Response surface methodology for optimization of medium components for extracellular protease production by Enterococcus faecalis InaCC B745

Enterococcus faecalis InaCC B745 was isolated from dadih, a traditional fermented milk from Bukittinggi, West Sumatra. Previous study shows that the lactic acid bacteria was able to produce protease. In this study, protease production was optimized using response surface methodology (RSM) with central composite design (CCD). The total of four variables and five-level combinations namely: 0-4% (w/v) of skim milk, 0-2 % (w/v) of yeast extract, 0-2 % (w/v) of glucose, and 0-2 % (w/v) of CaCO₃. Statistical analysis showed that the production of protease by E. faecalis InaCC B745 is significantly influenced by skim milk, yeast extract, glucose, and CaCO₃, combination of skim milk and yeast extract. The final concentrations of the optimized medium were 3% (w/v) skim milk, 1.5 % (w/v) yeast extract, 0.89 % (w/v) glucose, and 1.5 % (w/v) CaCO₃. Under these conditions, the model predicted of protease activity was 60.637 U/ml or around 57.3% increased.