Effect of compressed fluids treatment on β-galactosidase activity and stability.

This study aimed at assessing the influence of different pressurized fluids treatment on the enzymatic activity and stability of a lyophilized β-galactosidase. The effects of system pressure, exposure time and depressurization rate, using propane, n-butane, carbon dioxide and liquefied petroleum gas on the enzymatic activity were evaluated. The β-galactosidase activity changed significantly depending on the experimental conditions investigated, allowing the selection of the proper compressed fluid for advantageous application of this biocatalyst in enzymatic reactions. The residual activity ranged from 32.1 to 93.8 % after treatment. The storage stability of the enzyme after high-pressure pre-treatment was also monitored, and results showed that the biocatalyst activity presents strong dependence of the fluid used in the pretreatment. The activity gradually decreases over the time for the enzyme treated with LGP and propane, while the enzyme treated with n-butane maintained 96 % of its initial activity until 120 days. For CO(2), there was a reduction of around 40 % in the initial activity 90 days of storage. The enzyme treated with n-butane also showed a better thermostability in terms of enzymatic half-life.