Expression of AraE, an arabinose symporter, enhances xylose consumption in Bacillus subtilis and xylose-fermenting Saccharomyces cerevisiae

Xylose is one of abundant mono-sugars in cellulosic biomass. Therefore the ability to utilize xylose efficiently is a pre-requisite to develop robust microbial systems for biofuels and biochemicals production. In order to improve xylose-transporting ability, the araE gene coding for an arabinose:H⁺ symporter (AraE) was overexpressed in Bacillus subtilis 168 under the control of the xylA promoter and Saccharomyces cerevisiae DXSP under the GPD promoter. The resulting strain of B. subtilis JY123 utilized xylose as a sole carbon source efficiently, whereas B. subtilis JY121 control strain showed poor ability to use xylose. Especially B. subtilis JY123 showed 1.4-5.3 fold higher specific growth rates than B. subtilis JY121 control strain when using a mixture of glucose and xylose. Also S. cerevisiae DXSP/pGPD-AraE exhibited 22% higher xylose consumption rate and 2.1 times higher maximum xylitol productivity than S. cerevisiae control strain in a medium with a sole carbon source of xylose. These results indicated that AraE protein might be a potent xylose transporter and conferred higher xylose consuming ability to both B. subtilis and S. cerevisiae.