Abstract:The fermentation broth of Xanthomonas campestris pv.campestris containing xanthan gum has a yellow color in the presence of xanthomonadin.This significantly affects the properties，yield，and extraction process of xanthan gum.Previous research obtained a naturally mutated strain of X.campestris，in which the synthesis of xanthomonadin was suppressed.Genome sequencing indicated that a mutation in the xanK gene altered the corresponding encoded aspartic acid to glycine.To investigate the effect of this mutation on the synthesis of xanthomonadin，wild-type xanK was introduced to the mutant strain for complementary expression.This resulted in the restoration of the synthesis of xanthomonadin，indicating that this mutation was responsible for the impaired xanthomonadin synthesis.Furthermore，it was found that the xanthan gum produced by the mutant strain exhibited higher viscosity and pyruvate content，but lower molecular weight and acetyl content compared with that produced by the wild-type strain.These results suggest xanthomonadin may have complex interactions in xanthan gum synthesis.