双向单因素与田口法优化屎肠球菌产谷氨酸脱羧酶培养基

Optimization of Fermentation Medium for Glutamate Decarboxylase Production by Enterococcus faecium by Bidirectional One-Factor-at-a-Time and Taguchi Methods

采用双向单因素试验法及田口法,对屎肠球菌产谷氨酸脱羧酶(glutamate decarboxylase,GAD)的培养基进行了优化。结果表明,在筛选的4种培养基中,蛋白胨-蔗糖-牛肉膏(peptone-sucrose-beef extract,PSB)培养基最利于屎肠球菌产GAD,但其配方中的CaCl_2、K_2HPO_4和柠檬酸铵对GAD合成不利,蛋白胨、蔗糖、乙酸钠和谷氨酸一钠(monosodium glutamate,MSG)对GAD合成影响极显著(P<0.01),而牛肉膏对GAD合成影响不显著(P>0.10)。Minitab软件预测培养基的最优用量组合为蛋白胨15 g/L、牛肉膏10 g/L、蔗糖12.5 g/L、乙酸钠6.0 g/L、MSG 10 g/L、吐温80 1.0 g/L,预测300 m L发酵醪产GAD总活力为(399.30±12.51)U。经验证,GAD总活力为(384.26±10.32)U,与预测值没有显著性差异(P>0.05)。改良的PSB培养基的组分较优化前的PSB培养基显著减少,并更有利于GAD的合成,总酶活提高了45.71%。

The fermentation medium for glutamate decarboxylase（GAD） production by Enterococcus faecium was optimized by bidirectional one-factor-at-a-time and Taguchi methods. The results indicated that the peptone-sucrosebeef extract（PSB） medium was found to be the most suitable for GAD production among four tested media. However, Ca Cl2, K2 HPO4 and ammonium citrate in the PSB medium were unfavourable for GAD production. Peptone, sucrose, sodium acetate and monosodium glutamate（MSG） had significant effects on GAD production（P〈0.01）, which was not significantly affected by beef extract（P〈0.10）. The optimal culture medium predicted by Minitab software consisted of 15 g/L peptone, 10 g/L beef extract, 12.5 g/L sucrose, 6.0 g/L sodium acetate, 10 g/L MSG, and 1.0 g/L Tween 80. The predicted total GAD activity obtained by using the optimized medium was（399.30 ± 12.51） U, which was not significantly different from the experimental value（（384.26 ± 10.32） U）. The constituents of the modified PSB medium were much fewer compared with the initial one. However, the modified PSB medium was more suitable for GAD production, in which the total GAD activity produced by E. faecium was improved by 45.71% as compared to the initial one.