A novel method for promoting antioxidant exopolysaccharidess production of Bacillus licheniformis

A novel method was described for improving the production of antioxidant extracellular polysaccharides from Bacillus licheniformis. Firstly, the tolerances of the strains to the organic solvents were investigated. Wild type strain of B. licheniformis OSTK95 and mutant strain UD061 can grow in a liquid medium in the presence of organic solvents with the log P value equal to or higher than 3.5 and 3.1, respectively. Secondly, the effects of different concentrations of n-hexane and xylene treatment on the extracellular polysaccharides excretion of both strains were studied. The maximum yield of the extracellular polysaccharides of B. licheniformis OSTK95 was 68.59 mg L−1 after treated by 10% n-hexane or 1% xylene for 3 h, while the maximum yield of the extracellular polysaccharides of strain UD061 was 185.01 mg L−1 after treated by 12.5% n-hexane or 5% xylene for 3 h. Finally, the continuous passage experiment showed that the strains have high genetic stability.