Inefficient transport of xylose into Saccharomyces cerevisiae is a major hurdle for production of xylitol, a natural sweetener with five carbons. To facilitate the xylose transport and hence increase xylose conversion to xylitol, the araE gene encodin...
Inefficient transport of xylose into Saccharomyces cerevisiae is a major hurdle for production of xylitol, a natural sweetener with five carbons. To facilitate the xylose transport and hence increase xylose conversion to xylitol, the araE gene encoding an arabinose:H+ symporter (AraE) from Bacillus subtilis and the XYL1 gene from Scheffersomyces stipitis were expressed in Saccharomyces cerevisiae EBY.VW4000, a hxt null mutant. The resulting strain (EXHA) exhibited 4.2 and 5.5 fold increases in xylose consumption rate and xylitol productivity, respectively, relative to the control strain without AraE. Also, overexpression of AraE in wild type S. cerevisiae D452-2 having all hexose transporters and XYL1 considerably increased both xylose consumption and xylitol production. In a glucose-limited fed-batch fermentation with intermittent addition of xylose, the DXXA strain with multiple copies of araE and XYL1 produced 177.8 g/L xylitol with 2.47 g/L-h productivity, which were 2.3 times higher than those for the same fed-batch culture of the DX strain expressing XYL1 only. Conclusively, B. subtilis AraE might be a potent xylose transporter and conferred much higher xylose-consuming and xylitol-producing abilities to S. cerevisiae.