Comparison between Escherichia coli K-12 strains W3110 and MG1655 and wild-type E-coli B as platforms for xylitol production

Escherichia coli W3110 was previously engineered to produce xylitol from a mixture of glucose plus xylose by expressing xylose reductase (CbXR) and deleting xylulokinase (Delta xylB), combined with either plasmid-based expression of a xylose transporter (XylE or XylFGH) (Khankal et al., J Biotechnol, 2008) or replacing the native crp gene with a mutant (crp*) that alleviates glucose repression of xylose transport (Cirino et al., Biotechnol Bioeng 95:1167-1176, 2006). In this study, E. coli K-12 strains W3110 and MG1655 and wild-type E. coli B were compared as platforms for xylitol production from glucose-xylose mixtures using these same strategies. The engineered strains were compared in fed-batch fermentations and as non-growing resting cells. Expression of CRP* in the E. coli B strains tested was unable to enhance xylose uptake in the presence of glucose. Xylitol production was similar for the (crp*, Delta xylB)-derivatives of W3110 and MG1655 expressing CbXR (average specific productivities of 0.43 g xylitol g cdw(-1) h(-1) in fed-batch fermentation). In contrast, results varied substantially between different Delta xylB-derivative strains co-expressing either XylE or XylFGH. The differences in genetic background between these host strains can therefore profoundly influence metabolic engineering strategies.