STATISTICAL OPTIMIZATION OF HALOTOLERANT PROTEASE PRODUCTION FROM A NEW BACILLUS SUBTILIS STRAIN AJ ISOLATED FROM A SALT PAN

摘要

Halotolerant keratinolytic proteases producing bacterial isolates were screened from the saltpan in Tamilnadu, India. Among the 59 proteolytic bacterial isolates, Bacillus subtilis strain AJ showed maximum keratinolytic protease activity. The medium components (carbon source, nitrogen source and ions) and physical factors (pH and sodium chloride), which play an important role in the production of enzyme, were selected as the main factors in a two-level full factorial design, based on one variable ata time approach. The medium pH, sodium chloride, fructose, yeast extract and MnClj positively influenced on keratinase activity. Central Composite Design (CCD) and Response surface methodology (RSM) was employed for the optimization of different nutritional parameters (pH, fructose and yeast extract) influencing production of keratinolytic protease by newly isolated Bacillus subtilis strain AJ in submerged fermentation. The Model F-value for keratinolytic activity was 62.08 implied that the designed model was significant (p<0.05). The predicted maximum keratinolytic activity was 689.5 U/mL. To confirm the predicted result, the experiments performed using the optimized conditions produced 674.3 U/mL of enzyme. This experimental result (674.3 U/mL) was in good agreement with that of the predicted one (689.5 U/mL) validated the model. RSM-optimized medium increased twofold of keratinolytic activity than the unoptimized medium.