Tuesday, April 30, 2013
Exhibit Hall
A co-fermenting strain with a capacity for efficient conversion of glucose and xylose to ethanol is indispensable to the commercialization of lignocellulosic ethanol industry. Xylose fermentation remains challenging due to the production yield and the complexity of lignocellulosic biomass hydrolysate, thus, improving the genetic stability of the xylose fermentability and the inhibitor tolerance of the recombinant xylose-fermenting microorganism are essential in the design of an economical cellulosic ethanol production process. A genetically engineered yeast YY5A with enhanced capacity to convert xylose to ethanol was recently obtained. Genetic stability of the recombinant yeast was previously investigated and results indicated that xylose can be used as a selection pressure to maintain the cell in the recombinant state. By adaptation in defined xylose medium for more than 30 subcultures, it was found that the genetic stability of the engineered strain has much improved. Evaluation on the metabolic capability toward xylose has shown that xylose consumption of the strain was increased 5.5% after adaptation. Fermentation result on the performance of the adapted recombinant strain indicated that ethanol yield was increase of 9.5% to achieve 0.46 g/g from xylose fermentation, and the byproduct xylitol yield was greatly decrease of 23% compared to the non-adapted strain. Furthermore, this recombinant yeast has been applied on various lignocellulosic materials for evaluating the fermentability. Optimization of the scale-up production and inhibitory tolerance levels of the strain are needed to be investigated.