초록
<P>Production of ethanol and xylitol from lignocellulosic hydrolysates is an alternative to the traditional production of ethanol in utilizing biomass. However, the conversion efficiency of xylose to xylitol is restricted by glucose repression, causing a low xylitol titer. To this end, we cloned genes <I>CDT-1</I> (encoding a cellodextrin transporter) and <I>gh1-1</I> (encoding an intracellular β-glucosidase) from <I>Neurospora crassa</I> and <I>XYL1</I> (encoding a xylose reductase that converts xylose into xylitol) from <I>Scheffersomyces stipitis</I> into <I>Saccharomyces cerevisiae</I>, enabling simultaneous production of ethanol and xylitol from a mixture of cellobiose and xylose (main components of lignocellulosic hydrolysates). We further optimized the expression levels of <I>CDT-1</I> and <I>XYL1</I> by manipulating their promoters and copy-numbers, and constructed an engineered <I>S. cerevisiae</I> strain (carrying one copy of <I>PGK1p-CDT1</I> and two copies of <I>TDH3p-XYL1</I>), which showed an 85.7% increase in xylitol production from the mixture of cellobiose and xylose than that from the mixture of glucose and xylose. Thus, we achieved a balanced co-fermentation of cellobiose (0.165 g/L/h) and xylose (0.162 g/L/h) at similar rates to co-produce ethanol (0.36 g/g) and xylitol (1.00 g/g).</P>