Kinetic study on esterification of palmitic acid catalyzed by glycine-based crosslinked protein coated microcrystalline lipase

• Reaction kinetics on palmitic acid esterification by CL-PCMC-LIP/Gly was studied.
• Effects of reaction parameters on the enzyme catalyzed reaction were studied.
• A maximum FAME yield of over 95% was achieved.
• Vmax and Km were determined by Ping-Pong bi-bi model with methanol inhibition.
• High Ki of CL-PCMC-LIP/Gly suggested high tolerance to methanol inhibition.

Enzymatic esterification of fatty acid-rich feedstocks represents an efficient and eco-friendly catalytic process for production of biodiesel. In this study, the reaction kinetics on esterification of palmitic acid with methanol using the heterogeneous glycine-based crosslinked protein coated microcrystalline lipase (CL-PCMC-LIP/Gly) was studied. The maximum FAME yield of over 95% based on a molar basis was achieved at 15% (w/w) enzyme dosage with a 4:1 [MeOH]/[FFA] molar ratio after incubation at 50 °C for 1 h in the presence of tert-butanol as a co-solvent. According to the rate equation based on the Ping Pong Bi Bi mechanism model with methanol inhibition, the maximum velocity of the reaction was 4.8 × 10−3 M/min while the Michaelis–Menten’s constants for palmitic acid (Km,PA) and methanol (Km,MeOH) were 2.2 M and 1.4 M, respectively with the inhibition constant of methanol (Ki,MeOH) of 32.6 M. The turnover number (kcat) of CL-PCMC-LIP/Gly was 2.7 min−1 under the optimized experimental condition. The reaction kinetics result provides an important basis for further up-scaling study of the enzymatic esterification process for biodiesel synthesis.