Improved oxygen transfer in cultures of Nocardia lactamdurans maintains the cephamycin biosynthetic proteins for prolonged time and enhances the conversion of deacetylcephalosporin into cephamycin C

Abstract

Batch cultures of Nocardia lactamdurans MA4213 in stirred tank fermentors (400 rpm) became oxygen limited after 45 h of incubation. When the stirrer speed was increased at 36 h from 400 to 600 rpm there was a 5-fold increase in the dissolved oxygen (DO) in the broth what resulted in a 2-fold stimulation of cephamycin biosynthesis. Immunoblotting studies using antibodies against the α-aminoadipyl-cysteinyl-valine synthetase and the protein P7 (cephem-7-hydroxylase) component of the methoxylation system showed that cultures with increased DO concentrations maintained high levels of these proteins for an extended period of time. Under these conditions there was an enhanced conversion of cephamycin intermediates into cephamycin C. Allophane and alumina exerted a strong stimulatory effect on cephamycin biosynthesis that correlated with high DO levels in allophane- or alumina-supplemented cultures at low agitation speeds. Allophane or alumina supplementation of N. lactamdurans cultures resulted in a delayed decay of the cephem-7-hydroxylase protein in the cells favoring conversion of the cephamycin intermediates into cephamycin C.