ESTERIFICATION OF R/S-KETOPROFEN WITH 2-PROPANOL AS REACTANT AND SOLVENT

MARÍA VICTORIA TOLEDO; CARLA JOSÉ; SEBASTIÁN E. COLLINS; RITA BONETTO; MARÍA LUJÁN FERREIRA; LAURA E BRIAND

JOURNAL OF MOLECULAR CATALYSIS B-ENZYMATIC

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2012 vol. 83 p. 108 - 119

1381-1177

The enzymatic esterification of R/S-ketoprofen with 2-propanol catalyzed with the commercial biocatalyst Novozym® 435 is addressed in this investigation. The low reaction rate registered in this reaction was investigated in terms of the effect of the alcohol on the physicochemical-enzymatic stability of the biocatalyst and the interaction of the substrates with the catalytic triad at a molecular level. The effect of contacting 2-propanol: H2O mixture on Novozym® 435 was investigated at 45 oC for an extended period of time (8 days). The mixture dissolves the polymethylmethacrylate (PMMA) that constitutes the support of the Candida antarctica B lipase (CALB). Additionally, the alcohol diffuses into the biocatalyst´s beads remaining strongly adsorbed (the alcohol desorption is evidenced only upon heating at 187 oC) and altering the inner texture of the biocatalyst´s beads. Additionally, 2-propanol modifies the secondary structure of the enzyme by decreasing the b-sheet contribution and increasing the b-turn structure. The molecular modeling of the interaction of R/S-ketoprofen and 2-propanol with the catalytic triad of the lipase provides evidences that the secondary alcohol exerts an important steric hindrance for the reaction to proceed.