Investigation of the causes of deactivation–degradation of the commercial biocatalyst Novozym® 435 in ethanol and ethanol–aqueous media

The effect of contacting neat ethanol and an ethanol: H2O mixture on Novozym® 435 was investigated at room temperature and 45 °C, during various periods of time of interaction with the alcohol (from 40 min to 8 days) and at different biocatalyst: ethanol (ethanol/water) ratios. The alcohol dissolves the polymethylmethacrylate (PMMA) that constitutes the support of the Candida antarctica B lipase (CALB) regardless of the conditions investigated and diffuses into the biocatalystʹs beads remaining strongly adsorbed (the desorption of the alcohol is evidenced only upon heating at 150 °C). The diffusion of the alcohol alters the inner texture of the beads generating channels and increasing the roughness of the polymeric material. Additionally, the ethanol (with or without water added) modifies the secondary structure of the enzyme by decreasing the α-helix contributions and increasing the β-sheet structure.