A central composite rotatable design analysis of lipase catalyzed synthesis of lauroyl lactic acid at bench-scale level

Porcine Pancreas lipase (PPL) was employed for the reaction between lactic acid and lauric acid at bench-scale level. A Response Surface Methodological (RSM) study was conducted by employing a five-level, five variable, central composite rotatable design (CCRD) in order to understand the esterification behavior of PPL in the lauroyl lactic acid synthesis. Five important variables were considered, namely, enzyme/substrate (E/S) ratio (0.09 - 1.14 Activity Units/mmole - AU/mmol), lactic acid concentration (5-25 mmol), incubation period (6-51 h), buffer volume (0-0.2ml) and buffer pH Values (4.0-8.0). Highest ester yield of 6.8 mmol was predicted at the lowest EIS ratio of 0.09 AU/mmol. Lower E/S ratios gave higher yields and higher E/S ratios gave lesser yields. This behavior clearly explained the competitive nature of binding between lauric and lactic acids for the same binding site on the enzyme. Addition of buffer in terms of both volume and pH did not have a profound effect on increase in ester yield. Predicted yields showed good validation with experimental yields when experiments corresponding to selected points on the contour plots were carried out. (C) 2001 Elsevier Science Inc. All rights reserved.