Advantages of using non-isothermal bioreactors for the enzymatic synthesis of antibiotics: the penicillin G acylase as enzyme model

A new hydrophobic and catalytic membrane was prepared by immobilizing Penicillin G acylase (PGA, EC.3.5.1.11) from E. coli on a nylon membrane, chemically grafted with butylmethacrylate (BMA). Hexamethyldiamine (HMDA) and glutaraldehyde (Glu) were used as a spacer and coupling agent, respectively. PGA was used for the enzymatic synthesis of cephalexin, using D(-)-phenylglycine methyl ester (PGME) and 7-amino-3-deacetoxycephalosporanic acid (7-ADCA) as substrates. Cephalexin production was studied in a bioreactor operating under non-isothermal conditions, and was found to linearly increase with the applied temperature gradient. A temperature difference of about 3 °C across the catalytic membrane resulted into a cephalexin synthesis increase of 100 % with a 50 % reduction of the production times. The efficiency of the system was also determined at various concentrations of the two substrates, by calculating the a* coefficients, which represent the percentage increase of enzyme activity when a unit temperature difference is applied across the catalytic membrane. An equation relating the percentage reduction of the production times to the percentage activity increases was also determined. The membrane was also physically characterized, by estimating its hydrophobicity through the values of the hydraulic and thermoosmotic permeability coefficients. The advantage of using non-isothermal bioreactors in biotechnological processes, including pharmaceutical applications, is also discussed