Applications of surface plots and statistical designs to selected lipase catalysed esterification reactions

Abstract

The usefulness of several statistical designs in experimental optimisation including Box-Behnken, Central Composite Rotatable and Plackett–Burman designs in lipase catalysed esterification reactions is presented. Analyses of several response surface plots obtained by employing statistical designs in lipase catalysed esterification reactions have indicated that such plots could be grouped into four types to explain esterification behaviour in the presence of different kinds of substrates and reaction conditions. Similarly, a Plackett–Burman design helps in the selection of the most probable organic acid or alcohol in a mixture, for a facile esterification reaction. Predominant acid binding in preference to alcohol gives rise to dome-shaped response surface plots. Predominant alcohol binding in preference to acid give rise to inverted dome-shaped plots. The competitive and inhibitory nature of substrates are brought out clearly in response surface plots. Rate plots show linear relationships between time and substrate with smooth surfaces within the limits of the variables employed. There are other uneven plots, which reflect the effect of variables like buffer pH, buffer volume and temperature on the activity of lipase employed. The stability of lipases under drastic esterification conditions of temperature and solvents was also studied.