Escherichia coli BL21(DE3) with adaptive mutation of xylR gene

When bacterial cells utilize mixed sugars in growth media, multi-growth phases can be observed due to the preference of sugar uptake and consumption, which is called diauxic growth. The delayed growth is inefficient because it is time lag in aspects of microbial biotechnology. Although Escherichia coli has been isolated from mammalian anaerobic guts, the physiology and metabolism of the model microorganism have been studied extensively under aerobic conditions because of convenience and manageability in the experiments. Anaerobic sugar metabolic regulation is still unclear and rarely studied. Therefore, in this study, sugar preference and metabolism of E. coli were studied under anaerobic conditions such as guts, which is the original habitat. In anaerobic conditions, when D-glucose and D-xylose added in the culture media, E. coli BL21(DE3) consumes D-glucose first, and D-xylose consumes very slowly. Adapted evolution were performed to alleviate the delay in the consumption of D-xylose and to find out the reason for the delay, and adapted strains with increased xylose consumption rate were obtained.