Transcriptomic response of Xanthomonas campestris during xanthan gum production to glutamate concentration

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 (NH₄Cl 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.