Earticle

초록

영어

Lignocellulosic materials, on pretreatment and hydrolysis, release monomeric glucose and xylose as the main sugars. While glucose can be fermented to ethanol efficiently by the brewer’s yeast Saccharomyces cerevisiae, the major pentose sugar xylose remains unutilized. However, the high content of xylose in hydrolysate streams necessitates the simultaneous bioconversion of both glucose and xylose for cost-effective production of ethanol. In most natural xylose-assimilating yeasts and fungi, xylose is metabolized via two consecutive redox reactions catalyzed by the predominantly NADPH-dependent xylose reductase and the NAD+-dependent xylitol dehydrogenase, with xylitol as the pathway intermediate. Such yeasts and recombinant S. cerevisiae strains harboring these genes can ferment xylose to ethanol anaerobically, but also produce considerable amounts of xylitol as byproduct due to cofactor imbalance resulting from the different coenzyme specificities of the two enzymes. In contrast, bacteria convert xylose directly to xylulose using the enzyme xylose isomerase which requires divalent metal ions as cofactors. However, bacterial xylose isomerases (XylA) which have so far been used are mostly thermophilic in nature and inactive or misfolded when expressed in yeast. We have developed a recombinant xylose-utilizing S. cerevisiae strain by co-expressing the genes for xylose isomerase (xylA) from the anaerobic fungus Orpinomyces, the endogenous S. cerevisiae xylulokinase (XKS) and the SUT1 sugar transporter from Pichia stipitis. The recombinant strain, designated as INVSc1/pRS406XKS/ pILSUT1/pWOXYLA was further adapted for improved xylose utilization by serial transfer in aerobic cultures in xylose containing minimal medium. The xylose-adapted strain was designated as ADAP8 and used for fermentation. The results of the studies on the performance of the genetically modified yeast on fermentation of glucose/ xylose mixtures and of biomass-derived hydrolyzate will be presented. The present study is, by far, the first report for the successful fermentation of a lignocellulosic hydrolysate by a xylose isomeraseexpressing
recombinant S. cerevisiae strain.

저자

• V. S.Bisaria [ Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology, New Delhi, India ]
• A.Kondo [ 2Department of Chemical Science & Engineering, Kobe University, Kobe, Japan ]
• A.Madhavan [ Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology, New Delhi, India ]
• A.Srivastava [ Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology, New Delhi, India ]

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간행물

표지보기 관심저널 등록

• 간행물명

  한국생물공학회 학술대회

• 간기

  반년간

• 수록기간

  1985~2013

• 십진분류

  KDC 476 DDC 576