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复合酶体系在烟草固相基质上的酶解特性及助剂增效作用

Enzymolysis characteristics of a complex enzyme system on solid phase tobacco matrix and synergistic effect of an additive

  • 摘要: 为探究复合生物酶在烟草固相基质上的酶解动力学特性,揭示天然烟草基质的屏障效应,以及外源性助剂对酶解效率与烟叶品质的增效机理,在自建的复合人工烟叶上,通过非线性回归拟合一级降解动力学和米氏动力学经验近似模型,获得复合酶体系降解淀粉、蛋白质和纤维素的动力学基准参数。在自然烟叶上进行平行实验,通过对比两组体系的动力学参数变化,解析天然基质的抑制模式。在此基础上,引入外源性助剂,通过动力学分析、化学成分主成分分析(PCA)及感官质量评价,系统考察复合酶+助剂协同策略的增效作用。最后回归到复合人工烟叶上,比较分析助剂对酶促动力学参数的调控机制。结果表明,在复合人工烟叶上,复合酶对3种底物的降解呈现出不同的动力学特征。与复合人工烟叶相比,在自然烟叶中,淀粉降解受可及性限制,蛋白质降解受双重抑制,蛋白质米氏常数(Km)增至1.549 7%,最大反应速率(Vmax)降至0.015 5%/h;纤维素降解受构象/位阻限制,其Km降至22.724 5%,Vmax降至0.196 3%/h。助剂的加入提升了自然烟叶中淀粉、蛋白质和纤维素的一级降解速率常数(k),提升幅度分别为199.6%、695.0%和86.0%,并有效改变了烟叶的感官品质。助剂通过改变蛋白质的VmaxKm、提升淀粉底物可及性并改变纤维素的表观参数这3种动力学调控模式,发挥增效作用。可见,天然烟草基质屏障对不同大分子呈现出可由动力学参数表征的差异化抑制模式。外源性助剂作为一个微环境调节器,能通过多种可能的调控途径克服上述障碍,实现烟草大分子有效降解与界面微环境的协同调控。

     

    Abstract: The aim of the study was to investigate the enzymolysis kinetics of a complex enzyme system on a tobacco solid phase matrix, to elucidate the mechanism of the barrier effect of natural tobacco matrix and the synergistic effect and mechanism of an exogenous additive on enzymolysis efficiency and tobacco leaf quality. Using self-constructed composite artificial tobacco leaves, kinetic benchmark parameters for the degradation of starch, protein, and cellulose by a composite enzyme system were obtained through nonlinear regression fitting of first-order degradation kinetics and Michaelis-Menten kinetics empirical approximation models. The inhibition patterns of the natural matrix were analyzed by comparing the kinetic parameters between the artificial tobacco leaves and natural tobacco leaves. On this basis, the synergistic effect of a complex enzyme and additive strategy was systematically investigated through kinetic analysis, principal component analysis (PCA) of main chemical compositions, and sensory quality evaluation. Finally, the regulatory mechanism of the additive on enzymatic kinetic parameters was compared and analyzed by using the composite artificial tobacco leaves. The results showed that the degradation of the three substrates by complex enzyme system in composite artificial tobacco leaves exhibited different kinetic characteristics. Compared to the composite artificial tobacco leaves, starch degradation in natural tobacco leaves was accessibility-limited and protein degradation suffered from dual-inhibition, with Michaelis-Menten constant (Km) increasing to 1.549 7% and maximum reaction rate (Vmax) decreasing to 0.015 5%/h. Cellulose degradation was conformation/steric hindrance-limited, with Km decreasing to 22.724 5% and Vmax decreasing to 0.196 3%/h. The additive increased the first-order degradation rate constants (k) of starch, protein, and cellulose in natural tobacco leaves by 199.6%, 695.0%, and 86.0% respectively and effectively improved the sensory quality of the treated tobacco leaves. The additive exerted its synergistic effect through three different kinetic regulation modes which were the change of Vmax and Km for protein, the enhancement of substrate accessibility for starch, and the change of apparent kinetic parameters for cellulose. The natural tobacco matrix barrier presents differential inhibition patterns that can be characterized by kinetic parameters for different macromolecules. The exogenous additive acting as a micro-environment regulator can overcome these barriers through multiple possible regulatory pathways, achieving synergistic regulation of effective macromolecule degradation and interfacial microenvironment in tobacco.

     

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