A POSTFERMENTATIVE STAGE IMPROVES PENICILLIN ACYLASE PRODUCTION BY A RECOMBINANT ESCHERICHIA-COLI

Active penicillin acylase is formed only after an in vivo post-transla tional processing of the polypeptide precursor. Such a maturation proc ess is rare in procaryotes. In this work, incubation under aerated con ditions, of whole recombinant E. coli cells after glucose depletion an d growth cessation, i.e., during the postfermentative stage, consisten tly resulted in 2- to 4-fold increases in penicillin acylase activity. Such results suggest that penicillin acylase maturation occurs to a h igh extent even during the postfermentative stage. Accordingly, the ef fect of different incubation conditions, during the postfermentative s tage, on penicillin acylase was determined. incubation under anaerobic conditions resulted only in a 1.27-fold increase of enzyme activity, with respect to the end of the batch culture, whereas a 3- and 4-fold increase occurred during incubation under dissolved oxygen concentrati ons of 100 and 43% (with respect to air sat.), respectively. Only a sm all negative effect on the maturation process, was observed during inc ubation with acetate concentrations above 0.6 g/L. No effect of pH, in the range of 6.0 to 8.0, was observed.