两步酶法生产γ-氨基丁酸的研究

提出两步酶法(包括发芽和均相反应2个阶段)生产γ-氨基丁酸(GABA)的新方法。以大豆为原料,采用两步酶法生产GABA,讨论了Ca2+对大豆发芽和均相反应过程中蛋白酶和谷氨酸脱羧酶活力,以及谷氨酸游离和GABA生成的影响。实验结果表明,不同浓度的Ca2+对这两种酶分别表现出激活和抑制作用。在发芽过程中,蛋白酶和谷氨酸脱羧酶的活力,以及GABA和游离谷氨酸的含量随发芽时间呈先上升后下降的趋势。在浸泡液CaCl2浓度3.0mmol/L、发芽时间60h的条件下,发芽大豆中GABA和游离谷氨酸的含量分别为111.9mg/(100g干物大豆)、224.8mg/(100g干物大豆)。在均相反应过程中,GABA和游离谷氨酸的含量增加。在固体含量20g/100mL、反应时间2h的条件下,游离谷氨酸含量在料液CaCl2浓度为1.0mmol/L时达到最大值369.9mg/(100g干物大豆),GABA含量在CaCl2浓度为3.0mmol/L时达到最大值316.1mg/(100g干物大豆)。采用两步酶法可充分发挥大豆内源酶的活力,生产出游离谷氨酸和GABA含量都较高的食品材料。

Study on the Production of γ-Aminobutyric Acid by Two-step Enzymatic

A two-step enzymatic method including a germination step and a following homogeneous reaction step was proposed for producing of γ-aminobutyric acid(GABA).GABA was produced with the novel method using soybean as the test material.Effects of Ca2+ on proteinase activity,glutamate decarboxylase(GAD) activity,glutamic-acid liberation and GABA production during the germination and homogeneous reaction were investigated.The experimental results showed that Ca2+ might activate or inhibit the enzymes,depending on its concentration.In the germination,proteinase activity,GAD activity,GABA content and free glutamic-acid content had an increasing period and a decreasing period.Under the condition of a CaCl2 concentration of soaking solution at 3.0 mmol/L and a germination time at 60 h,GABA content was 111.9 mg/(100 g dry soybean),and free glutamic-acid content was 224.8 mg/(100 g dry soybean).In the homogeneous reaction,the GABA and free glutamic-acid levels were further increased.Under the condition of a solid loading of reaction liquid at 20 g/100 mL and a reaction time at 2 h,the free glutamic-acid content reached a maximum of 369.9 mg/(100 g dry soybean) when the CaCl2 concentration of reaction liquid was 1.0 mmol/L,and the GABA content reached a maximum of 316.1 mg/(100 g dry soybean) when the CaCl2 concentration of reaction liquid was 3.0 mmol/L.It was clear that the interior enzymes of soybean could be fully activated,and food ingredients rich in free glutamic-acid and GABA could be effectively produced by using the two-step enzymatic method.