Lipase-catalyzed transesterification of krill oil and 3,4-dihydroxyphenyl acetic acid in solvent-free medium using response surface methodology

Abstract

The optimization of the enzymatic transesterification in solvent-free medium (SFM) of krill oil with selected phenolic acids (PAs), using two immobilized lipases, was investigated. The use of Novozym 435 with 3,4-dihydroxyphenylacetic acid resulted in the highest bioconversion yield (BY). The central composite rotatable design was used to evaluate the effects of the PA concentration (PAC) and lipase concentration (LC) as well as the agitation speed (AS) on the BY of phenolic lipids. The initial findings indicated that the stationary point was a saddle point. To overcome this saddle point, sequential experiments have been carried out at fixed PAC, with LC and AS as the two independent variables. For the models with PAC, fixed at 10 and 20 mM, the results revealed that LC had a significant quadratic effect (P < 0.05) on the %BY, whereas a significant linear effect was only obtained at PAC fixed at 20 mM. The AS had a significant quadratic effect (P < 0.05) on the %BY only for the model with PAC fixed at 10 mM. At fixed PAC of 20 mM, the response surface model predicted a BY of 75%, using a LC of 62 mg/mL and an AS of 154 rpm. The subsequent verification experiment carried out under these conditions confirmed the validity of the prediction.