Production and characteristics of the exocellular polysaccharide in mutant strains ofXanthomonas fuscans

Production of the exocellular polysaccharide of the phytopathogenic bacteriumXanthomonas fuscans was investigated with respect to its possible use in utilization of industrial wastes containing lactose. Six stablelac ⁺ mutants were obtained after the treatment withN-methyl-N′-nitroso-N′-nitroguanidine. The mutants were compared with the parent strain. Morphological and cultivation characteristics, as well as production of the exooellular polysaccharide were compared. The production was found to be maximal during the stationary phase of growth in strains cultivated under submerged conditions. Gas chromatography revealed that the polysaccharide of the parent strain is formed by α- and β-D-glucose and α- and β-d-mannose with a small amount ofd-ribose and 6-deoxy-l-mannose. Composition of the polysaccharides produced by the mutant strains (lac ⁺) does not qualitatively differ from that of the parent strain. However, they were found to contain a higher quantity ofd-mannose, which is favourable for their industrial utilization.