Abstract:In this study, α-L-rhamnosidase was purified from the product of solid-state fermentation of pomelo peel powder by Aspergillus niger and used to convert naringin to prunin. α-L-rhamnosidase was isolated and purified by precipitation using ammonium sulfate at concentrations ranging from 40% to 80%, hydrophobic interaction chromatography, affinity chromatography, and gel filtration chromatography. The enzyme was found to be a monomer with molecular weight of approximately 160 kDa and contained two polypeptides linked by a disulfide bond. The larger polypeptide had a molecular weight of 130 kDa. Naringin was hydrolyzed to prunin using this enzyme, and the optimal temperature and pH, Km, and Vmax were 50 ℃~60 ℃, 4.0~5.0, 0.24 μmol/mL, and 312.5 U/mL, respectively. The optimal hydrolysis time was 60~90 min and a conversion rate above 98% was achieved. The content of Prunin was accounted for more than 95% in the final product, while that of the byproduct naringenin was less than 5%. The approach of using α-L-rhamnosidase purified from Aspergillus niger solid-state fermentation products to prepare prunin shows advantages such as good thermostability, strong substrate affinity, high conversion rate, and fewer by-products, thus providing an important basis for the enzymatic production of prunin.
