嘌呤核苷磷酸化酶的表达及其在啤酒中的应用

为了开发一种能水解核苷的嘌呤核苷磷酸化酶（Purine Nucleoside Phosphorylase，PNPase），将其添加到糖化醪液中，增加麦汁中的游离嘌呤碱基质量浓度，在后续发酵阶段游离嘌呤碱基被酵母利用，提高了嘌呤物质的利用率，最终啤酒中的嘌呤质量浓度减少。将PNPase的编码基因deoD导入表达载体pET-28a（+）中，采用化学转化法将载体转入到大肠杆菌BL21（DE3）进行诱导表达，研究重组PNPase的活性，并将其应用到糖化工艺中。获得的重组PNPase活性为184.46 U/mL，添加到糖化醪液中后，麦汁中游离嘌呤碱基质量浓度升高，酵母可吸收的游离嘌呤质量浓度增多，啤酒发酵液嘌呤质量浓度显著降低，为后续研究使啤酒嘌呤含量的降低奠定了一定的基础。
To develop a purine nucleoside phosphorylase which can hydrolysis nucleoside. Adding purine nucleoside phosphorylase to the mash liquid，it could increase the free purine content in wort，which were utilized by yeast during the fermentation stage. As result，the utilization of purine could improve，purine content decreased in beer. The gene deoD encoding PNPase was cloned into the expression vector pET-28a（+） and the expression vector was transformed into E.coli BL21（DE3） using chemical transformation. The activity of recombinant PNPase was analyzed and it was applied to the mashing process. The results showed that the enzyme activity of obtained recombinant PNPase was 184.46 U/mL. When it was added to the mash liquid，the free purine content in wort was increased. Thus，yeast could use more free purine，purine content decreased significantly in beer，laing the foundation for the further reduction of purine content in beer