Article

World Journal of Microbiology and Biotechnology

, Volume 13, Issue 3, pp 341-346

Fermentation of corn fibre sugars by an engineered xylose utilizing Saccharomyces yeast strain

  • M. MoniruzzamanAffiliated withDepartment of Chemical Engineering, Texas A&M University
  • , B.S. DienAffiliated withNational Center for Agricultural Utilization Research, USDA, Agricultural Research Service, Fermentation Biochemistry Research Unit
  • , C.D. SkoryAffiliated withNational Center for Agricultural Utilization Research, USDA, Agricultural Research Service, Fermentation Biochemistry Research Unit
  • , Z.D. ChenAffiliated withDepartment of Chemical Engineering, Michigan State University
  • , R.B. HespellAffiliated withNational Center for Agricultural Utilization Research, USDA, Agricultural Research Service, Fermentation Biochemistry Research Unit
  • , N.W.Y. HoAffiliated withLORRE, Purdue University
  • , B.E. DaleAffiliated withDepartment of Chemical Engineering, Michigan State University
  • , R.J. BothastAffiliated withLORRE, Purdue University

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Abstract

The ability of a recombinant Saccharomyces yeast strain to ferment the sugars glucose, xylose, arabinose and galactose which are the predominant monosaccharides found in corn fibre hydrolysates has been examined. Saccharomyces strain 1400 (pLNH32) was genetically engineered to ferment xylose by expressing genes encoding a xylose reductase, a xylitol dehydrogenase and a xylulose kinase. The recombinant efficiently fermented xylose alone or in the presence of glucose. Xylose-grown cultures had very little difference in xylitol accumulation, with only 4 to 5g/l accumulating, in aerobic, micro-aerated and anaerobic conditions. Highest production of ethanol with all sugars was achieved under anaerobic conditions. From a mixture of glucose (80g/l) and xylose (40g/l), this strain produced 52g/l ethanol, equivalent to 85% of theoretical yield, in less than 24h. Using a mixture of glucose (31g/l), xylose (15.2g/l), arabinose (10.5g/l) and galactose (2g/l), all of the sugars except arabinose were consumed in 24h with an accumulation of 22g ethanol/l, a 90% yield (excluding the arabinose in the calculation since it is not fermented). Approximately 98% theoretical yield, or 21g ethanol/l, was achieved using an enzymatic hydrolysate of ammonia fibre exploded corn fibre containing an estimated 47.0g mixed sugars/l. In all mixed sugar fermentations, less than 25% arabinose was consumed and converted into arabitol.

AFEX corn fibre ethanol Saccharomyces