Improvement of NADPH-Dependent Bioconversion by Transcriptome-Based Molecular Breeding†

Transcriptome data for a xylitol-producing recombinant Escherichia coli were obtained and used to tune up its productivity. Structural genes of NADPH-dependent d-xylose reductase and d-xylose permease were inserted into an Escherichia coli chromosome to construct a recombinant strain producing xylitol from d-xylose for use as a model system for NADPH-dependent bioconversion. Transcriptome analysis of xylitol-producing and nonproducing conditions for the recombinant revealed that xylitol production down-regulated 56 genes. These genes were then selected as candidate factors for suppression of the NADPH supply and were disrupted to validate their functions. Of the gene disruptants, that resulting from the deletion of yhbC showed the best bioconversion rate. Also, the deletion accelerated cell growth during log phase. The features of the mutant could be maintained in jar fermenter-scale production of xylitol. Thus, our novel molecular host strain breeding method using transcriptome analysis was fully effective and could be applied to improving various industrial strains.