PVA/CNTs/ZnO固定化L-AI和β-GAL双酶级联高效绿色制备D-塔格糖的应用研究

    Application of PVA/CNTs/ZnO carrier immobilized L-AI and β-GAL dual-enzyme cascade to the efficient green preparation of D-tagatose

    • 摘要: 为提高D-塔格糖的产量,首先从土壤样本中筛选并鉴定可高效产L-阿拉伯糖异构酶(L-arabinose isomerase,L-AI)的微生物菌株,随后通过araA基因克隆异源表达获得L-AI,并通过制备PVA/CNTs/ZnO固定化载体负载L-AI与β-半乳糖苷酶(β-Galactosidase,β-GAL)构建PVA/CNTs/ZnO@L-AI@β-GAL多酶反应体系,以提高D-塔格糖的合成效率。通过扫描电镜(SEM)、热重(TG)、红外光谱(FTIR)和X射线光电子能谱(XPS),分析PVA/CNTs/ZnO固定化载体性能,并探讨PVA/CNTs/ZnO@L-AI@β-GAL的温度和pH等酶学性质。从土壤中筛选获得一株高产D-塔格糖的菌株,经鉴定分析为Bacillus amyloliquefaciens,命名为LW 48,并在大肠杆菌中异源表达该菌株的araA基因得到L-AI。对PVA/CNTs/ZnO固定化载体的SEM、TG、FTIR和XPS表征分析表明PVA/CNTs/ZnO载体具有优良的稳定性。酶学性质分析表明,级联双酶L-AI和β-GAL的最佳温度和pH分别为65 ℃、pH 7.0,动力学参数vmax为0.187 g·L-1·s-1Km为6.02 g·L-1;游离双酶L-AI和β-GAL的vmax为0.230 g·L-1·s-1Km为22.95 g·L-1。此外,固定化级联双酶L-AI和β-GAL的最大转化率为42.9%,比游离双酶L-AI和β-GAL提高了约3倍。通过制备PVA/CNTs/ZnO载体提升了级联双酶L-AI和β-GAL生产D-塔格糖的水平,为D-塔格糖及稀有糖的工业化高效绿色生物制造提供一种新的途径。

       

      Abstract: To improve the yield of D-tagatose, in this study, from soil samples, the initial step was to screen and identify microorganisms capable of efficiently producing L-arabinose isomerase (L-AI). Subsequently, the gene of araA was cloned and heterologously expressed to obtain L-AI. To enhance the synthesis efficiency of D-tagatose, L-AI and β-galactosidase (β-GAL) were co-immobilized with the prepared PVA/CNTs/ZnO carrier to construct the multi-enzyme reaction system. In addition, PVA/CNTs/ZnO immobilization carrier was analyzed by scanning electron microscopy (SEM), thermogravimetric (TG), infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Furthermore, the temperature and pH of PVA/CNTs/ZnO@L-AI@β-GAL were investigated. In this study, the high-yielding D-tagatose strain named LW 48, which was identified as Bacillus amyloliquefaciens. The recombinant protein L-AI was obtained by cloning and expression. Dual-enzyme cascade of β-GAL and L-AI immobilized on the PVA/CNTs/ZnO carrier was expressed and analyzed by SEM, TG, FTIR and XPS characterization. The results showed that the PVA/CNTs/ZnO carrier had excellent stability. When lactose was used as substrate, the optimal temperature and pH of L-AI were 65 ℃ and pH 7.0, respectively. The kinetic parameters on the vmax of dual-enzymes cascade (β-GAL and L-AI) was 0.187 g·L-1·s-1, and the Km was 6.02 g·L-1. The kinetic parameters on the vmax of the free enzymes (β-GAL and L-AI) was 0.230 g·L-1·s-1 and the Km was 22.95 g·L-1. After 24 h of the reaction under the optimal conditions, the maximum conversion rate of the free enzymes was 13.2%, and the maximum conversion rate of dual-enzymes cascade was 42.9%. The conversion rate of the latter was significantly higher (about 3 times) than that of the former. In our research, with the preparation of PVA/CNTs/ZnO carrier, the biosynthesis level of dual-enzymes cascade of β-GAL and L-AI for green production of D-tagatose was effectively improved, providing a new approach for industrial of D-tagatose and rare sugars with the efficient green bio-manufacturing.

       

    /

    返回文章
    返回