固定化唾液链球菌生产γ-氨基丁酸的研究

PRODUCTION OF γ-AMINOBUTYRIC ACID BY IMMOBILIZED Streptococcus salivarius subsp.thermophilus Y-2

以唾液链球菌嗜热亚种(Streptococcus salivariussubsp.thermophilusY-2)为供试菌株,考察了卡拉胶、明胶和海藻酸钙等材料将此菌株固定化的效果,并通过比较固定化细胞的谷氨酸脱羧酶(glutamatedecarboxylase,GAD)活性及γ-氨基丁酸的产量和载体机械强度,确定了海藻酸钙作为固定化细胞的适宜载体。优化后得到的最适固定化条件(W/V)为:海藻酸钠2%,CaCl214%,菌体25%,凝胶平均颗粒直径1.64 mm,在此条件下测得固定化细胞的GAD活性为游离细胞的1.2倍。细胞多批次应用稳定性试验证明:固定化细胞较游离细胞有着更稳定的GAD活性,反复使用60 h后,固定化细胞GAD活性仍能保持其初始活性的90%以上,γ-氨基丁酸的积累量达到7.97 g/L。

For producing y-aminobutyric acid, the immobilized Streptococcus salivarius subsp, thermophilus Y-2. was used, and embedded in calcium alginate, carrageenan and gelatin. By comparing the glutamate decarboxylase （GAD） enzyme activity, yields of γ-aminobutyric acid and mechanical strength of the embeding materials（carriers）, the calcium alginate was selected as a suitable carrier for immobilization. The research results showed that the optimal immobilization condition for γ- aminobutyric acid production was that sodium alginate concentration was 2%, calcium chloride concentration 14%, and microbial concentration 25 % （W/V）, immobilized gelatin granule diameter 1.64mm. Under the condition, the GAD enzyme produced by immobilized cells was 1.2 times higher and its stability also higher than that of free ceils obviously. In shaking flasks, the immobilized cells GAD enzyme activity was kept above 90% and GABA content was 7.97g/L for 60 hours＇ cycle production.