Constitutive production of extracellular glucose isomerase by an osmophillic Aspergillus sp. under submerged conditions.

Abstract

We report constitutive production of glucose isomerase (GI) under submerged growth of Aspergillus sp. in glucose phosphate broth (GPB). The fungus produced significant quantities of extracellular GI in GPB without supplementing the inducer (xylose). The maximum biomass (872mg) and highest level of GI (1126U) were obtained in 42h at 30°C and 120rpm. Equal level of biomass and enzyme were produced in GPB with glucose and xylose, but the amount of biomass and enzyme was drastically reduced when the fungus was grown on other carbon sources. Optimum biomass, enzyme units and enzyme activity were obtained with 40 and 1g/l of glucose, respectively. Growth of Aspergillus sp. and enzyme synthesis even at high glucose concentration (60g/l) indicated the osmophillic nature of the fungus. Increasing the glucose concentration above 1 and 40g/l did not support the growth and enzyme activity. Among various organic and inorganic nitrogen sources used, yeast extract, peptone and NH4SO4 gave the best biomass and enzyme yields. Addition of Mg(2+) and Mn(2+) in GPB significantly enhanced the enzyme production. Under optimized conditions in modified GPB, the yield of biomass and synthesis and activity of GI were significantly enhanced.