A carotenoid-free mutant strain of Sphingomonas paucimobilis ATCC 31461 for the commercial production of gellan

Gellan, an exopolysaccharide produced by Sphingomonas paucimobilis ATCC 31461, is used in the food, pharmaceutical, and other industries. During the fermentative production of gellan, strain ATCC 31461 also accumulates large amounts of yellow carotenoid pigments, thereby increasing processing costs. A carotenoid-free mutant strain of ATCC 31461 was isolated by ethyl methanesulfonate mutagenesis combined with ultraviolet irradiation. A new gellan purification method which reduced the consumption of isopropanol was developed based on this mutant strain. The final gellan production of the mutant strain was 13% higher than that of the parent strain. The glycerate and acetate substituents of gellan produced by the mutant strain were 17% and 65% higher than those produced by gellan from ATCC 31461, respectively. Stability tests suggested that the broth produced by the mutant strain was more stable during storage at room temperature compared with that produced by the parent strain. The mutant strain seems to be an ideal strain for use in the commercial production of gellan.