Enhancement of daptomycin production in Streptomyces roseosporus LC-51 by manipulation of cofactors concentration in the fermentation culture

Abstract

The effects of eight cofactors of enzymes on daptomycin production were investigated in this work, which included nicotinic acid (VPP), riboflavin (VB₂), heme, thiamine (VB₁), biotin (VH), cyanocobalamin (VB₁₂), tetrahydrofolic acid (THF) and pyridoxal 5-phosphate (VB₆). The dry cell weight (DCW), consumption of glucose, and daptomycin production were obviously improved when proper amount of exogenous cofactors were supplemented in the medium. The effects of heme, THF, VB₁₂ and VB₆ on daptomycin production were especially notable. The daptomycin yield enhanced 363, 104, 53 and 46%, respectively, when optimized amount of these four cofactors were supplemented in the broth. Moreover, the daptomycin yield further increased to 632 mg/l, which was over 4.5-fold higher than that of the control (without cofactors), at 132 h in a 7.5-l fermenter, by supplementation all of the eight cofactors at optimized concentrations (VPP 4 mg/l, VB₂ 0.5 mg/l, heme 9 mg/l, VB₁ 0.4 mg/l, VH 0.1 mg/l, VB₁₂ 0.04 mg/l, THF 6 mg/l and VB₆ 0.4 mg/l). Further, the effects of cofactors on the corresponding key enzymes and important intracellular metabolites were studied in order to elucidate the mechanism of enhancement of daptomycin production by manipulation of cofactors concentration in the fermentation culture. It is suggested that this strategy for increasing the daptomycin production in Streptomyces roseosporus LC-51 by manipulation of cofactors concentration in the fermentation culture may provide an alternative approach to enhance the production of metabolites in other Streptomyces.