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| Optimization of recombinant Escherichia coli EGs2 fermentation condition affecting β-glucanase production and Studies on Enzyme Characteristics |
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Abstract Abstract: The fermentation conditions of mutant EGs2 (obtained from directed evolution for thermostable β-glucanase) for β-glucanase production were investigated with orthogonal experiment.Fermentation was conducted in 250 mL flask, each containing 30 mL of medium contained Whey 10 g•L-1,Yeast extract 5 g•L-1,NaCl 10 g•L-1,the temperature was 37 ℃.The optima culture conditions were as following: initial pH value 6.0, shaking speed 170 r•min-1,inoculation volume 1 %,inoculation time 12 h.β-glucanase production by mutant EGs2 was associated with cell growth and biomass,β-glucanase activity was increased significantly when cells entered growth phase.The bacterium began the stable phase after cultured for 14 h with the highest biomass 1.71 g•L -1 and β-glucanase activity 321.56 U•ml-1.When β-glucan was used as a substrate,the optimum temperature and pH were respectively 60 ℃ and 6.0.After 20 min incubation at 40 ℃,50 ℃,55 ℃,60 ℃,65 ℃,70 ℃, the residual activity remained at least 80%.After 48 h conservation at pH 5.0-9.0,the residual activity remained at least 90%.The enzyme was stable below 70 ℃ and at pH 5.0-9.0.
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Received: 25 December 2006
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