Improving glucose and xylose assimilation in Azotobacter vinelandii by adaptive laboratory evolution

Azotobacter vinelandii is a microorganism with biotechnological potential because its ability to produce alginate and polyhydroxybutyrate. Large-scale biotechnological processes are oriented to sustainable production by using biomass hydrolysates that are mainly composed by glucose and xylose. In the present study, it was observed that A. vinelandii was unable to consume xylose as the sole carbon source and that glucose assimilation in the presence of xylose was negatively affected. Adaptive Laboratory Evolution (ALE) was used as a metabolic engineering tool in A. vinelandii, to improve both carbohydrate assimilation. As a result of ALE process, the CT387 strain was obtained. The evolved strain (CT387) grown in shaken flask cultivations with xylose (8 g L^-1) and glucose (2 g L^-1), showed an increase of its specific growth rate (µ), as well as of its glucose and xylose uptake rates of 2, 6.45 and 3.57-fold, respectively, as compared with the parental strain. At bioreactor level, the µ, the glucose consumption rate and the relative expression of gluP that codes for the glucose permease in the evolved strain were also higher than in the native strain (1.53, 1.29 and 18-fold, respectively). Therefore, in the present study, we demonstrated the potential of ALE as a metabolic engineering tool for improving glucose and xylose consumption in A. vinelandii.