关键词: 海洋微生物, 地衣芽孢杆菌, 细菌胞外多糖, 优化, 抗氧化性

Abstract: [Objective] The aim of the study was to optimize the medium producing extracellular polysaccharide fromBacillus licheniformis XJ-2 and to investigate antioxidant properties of extracellular Polysaccharide. [Method] Single factor experiment was employed to explore the effects of carbon source,nitrogen source,pH and fermentation time on production of extracellular polysaccharide.The antioxidant characteristic of this polysaccharide was also investigated by the classical methods of Fenton and NADH-PMS-NBT. [Results] The optimal medium was shown as followed:sucrose 8% (w/v),nitrate 2% (w/v),pH 7.5 and fermentation time 84 h.Under the conditions,the yield of extracellular polysaccharide was 17.752 mg/mL. In addition,the polysaccharide had strong ability to clear ·OH and O₂^-·.The IC₅₀ of extracellular polysaccharide toward ·OH and O₂^-· were 2.0 mg/mL and 0.06 mg/mL,respectively. [Conclusion] The optimized medium significantly improved the yield of extracellular polysaccharide of Bacillus licheniformis XJ-2.The extracellular polysaccharide exhibited high antioxidant activities in vitro.Our results could provide some important data for commercial polysaccharide production and potentialapplication in immunomodulatory research.

Key words: marine microorganisms, Bacillus licheniformis, extracellular polysaccharides, optimization, antioxidant