Sunday, May 3, 2009
2-10
Biological production of ethanol, xylitol, and arabitol by novel naturally occuring yeast
Azra Vajzovic, Renata Bura, and Sharon Doty. College of Forest Resources, University of Washington, Bloedel Hall 344, Box 352100, Seattle, WA 98195-2100
Up to date, there is no reported microorganism that is capable of utilizing both, hexose and pentose sugars at the same time, without being genetically modified or co-cultured. A novel, genetically unmodified yeast was identified as being capable of rapid assimilation and catabolism of five and six carbon sugars (arabinose, xylose, galactose, glucose and mannose). This yeast (PTD3) was shown not to be subject to hexose-mediated repression during mixed sugars fermentation. PTD3 produced ethanol of 82% of theoretical during fermentation of glucose, mannose and galactose. It produced considerable amount of xylitol of 96.1% of theoretical when xylose was present in the fermentation media and very high concentration of arabitol during fermentation of arabionse. The high ethanol, xylitol and arabitol yields were obtained without media, aeration, temperature and pH optimization.
This novel yeast has also a high tolerance of inhibitors (furfurals, 5-HMF and acetic acid) during biological production of ethanol and xylitol. PTD3 can effectively ferment five and six carbon sugars present in hydrolysates from different cellulosic biomass (steam pretreated switchgrass, hybrid poplar, and sugar cane bagasse) to ethanol, xylitol and arabitol.