Influence of activation on the multipoint immobilization of penicillin G acylase on macroporous silica

Penicillin G acylase is the second most important: enzyme used by industry in an immobilized form. Penicillin hydrolysis is its main application. This reaction is used to produce 6-aminopenicillanic acid (6-APA), an intermedi ate in the synthesis of semisynthetic antibiotics. This work aims to compar e catalytic properties of different penicillin G acylase (PGA) derivatives obtained by multipoint immobilization of the enzyme on macroporous silica. Enzyme amino groups react with different aldehyde groups produced in the su pport using either glutaraldehyde or glyoxyl activation. In the former meth od, silica reacts with gamma-aminopropyltriethoxysilane (gamma-APTS) and gl utaraldehyde; in the latter, a reaction with glycidoxypropyltrimethoxysilan e (GPTMS) is followed by acid hydrolysis and oxidation using sodium perioda te. This work determines the influence of degree of activation, using gluta raldehyde, on immobilization parameters. PGA was immobilized on these two d ifferent supports. Maximum enzyme load, immobilized enzyme activity (deriva tive activity), rate of immobilization and thermal stability were checked f or both cases. For glutaraldehyde activation, the results showed that 0.5% of the gamma-APTS is sufficient for all the hydroxyl groups in the silica t o react. They also showed that degree of activation only affects immobiliza tion yield and reaction velocity and that reduction of the glutaraldehyde d erivatives with sodium borohydride does not affect their thermal stability. ;in comparing the derivatives obtained using glyoxyl and glutaraldehyde act ivation, it was observed that the glyoxyl derivatives presented better immo bilization parameters, with a maximum enzyme load of 264 IU/g silica and a half-life of 20 minutes at 60 degrees C.