Optimization of the parameters that affect the synthesis of magnetic copolymer styrene-divinilbezene to be used as efficient matrix for immobilizing lipases

摘要

The parameters that effect the synthesis of poly(styrene-co-divinylbenzene) magnetized with magnetite (STY-DVB-M) by polymerization emulsion were assessed in order to obtain magnetic beads to be used as matrix for lipase immobilization. The combined effect of polyvinyl alcohol (PVA) concentration and agitation was studied using response surface methodology. A 2(2) full-factorial design was employed for experimental design and analysis of the results. The optimum PVA concentration and agitation were found to be 1wt% and 400rpm, respectively. These conditions allow attaining the best particle size distribution of the synthesized particles (80% between 80 and 24 mesh). The performance of the magnetic beads was tested as a matrix for immobilizing two microbial lipases (Lipases from Burkholderia cepacia-BCL and Pseudomonas fluorescens-AKL) by physical adsorption and high immobilization yields (&70%) and hydrolytic activities (1850Ug(-1)) were attained. The properties of free and immobilized lipases were searched and compared. Similar performance regarding the analyzed parameters (biochemical properties, kinetic constants and thermal stability) were obtained. Moreover, both immobilized lipases were found to be able to catalyze the transesterification of coconut oil with ethanol to produce fatty acid ethyl esters (FAEE). Further study showed that the B. cepacia immobilized lipase could be used seven times without significant decrease of activity, revealing half-life time of 970h.