Background: Physical parameters like pH and temperature play a major role in the design
of an industrial enzymatic process. Enzyme stability and activity are greatly influenced by these
parameters; hence optimization and control of these parameters becomes a key point in determining
the economic feasibility of the process.
Objective: This study was taken up with the objective to optimize physical parameters for maximum
stability and activity of xylose reductase from D. nepalensis NCYC 3413 through separate
and simultaneous optimization studies and comparison thereof.
Methods: Effects of pH and temperature on the activity and stability of xylose reductase from Debaryomyces
nepalensis NCYC 3413 were investigated by enzyme assays and independent variables
were optimised using surface response methodology. Enzyme activity and stability were optimised
separately and concurrently to decipher the appropriate conditions.
Results: Optimized conditions of pH and temperature for xylose reductase activity were determined
to be 7.1 and 27 °C respectively, with predicted responses of specific activity (72.3 U/mg)
and half-life time (566 min). The experimental values (specific activity 50.2 U/mg, half-life time
818 min) were on par with predicted values indicating the significance of the model.
Conclusion: Simultaneous optimization of xylose reductase activity and stability using statistical
methods is effective as compared to optimisation of the parameters separately.