Abstract The molecular mechanisms underlying the influence of nitrogen sources on xanthan gum production remain poorly understood. This study compared the effects of two nitrogen sources (NH 4 Cl and glutamate) on xanthan gum production in Xanthomonas campestris . Additionally, the transcriptomic responses to different glutamate concentrations during fermentation were investigated. The findings revealed that glutamate, particularly at a lower concentration of 1 g/L, significantly enhanced xanthan gum yield and viscosity. Comparative transcriptomic analysis across different fermentation stages revealed that nitrogen limitation, observed on day 4 under 1 g/L glutamate and day 6 under 2 g/L glutamate, favored xanthan gum biosynthesis. Furthermore, low glutamate concentration improved xanthan gum production primarily by altering nitrogen assimilation and redirecting carbon metabolic fluxes through modulation in the expression of genes ( rpoN , rpfC , and rpfG ) associated within two-component regulatory system. These results may provide valuable guidance for xanthan gum production using genetically engineered bacteria.
Wang et al. (Fri,) studied this question.