Stability of immobilized β-galactosidase in supercritical CO2

Abstract

The enzyme β-galactosidase was immobilized by two different methods: as cross-linked enzyme aggregates (CLEA) and as magnetic cross-linked enzyme aggregates (mCLEA). Prepared immobilized enzyme was exposed in the supercritical carbon dioxide (SC CO2) at different temperatures (50 °C and 80 °C) and at different pressures (100 bar, 200 bar and 300 bar). Activity of the immobilized enzyme was measured after each exposure to SC CO2. Activity of immobilized enzyme (CLEA and mCLEA) after lyophilization was determined as well. Also, stability of pure enzyme in SC CO2 was determined. Activity assay for β-galactosidase was performed using O-Nitrophenyl β-D-Galactoside as a substrate. Later on, the activity of immobilized and pure enzyme was defined spectrophotometrically with measuring absorbance at 405 nm. activity. Regarding to the immobilized enzymes after lyophilisation, in comparison to CLEA, the mCLEA shows better stability at storage conditions. The higher enzyme activity obtained and therefore, the optimal conditions were with using mCLEA β-galactosidase after SC CO2 treatment at 300 bar and 80 ºC.