Effect of pH and substrate concentration on the cellulase
activity
The interactive effect of pH and substrate concentration can be
investigated from the 2D contour plot (Fig. 8). The response point
tends to lie towards the higher substrate concentration indicating
that concentrations were set such that the selected pH and substrate
concentration were optimum or close to optimum for other
variables. The contours indicate that the cellulase activity increased
with varying pH and substrate concentration, holding the other
variables.Maximumcellulase activity was observed 9.48 U/ml from
superimposing contour plots response at pH 5.0 and substrate concentration
90 mg/ml. Cellulase activity decreased with increase in
pH and increasing substrate concentration has no significant effect
on cellulase activity. The non-significant value and zero interaction
coefficients between pH and substrate concentration from regres-
Fig. 8. Contour plot showing the interactive effect of substrate and pH on the cellulase
activity at 65 ◦C and enzyme concentration 550l/ml.
Fig. 9. Contour plot showing the interactive effect of substrate and enzyme concentration
on the cellulase activity at 65 ◦C and pH 7.5.
sion model also indicated that these variables do not interact with
each other (Eq. (4)).