固定化唾液链球菌的酶学性质研究

以海藻酸钙为载体包埋唾液链球菌嗜热亚种Y-2的菌体细胞,对固定化细胞催化合成γ-氨基丁酸进行了较详细的研究。研究结果表明:固定化细胞谷氨酸脱羧酶(Glutamate decarboxylase,GAD)反应的最适温度为40℃,同时具有良好的温度稳定性。固定化细胞酶活最适反应pH为3.8。细胞经固定化后pH稳定性明显增加,GAD酶活回收率普遍高于游离细胞。0.1%Triton X-100具有较强的酶活促进作用。固定化细胞的GAD在酶促反应中并不存在底物抑制现象。在上述最优条件下进行菌体生产力测试,固定化细胞转化L-谷氨酸单钠盐11 h后,转化液γ-氨基丁酸的浓度达到了2.79 g/L。

Study on Enzymatic Characters of Immobilized Streptococcus salivarius

In this study,the cells of Streptococcus salivarius subsp.thermophilus Y-2 were embedded in calcium alginate,and the immobilized cells were used to synthesize γ-aminobutyric acid.The results showed that the optimum temperature for the reaction of glutamate decarboxylase(GAD) in the immobilized cells was 40 ℃,and it had good temperature stability;the optimum pH-value for GAD reaction was 3.8.In comparison with the free cells,the immobilized cells revealed obviously better pH stability and higher GAD activity recovery.The solution of 0.1% Triton X-100 had strong promotive effect on the activity of GAD.The reaction of GAD in the immobilized cells did not exist the substrate inhibition phenomenon.Under the above optimum conditions,the bacterial productivity test showed that the γ-aminobutyric acid content in the transformation solution reached 2.97 g/L after transforming L-MSG by the immobilized cells for 11 hours.