Polysaccharide is produced by a single stage continuous culture of Xanthomonas bacteria, especially of the Xanthomonas campestris group, in a chemically defined culture medium having a growth limiting nutrilite which is a nitrogen source selected from glutamic acid, asparagine, a glutamate salt or an asparagine salt. During the continuous process the culture has a mean residence time in the culture vessel of 16 hr 2/3 or less, preferably between 9 and 16 hr 2/3. The use of glutamic acid, asparagine, glutamate salt or asparagine salt as the limiting nitrogen nutrilite increases the output of polysaccharide at mean residence times of 16 hr 2/3 and below, when compared with the outputs achieved using inorganic nitrogen sources at the same mean residence times.