Discovery and characterization of novel D-xylose-specific transporters from Neurospora crassa and Pichia stipitis

作者：Du Jing; Li Sijin; Zhao Huimin^*

来源：Molecular Biosystems, 2010, 6(11): 2150-2156.

DOI：10.1039/c0mb00007h

Saccharomyces cerevisiae is considered one of the most promising organisms for ethanol production from lignocellulosic feedstock. Unfortunately, pentose sugars, which comprise up to 30% of lignocellulose, cannot be utilized by wild type S. cerevisiae. Heterologous pathways were introduced into S. cerevisiae to enable utilization of D-xylose, the most abundant pentose sugar. However, the resulting recombinant S. cerevisiae strains exhibited a slow growth rate and poor sugar utilization efficiency when grown on D-xylose as the sole carbon source. D-xylose uptake is the first step of D-xylose utilization. D-xylose can only enter yeast cells through hexose transporters, which have two orders of magnitude lower affinity towards D-xylose compared to hexoses. It was also shown that inefficient pentose uptake is the limiting step in some D-xylose metabolizing yeast strains. Here we report the cloning and characterization of two novel D-xylose-specific transporters from Neurospora crassa and Pichia stipitis. These two transporters were identified from a total of 18 putative pentose transporters. They were functionally expressed and properly localized in S. cerevisiae as indicated by HPLC analysis and fluorescence confocal microscopy, respectively. Kinetic parameters of the D-xylose-specific transporters were determined using a (14)C-labeled sugar uptake assay. Use of pentose-specific transporters should improve D-xylose consumption and ethanol production in fast D-xylose assimilating strains, thereby lowering the cost of lignocellulosic ethanol production.

• 出版日期2010