Sunday, May 3, 2009
2-65
Transcriptomic analysis of carbohydrate metabolism during ethanol fermentation by Pichia stipitis
Wen-Heng Chen, Ting-Hsiang Lin, Gia-Luen Guo, and Wen-Song Hwang. Cellulosic Ethanol Program, Institute of Nuclear Energy Research, No. 1000, Wenhua Road, Jiaan Village, Longtan, Taoyuan, 32546, Taiwan
Pichia stipitis can ferment both glucose and xylose into ethanol and this organism has shown great potential for the development of novel co-fermentation processes designed to obtain lignocellulosic ethanol production. This study investigated the large-scale gene expression profiles during ethanol fermentation using different carbohydrate substrates. This was carried out by hybridization of cDNAs made from messenger RNA extracted from yeast samples during the fermentation against a specific and specially designed “Pichia stipitis microarray”. Analysis of the results showed that various genes involved in oxidative phosphorylation, pyruvate metabolism and the pentose phosphate pathway together with a number of high specificity pentose transporters were up-regulated significantly during xylose fermentation. On the other hand, genes involved in nucleic acid, amino acid and hexose metabolism were greatly up-regulated during glucose fermentation. These results suggest that ethanol production is the dominant pathway when xylose is being metabolized, but that assimilation is important during glucose metabolism. Further analysis of the various different pathways involved in carbohydrate metabolism indicated that improvements in high-specificity pentose transporter activity and the regulation of the expression levels of genes involved in ethanol production and the synthesis of cell biomass are necessary to further enhance the co-fermentation efficiency of Pichia stipitis. To our knowledge, this is the first report to explore global gene expression profiles during ethanol fermentation by Pichia stipitis that has used a specific “Pichia stipitis microarray”.