Desenvolvimento de biocatalisadores à base de lipase B de Candida antarctica imobilizada em poli(estireno-co-divinilbenzeno) magnético para aplicação em reações de esterificação

Abstract

Magnetic biocatalysts combine magnetic properties with the catalytic activity of enzymes, which enables the development of biocatalysts that are easy to recover and reuse in esterification reactions of industrial relevance. In this Dissertation, poly(styrene-co-divinylbenzene) copolymers containing magnetite were synthesized by polymerization in aqueous semisuspension. These copolymers were used as supports for the immobilization of Candida antarctica lipase B (CALB). Different dilutions in n-heptane (S1 = 50%, S2 = 100% and S3 = 150%) were used in the synthesis of these particles, in order to vary the structure of the magnetic support and to study the relationship between the morphology of the supports and the immobilization parameters and the performance of the biocatalysts. The obtained magnetic supports were characterized by optical microscopy, FTIR, TG-DTG, SEM-EDS, XRD, ASAP and VSM. The support prepared with 100% dilution in n-heptane (S2) was the only one obtained with spherical morphology and particle integrity. The immobilization kinetics were monitored by means of the hydrolytic activity (U/mL) and the protein concentration (mg/gsupport) in the supernatant. It was not possible to observe any variation in the immobilization yield of the biocatalysts as a function of the variation in the degree of dilution. The magnetic biocatalysts obtained (BioS1, BioS2 and BioS3) presented ethyl oleate conversions of 30,5±6,0; 63,0±10,8 and 66,0±5,2%, respectively. Studies evaluating the influence of temperature and the influence of the carbon chain size of fatty acids on esterification were conducted with the BioS2 biocatalyst, obtained from the S2 support, with better structural integrity. BioS2 presented higher ethyl oleate conversion percentages at all temperatures evaluated (30, 40, 50 and 60 °C), compared to free CALB, showing that the support conferred greater thermal stability to the enzymes. The biocatalyst BioS2 showed higher conversions than free CALB in the esterification reactions of palmitic, stearic and oleic acids. However, the percentage of conversion into ester in the esterification reaction of capric acid was higher for free CALB. These results suggest that immobilization favored the conversion into esters of fatty acids with larger chain sizes, compared to free CALB. Five cycles of use of the magnetic biocatalyst BioS2 were conducted, which maintained 50% of the initial ethyl oleate conversion percentage. It can be stated that a new magnetic biocatalyst was obtained based on CALB immobilized in magnetic poly(styrene-co-divinylbenzene) and demonstrated to be suitable for esterification reactions of ethyl esters from aliphatic fatty acids with different carbon chain lengths.