highly significantp < 0.001
The regression model for exo-PG production was highly significant (p < 0.001) with a satisfactory value of determination coefficient (R 2 = 0.9763), indicating that 97.63% of the variability in the response could be explained by the following second order polynomial equation: Y= 228.87 + 6.29 A + 6.10 B + 5.38 C – 7.98 D + 17.46 A 2 - 17.46 B 2 - 2.06 C 2 11.80 D 2 + 0.52 AB - 0.31 AC - 0.31 BC - 0.31 AD - 0.31 BD - 0.52 CD Where Y was the enzyme production (U/gds), A was the incubation period (days), B was the initial medium pH, C was the MHC (%) and D was the temperature (°C).