Synthesis and optimization of biocatalysts for the kinetic resolution of (R,S)-ibuprofen.

LLERENA-SUSTER, C.R.; MORCELLE, S.R.; BRIAND, L.E.

Workshop; VII workshop on biocatalysis and biotransformations-1º simposio latinoamericano de biocatálisis y biotransformaciones; 2014

Protein immobilization assays were performed with solutions containing various concentrations of the crude extract (0.5 mg/ml towards 1.5 mg/ml) of the lipase B of Candida antarctica (Lipozyme® LCN02102). The amount of protein before and after the adsorption on titanium oxide (P-25, Evonik Industries, 43.1 m2/g) was determined through the Bradford assay. The adsorption isotherms demonstrated that the dispersion limit is 10.8 +/- 0.5 mg of protein per 100 mg of TiO2. The esterification of racemic ibuprofen (0.12 M) with a stoichiometric amount of ethanol in an isooctane mixture was performed at 45 oC with 20 mg of 11 % CALB/TiO2. Surprisingly, the conversion to ethyl esters and enantiomeric excess towards the S(+)-ibuprofen showed variations from 15 % (eeS = 6.5 ) to 63 % (eeS = 56) at 24 hs of reaction. In fact, the higher the protein concentration of the starting solution used in synthesis of the biocatalyst the higher the catalytic performance although the amount of dispersed protein on the oxide support was similar. This observation clearly demonstrated that other components of the crude extract co-adsorb with the protein and somehow promote the catalytic activity. Further experiments demonstrated that the addition of a mixture of sorbitol (25% w/w) and glycerol (25%w/w) improved the catalytic activity of the titania supported CALB reaching a maximum when the volume of the added mixture was about three times the volume of the crude extract. The biocatalyst 11 % CALB/TiO2 synthesized with a crude extract containing 11.2 mg/ml of protein and the addition of 1.20 ml and 2.40 ml of the sorbitol glycerol mixture showed 43.2 (eeS = 30) % and 52.0 (eeS = 41) % of conversion at 24 hs of reaction, respectively. Those conversions of racemic ibuprofen represent an improvement of 53 % and 84 % compared with the conversion (28.2 % (eeS = 19) of the profen obtained with the same material with the addition of the promoters.