Enhanced production and characterization of a novel β- D-glucose:oxygen-1-oxidoreductase by using <i>Aspergillus niger</i> UV-180-C mutant strain

Abstract

Along with other emerging health consequences, diabetes mellitus is one of the critical threats spreading all over the world with continuity. The investigation of glucose level in diabetic patients requires the key enzyme β-D-glucose:oxygen-1-oxidoreductase/glucose oxidase, where its optimized production by mutant derived strain could affect the economic burden and accuracy of the test. Wild type Aspergillus niger was subjected to ultraviolet radiation for enhanced production of glucose oxidase. It was found that UV-180-C is a potential mutant derived strain, screened by using 2-deoxy-Dglucose. Optimum production of glucose oxidase from A. niger UV-180-C was carried out by using CSL (2%), fermentation period (36 h), pH (5.5 and 4.5 for wild and mutant respectively), temperature (30°C), MgSO₄.7H₂O (0.0%), CaCO₃ (0.1%), KH₂PO₄ (0.8 and 1.0% for wild and mutant strains), Urea (0.3%). Crude enzyme was subjected to ammonium sulfate precipitation and resulted into 145.8 UmL^-1 activity. Glucose oxidase from mutant derived A. niger exhibited optimum pH at 6, temperature 20°C, K_m 10mM and V_max 142 UmL^-1. The pyridoxal phosphate caused significant inhibition to the enzyme which indicates the presence of lysyl residues near or at the active site of the enzyme from both wild and mutant derived strains.

Key words:Enhanced production, UV radiations, β-D-glucose:oxygen-1-oxidoreductase, A. niger