Kinetics of lipase-catalyzed de-acidification of degummed rapeseed oil utilizing monoacylglycerol as acyl-group acceptor

• Kinetics of enzymatic de-acidification of degummed rapeseed oil was studied.
• Esterification reaction follows a multi-substrate Ping Pong mechanism.
• Kinetic parameters indicate competitive lipase inhibition by the acyl-group acceptors.
• Free fatty acids do not affect lipase activity within the ranges investigated.

Due to an increasing awareness on ecological process management the substitution of conventional processes for the de-acidification of vegetable oils has been focused by research, recently. The present study examines the mechanism of enzymatic de-acidification in degummed rapeseed oil by esterification of free fatty acids with an acyl-group acceptor (monoacylglycerol) utilizing an immobilized lipase from Rhizomucor miehei. As the experiments were performed in a solvent free system, first investigations comprise the exclusion of possible mass transfer limitations. The results obtained for the kinetically controlled system strongly indicate that the reaction seems to follow a multi-substrate Ping Pong mechanism. A slight competitive inhibition of the reaction by the acyl-group acceptors was observed during the determination of the effect of substrate concentration on lipase-catalyzed esterification. The free fatty acid content did not influence the activity of the biocatalyst within the ranges investigated. The kinetic parameters were determined, exhibiting that the lipase has a higher affinity towards the acyl-group acceptors (K(AGA) = 150 mM) than to free fatty acids (K(AGD) = 204 mM). The maximum reaction rate for the present reaction system was evaluated to be 41.3 U/g protein.

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