ZIF-8@纤维素酶-细胞共固定化体系的构建及强化丁酸合成的应用

Construction of ZIF-8@Cellulase-Cell Co-Immobilization System and Its Application in Enhancement of Butyric Acid Synthesis

酶-细胞共固定化作为多酶固定化策略的拓展,因其能分层包埋固定化酶和细胞不同生物分子从而强化系统催化性能,成为现阶段酶工程研究的新热点。为了将这一新技术用来强化丁酸的合成,作者基于仿生矿化法构建沸石咪唑酯骨架(zinc zeolitic imidazolate framework-8,ZIF-8)分隔包覆纤维素酶和酪丁酸梭菌(Clostridium tyrobutyricum,Ct),制备ZIF-8@纤维素酶-Ct共固定化体系。通过SEM、FT-IR、XRD等技术表征以及进行酶解、发酵实验的分析验证,该体系具有更优的同步糖化发酵性能。结果表明:在最适条件(40℃、pH 4.5)下,底物玉米芯水解率达56.02%,葡萄糖转化率为85.61%;进一步置于不同的pH和氧气体积分数下,发现有ZIF-8@纤维素酶包覆的细胞具有更高、更稳定的比生长率和相对细胞活力以及较低的相对活性氧水平,丁酸在32 h内产量达到6.74 g/L,比未固定化细胞提高了12.52%。

As an extension of multi-enzyme immobilization strategy,enzyme-cell co-immobilization has become a new hot topic in enzyme engineering research because of its ability to enhance the catalytic performance of the system by hierarchically encapsulating different biomolecules of immobilized enzymes and cells.In order to use this new technology to enhance the synthesis of butyric acid,zinc zeolitic imidazolate framework-8@cellulase-Clostridium tyrobutyricum(ZIF-8@cellulase-Ct)co-immobilization system was prepared by constructing ZIF-8 separated with cellulase and Ct based on biomimetic mineralization method.The system was characterized by SEM,FT-IR and XRD techniques and analyzed by enzymatic and fermentation experiments,which showed that the system had better simultaneous saccharification and fermentation performance.56.02%of corn cobs were hydrolyzed within at 40℃and pH 4.5,and the glucose conversion rate was about 85.61%.Placed under different pH and oxygen concentrations,cells with ZIF-8@cellulase coating were found to have higher and more stable specific growth rate,cell viability and lower relative reactive oxygen levels,and the final concentration of ZIF-8-SSF butyric acid yield reached 6.74 g/L in 32 h,which was 12.52%higher than that of non-immobilized cells.