Radioactive penicillin G production by immobilized fungal vesicles

Summary Radioactive penicillin G production from l-1-¹⁴C]-valine (1.75 GBq · mmol^-1) by native and by calcium alginate gel immobilized mycelium of Penicillium chrysogenum PQ-96 in a medium for antibiotic production as well as by vesicles isolated from the protoplasts of the same strain in a well-defined reaction mixture was investigated. Specific radioactivity of the penicillin G produced by the native vesicles was 1.45 GBq · mmol^-1 and that of the antibiotic synthesized by the calcium alginate gel immobilized vesicles was 1.48 GBq · mmol^-1. By comparison, the specific radioactivity of penicillin G produced by native mycelium was 0.42 GBq · mmol^-1 and of that synthesized by the immobilized mycelium was 0.96 GBq · mmol^-1. Production of radioactive penicillin G by native and immobilized vesicles in repeated use was also investigated. At the beginning of the production phase, the radioactive penicillin G synthesized by the immobilized vesicles was 25 nmol · mg protein^-1 · h^-1 and decreased after 8 days to a level of 11 nmol · mg protein^-1 · h^-1. The half-life of the immobilized vesicles was 7 days. The native vesicles showed a rapid decrease in radioactive antibiotic production. In comparison, the penicillin G production in a repeated use of immobilized vesicles decreased during 40 days from 140 nmol · mg protein^-1 · h^-1 to 60 nmol · mg protein^-1 · h^-1. The half-life of the immobilized vesicles was 35 days. The native vesicles showed after 4 days a lack of activity of penicillin G production. The stability of immobilized mycelium or vesicles in the process of radioactive penicillin G production is discussed.