Preparation of crosslinked enzyme aggregates (CLEA) of catalase and its characterization

In this study, bovine liver catalase was immobilized as crosslinked catalase aggregates via precipitation with ammonium sulfate and then crosslinking with glutaraldehyde. The immobilization conditions of crosslinked catalase aggregates (CLEA-CAT) were determined in terms of ammonium sulfate concentration (w/v), glutaraldehyde concentration (mM), crosslinking time (h) and immobilization pH and their optimal values were determined as 70% (w/v), 140 mM, 6 h and 7.0, respectively. The effect of bovine serum albumin (BSA) as feeder protein on the activity of CLEA-CAT was also investigated at different catalase + BSA combinations and the highest activity of the CLEA-CAT prepared in the presence BSA (CLEA-CAT-BSA derivative) was observed for 10 mg/mL catalase + 10 mg/mL BSA combination. The optimal working conditions of free catalase were determined as pH 7.5, buffer concentration 50 mM and temperature 25 °C. The corresponding working conditions were 7.5, 75 mM and 35 °C, respectively for CLEA-CAT-BSA derivative. The catalytic efficiency (kcat/Km) values were estimated as 1.6 × 106 s−1 M−1 for the free catalase and 3.8 × 103 s−1 M−1 for the CLEA-CAT-BSA derivative. Thermal and storage stabilities of CLEA-CAT-BSA derivative were better than those of the free catalase and the remaining activity of CLEA-CAT-BSA derivative was 50% of its initial activity at the end of 400 consecutive uses in a batch type reactor.