Optimization of fermentation conditions for extracellular polysaccharide production by Pseudomonas syringae Y11 and its antioxidant activity
In order to improve the yield of extracellular polysaccharide(EPS)by liquid fermentation of Pseudomonas fulva,using extracellular polysac-charide yield as an evaluation index,the EPS production conditions of the strain were optimized by single factor and response surface tests,and the antioxidant properties of the EPS were investigated.The results showed that the optimal conditions for the production of extracellular polysaccharides by P.fulva were maltose 44 g/L,soybean peptone 11 g/L,sodium dihydrogen phosphate 8 g/L,inoculum 4％,rotational speed 160 r/min,fermenta-tion temperature 28 ℃,time 72 h,and initial pH 7.0.The yield of EPS under the optimal conditions was 4.56 g/L,which was 3.7 times that of before optimization.The results of antioxidant activities showed that EPS had good scavenging activity on DPPH radicals,ABTS radicals,hydroxyl radicals,and superoxide anion radicals in a certain concentration range.When the mass concentration of EPS was 2.5 mg/ml,the scavenging ability of EPS on DPPH radicals,ABTS radicals,hydroxyl radicals,and superoxide anion radicals was(70.83±1.80)％,(45.00±1.73)％,(65.83±1.80)％,and(44.6± 2.11)％,respectively,which indicated that the EPS produced by the liquid fermentation of P.fulva had certain antioxidant activity.
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