Invertase Production by Irradiated Aspergillus niger OSH5 Using Agricultural Wastes as Carbon Source

Abstract

Aim: The objective of this study was to isolate microbial species having the ability for production of invertase enzyme and to study some optimal culture conditions for maximum invertase production by an isolate of Aspergillus niger OSH5 which showed the highest invertase activity among the screened isolates. The enhancement effect of gamma irradiation on invertase activity was also investigated. Place and Duration of Study: Plant Research Department, Nuclear Research Center, Atomic Energy Authority, Cairo, Egypt, between July, 2013 and January, 2014. Methodology: Seven microbial isolates were screened for invertase production. The most active isolate Aspergillus niger OSH5 was subjected to gamma irradiation mutagenesis to enhance invertase production. The optimal culture conditions including shaking speeds, temperature, incubation period, and pH were tested for maximum invertase production. Moreover, production of invertase using solid-state fermentation was also studied. Results: Among the seven isolates, A. niger OSH5 was found the most active on invertase production. The most effective carbon source in intracellular invertase production (14.8±1.27 u/ml) was sucrose at a concentration of 3% (w/v) using shaking speed of 150 rpm at 25ºC and pH 6.5 after incubation for 6 days. Among the screened agro-industrial wastes that were used as solid substrates for invertase production, wheat bran at a concentration of 14% (w/v) was the most conductive substrate for extracellular invertase production (15.9±2.44 u/g). Conclusion: The obtained results indicate the efficient use of low cost fermentation for invertase production by an A. niger isolate. Moreover, these findings indicate the efficient use of gamma irradiation as a tool for invertase production enhancement.