Optimization and characterization of an extracellular proteases from Aspergillus flavus "MTCC 277".

Abstract

The present study was undertaken to describe the optimization and characterization of proteases produced by, Aspergillus flavus MTCC 277. This strain exhibited the highest protease production after 4 days of incubation when grown on casein-containing basal salt medium. The optimum temperature of proteases was recorded at 35°C whereas optimum pH was 5 and 9. During the studies on the activity of enzyme with metal ions at 50 and 100 mM, Zn2+, Co2+and Fe2+ enhanced the enzyme activity and the rest ions showed inhibitory effect. Amongst twelve solvents, when used at the rate of 50 mM, formic acid showed maximum inhibition (0.00 U/ml) followed by formaldehyde (1.45 U/ml) and acetic acid (4.40 U/ml). Where as when the concentration was increased to 100 mM of all solvents, it greatly decreased the activity. A total of eight inhibitors were studied and reported that EDTA highly inhibited (4.15 U/ml) followed by urea (8.25 U/ml) and H2O2 (15.60 U/ml) at 50 mM concentration. When the concentration was increased to 100 mM all the inhibitors greatly repressed the activity. Zymographical analysis of this enzyme indicated that there are two alleles/loci responsible for proteases production and their relative mobility was P15.8 and P214.4.   Key words: Inhibitors, optimization, proteases, zymography.