Expression of Purine Nucleoside Phosphorylase and Its Application in Beer

Abstract:

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.