A kinetic study of starch palmitate synthesis by immobilized lipase-catalyzed esterification in solvent free system

• Lipase-catalyzed esterification of starch with oleic acid in solvent-free system.
• Propose a reaction mechanism and to develop a rate equation.
• Obey the Ping-Pong bi-bi mechanism.
• The kinetic equation was v = (1.735 × Cfatty-acid × Cstarch)/(Cfatty-acid × Cstarch + 0.0156 × Cstarch + 2.3947 × Cfatty-acid).
• The obtained kinetic equation, initial reaction rates were successfully predicted for initial pretreatment starch quantity below 10 mmol.

The objective of this work was to propose a reaction mechanism and to develop a rate equation for the synthesis of starch palmitate by acylation of the corn starch with palmitic acid using the lipase Novozym 435 in solvent-free system. Initial rate data and progress curve data were used to arrive at a suitable model. The initial rate studies showed that the kinetics obey the Ping-Pong bi-bi mechanism. An attempt to obtain the best fit of this kinetic model through computer simulation yielded in good approximation, the kinetic equation was v = (1.735 × Cfatty-acid × Cstarch)/(Cfatty-acid × Cstarch + 0.0156 × Cstarch + 2.3947 × Cfatty-acid). The mathematical expressions have been tested using several sets of data obtained from reactions carried out under different reaction conditions. The predicted values provide very good fits of the experimental data for the molar of starch from 2 mmol to 10 mmol, the molar of palmitic acid from 5 mmol to 70 mmol, the reaction temperature from 50 °C to 70 °C, amount of lipase from 44 mg to176 mg, rotate speed from 100 r/min to 240 r/min, initial aw from <0.01 to 0.57.

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