S.Radha, R.Himakiran Babu, A. Sridevi, N. B. L. Prasad3 and G. Narasimha
The acid protease productivity was enhanced by altering the genetic nature of wild type fungal strain A. niger by conventional mutation methods. Two methods viz. chemical and physical methods were employed to develop mutant strains on casein – agar medium. About eleven chemical mutant fungal strains were obtained with ethyl methane sulfonate (EMS) of concentration of 6.00 mg with exposure time of one hour. Similarly, nine physical mutant strains were developed by exposure of spore suspension of parent strain to UV irradiation for a period of 60.00 min. Formation of zone of casein clearance of 72 mm with UV mutant strain, UV4, 85mm with chemical mutant strains EMS4 and EMS6 and of 50 mm with parent strain were obtained. Total, twenty mutant strains were used for production of acid protease in submerged and solid state fermentation. Maximum acid protease activity (8.096U ml- 1) was noticed physical mutant strain UV9 in submerged fermentation whereas in solid state fermentation, peak acid protease activity was achieved with EMS11 (1094.5 ± 6.11 U g-1) followed by EMS4, EMS6 and UV4. But there no specific relation was drawn from caseinolysis and acid protease production. In solid state fermentation, 1.53 fold higher acid protease activity was achieved with chemical mutant EMS11 over wild type with the optimized media of parent strain. Similarly physical mutant UV9 also showed the enhanced protease activity by 2.01 fold than wild type under submerged fermentation.
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