Adaptive laboratory evolution induced novel mutations in Zymomonas mobilis ATCC ZW658: a potential platform for co-utilization of glucose and xylose

A systematic adaptive laboratory evolution strategy was employed to develop a potential Zymomonas mobilis strain with the ability to co-utilize glucose and xylose. Z. mobilis ATCC ZW658, a recombinant xylose fermenting strain, was subjected to adaptive laboratory evolution over a period of 200 days under strict selection pressure of increasing concentration of xylose. The evolved strain exhibited 1.65 times increase in the overall specific xylose utilization rate when compared with the parent strain. Furthermore, the strain displayed significantly improved performance in terms of co-fermentation of xylose in the presence of glucose with specific glucose and xylose utilization rate of 1.24 g g(-1) h(-1) and 1.34 g g(-1) h(-1), respectively. Altered phenotypic response of the evolved strain, in terms of improved xylose utilization, co-utilization of mixed sugars, enhanced growth, ethanol production, and reduced xylitol production has been explained by novel mutations, identified using next-generation sequencing, in xylose assimilating, metabolizing, and crucial regulatory pathway genes and key enzyme activity assays.