitol dehydrogenase (XDH) defective m mutant from Pichia stipitis and to investigate the xylit이 fermentation characteristics of mutant strain. After treatment of P s stipitis with EMS, mutant PXM-4 was selected based on the XDH activity and xylitol production capability. Among the tested c cosubstrates, galactose was selected as an adequate cosubstrate on xyl뻐I production of mutant PXM-4. With the increase of galactose concentration, xylitol production was decreased because the transport of xylose into cell was inhibited by g galactose. The optimal concentration of galactose for the production of xylitol using 20 g/L xylose was 20 g/L. Under this c condition, maximum concentration of xylitol and yield were 14.4 g/L and 97%, respectively. In order to prevent the inhibitory e effect of xylose transport by galactose, galactose was fed with low concentration and the concentration of xylitol produced w was increased up to 25 g/L. In the fermentation of corn cob hydrolyzate by mutant PXM-4, xylose was completely converted t to xylit이 with a 100% yield in 4 days culture.

  • PDF

Expression System for Optimal Production of Xylitol Dehydrogenase (XYL2) in Saccharomyces cerevisiae (출아효모에서 xylitol dehydrogenase (XYL2)의 최적 생산을 위한 발현 시스템 구축)

  • Jung, Hoe-Myung;Kim, Yeon-Hee
    • Journal of Life Science
    • /
    • v.27 no.12
    • /
    • pp.1403-1409
    • /
    • 2017

  • In this study, the xylitol dehydrogenase (XYL2) gene was expressed in Saccharomyces cerevisiae as a host cell for ease of use in the degradation of lignocellulosic biomass (xylose). To select suitable expression systems for the S.XYL2 gene from S. cerevisiae and the P.XYL2 gene from Pichia stipitis, $pGMF{\alpha}-S.XYL2$, $pGMF{\alpha}-P.XYL2$, $pAMF{\alpha}-S.XYL2$ and $pAMF{\alpha}-P.XYL2$ plasmids with the GAL10 promoter and ADH1 promoter, respectively, were constructed. The mating factor ${\alpha}$ ($MF{\alpha}$) signal sequence was also connected to each promoter to allow secretion. Each plasmid was transformed into S. cerevisiae $SEY2102{\Delta}trp1$ strain and the xylitol dehydrogenase activity was investigated. The GAL10 promoter proved more suitable than the ADH1 promoter for expression of the XYL2 gene, and the xylitol dehydrogenase activity from P. stipitis was twice that from S. cerevisiae. The xylitol dehydrogenase showed $NAD^+$-dependent activity and about 77% of the recombinant xylitol dehydrogenase was secreted into the periplasmic space of the $SEY2102{\Delta}trp1/pGMF{\alpha}-P.XYL2$ strain. The xylitol dehydrogenase activity was increased by up to 41% when a glucose/xylose mixture was supplied as a carbon source, rather than glucose alone. The expression system and culture conditions optimized in this study resulted in large amounts of xylitol dehydrogenase using S. cerevisiae as the host strain, indicating the potential of this expression system for use in bioethanol production and industrial applications.

  • https://doi.org/10.5352/JLS.2017.27.12.1403 인용 PDF KSCI