《厦门大学学报（自然科学版）》

为探讨糖化共发酵同步进行的过程中发酵产物对纤维素酶活力的影响,研究了乳酸对纤维素酶组分中β-葡萄糖苷酶(BG)活力的影响.结果显示:乳酸对BG活力有不同程度的抑制,该作用具有显著的浓度效应,其半抑制浓度IC50=0.19 mol/L; 乳酸对BG的抑制类型是可逆的竞争性抑制,抑制常数KI=0.149 mol/L.应用底物反应动力学方法研究酶抑制动力学,建立了抑制动力学模型,发现乳酸对BG的影响是缓慢可逆失活的过程,底物对其有明显的保护作用,测得其正向速率常数k+0为0.4 L/(mol·min),逆向速率常数k-0为0.056 min-1.该结果为纤维素糖化共发酵进程调控提供了理论依据.

The kinetics of inhibition of β-glucosidase purified from Hypocrea orientalis by lactic acid has been studied.The results show that the enzyme can be reversiblely inhibited by lactic acid with IC50 of 0.19 mol/L,while at low concentration the inhibition of the enzyme is a slow,competitive type reaction and the inhibition constant(KI)is 0.149 mol/L.The microscopic rate constants for the reactions of lactic acid with the enzyme have been determined and the values of forward(k+0)and reverse(k-0)inhibition constants are 0.4 L/(mol·min)and 0.056 min-1,respectively.The presence of the substrate has showed an obvious protective effect on the enzyme against the inhibition by lactic acid.Our study provides the theoretical support for lactic acid production industry by simultaneous saccharification-fermentation of cellulose.

引言
1 材料与方法
2 结果与分析
3 讨论

图1 BG催化底物pNPG水解的动力学常数测定<br/>Fig.1 Determination of catalytic kinetic constants of BG for hydrolysis of pNPG

图1 BG催化底物pNPG水解的动力学常数测定
Fig.1 Determination of catalytic kinetic constants of BG for hydrolysis of pNPG

图2 乳酸对BG活力的影响<br/>Fig.2 Effect of lactic acid on BG activity

图2 乳酸对BG活力的影响
Fig.2 Effect of lactic acid on BG activity

图3 乳酸对BG活力的可逆抑制<br/>Fig.3 Reversible inhibition of lactic acid on BG activity

图3 乳酸对BG活力的可逆抑制
Fig.3 Reversible inhibition of lactic acid on BG activity

图4 乳酸存在下BG催化pNPG水解的Lineweaver-Burk曲线<br/>Fig.4 Lineweaver-Burk plots for hydrolysis of pNPG by BG under different concentrations of lactic acid

图4 乳酸存在下BG催化pNPG水解的Lineweaver-Burk曲线
Fig.4 Lineweaver-Burk plots for hydrolysis of pNPG by BG under different concentrations of lactic acid

图5 在不同浓度乳酸溶液中BG水解 pNPG的进程<br/>Fig.5 Time course of pNPG hydrolysis by BG under different concentrations of lactic acid

图5 在不同浓度乳酸溶液中BG水解 pNPG的进程
Fig.5 Time course of pNPG hydrolysis by BG under different concentrations of lactic acid

图6 不同底物浓度下乳酸对BG的抑制动力学进程<br/>Fig.6 Inhibition time course of lactic acid on BG in different concentrations of substrate

图6 不同底物浓度下乳酸对BG的抑制动力学进程
Fig.6 Inhibition time course of lactic acid on BG in different concentrations of substrate

图7 乳酸对BG的微观速率常数测定<br/>Fig.7 Determination of microscopic rate constants of lactic acid on BG

图7 乳酸对BG的微观速率常数测定
Fig.7 Determination of microscopic rate constants of lactic acid on BG

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引言

1 材料与方法

2 结果与分析

3 讨论

学报简介

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引言

1 材料与方法

2 结果与分析

3 讨 论

学报简介

3 讨论