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 Methodologica l (RSM) study was conducted by employing a five-level, five variable, centr al composite rotatable design (CCRD) in order to understand the esterificat ion behavior of PPL in the lauroyl lactic acid synthesis. Five important va riables were considered, namely, enzyme/substrate (E/S) ratio (0.09 - 1.14 Activity Units/mmole - AU/mmol), lactic acid concentration (5-25 mmol), inc ubation 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 th e 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 va lidation with experimental yields when experiments corresponding to selecte d points on the contour plots were carried out. (C) 2001 Elsevier Science I nc. All rights reserved.