초록
<P><B>Abstract</B>Background<P>The optimization of metabolic pathways is critical for efficient and economical production of biofuels and specialty chemicals. One such significant pathway is the cellobiose utilization pathway, identified as a promising route in biomass utilization. Here we describe the optimization of cellobiose consumption and ethanol productivity by simultaneously engineering both proteins of the pathway, the β-glucosidase (gh1-1) and the cellodextrin transporter (cdt-1), in an example of pathway engineering through directed evolution.</P>Results<P>The improved pathway was assessed based on the strain specific growth rate on cellobiose, with the final mutant exhibiting a 47% increase over the wild-type pathway. Metabolite analysis of the engineered pathway identified a 49% increase in cellobiose consumption (1.78 to 2.65 g cellobiose/(L · h)) and a 64% increase in ethanol productivity (0.611 to 1.00 g ethanol/(L · h)).</P>Conclusions<P>By simultaneously engineering multiple proteins in the pathway, cellobiose utilization in <I>S. cerevisiae</I> was improved. This optimization can be generally applied to other metabolic pathways, provided a selection/screening method is available for the desired phenotype. The improved <I>in vivo</I> cellobiose utilization demonstrated here could help to decrease the <I>in vitro</I> enzyme load in biomass pretreatment, ultimately contributing to a reduction in the high cost of biofuel production.</P></P>