Preparation of cross-linked aggregates of aminoacylase from Aspergillus melleus by using bovine serum albumin as an inert additive

The effects of bovine serum albumin (BSA) addition on the cross-linked enzyme aggregates (CLEA) of aminoacylase from Aspergillus melleus (EC 3.5.1.14) were conducted at varying glutaraldehyde to enzyme ratio. After optimization, CLEA of aminoacylase prepared with 10 mg BSA per 100 mg enzyme retained 82% activity recovery (named CLEA-E-BSA) whereas CLEA prepared without BSA retained only 24% activity recovery (named CLEA-E) due to the low content of amine residues of aminoacylase. Compared with free aminoacylase, the catalytic performance of CLEA-E-BSA (kcat/Km) decreased from 0.357 to 0.270, while the thermal stability of CLEA-E-BSA has improved considerably, maintaining 52% residual activity after 24 h of incubation at 47 °C whereas the free enzyme was almost inactivated. Additionally, the inactive curve of CLEA-E-BSA fitted a two-exponential deactivation model. The reusability of CLEA-E-BSA with respect to N-acetyl-dl-methionine hydrolysis was evaluated. CLEA-E-BSA showed 82.4% residual activity even after 10 cycles of repeated use.