CONTROL OF THE PRODUCTION OF INDIVIDUAL FUSICOCCINS AT DIFFERENT DISSOLVED-OXYGEN CONCENTRATIONS

The regulatory effect of different concentrations of dissolved oxygen on the production of fusicoccins by the fungus Del. was studied. The m aximum output of total fusicoccins was obtained by using a profiled Fu sicoccum amygdali dissolved oxygen tension (DOT) regime, in which the DOT was maintained at 15-20% during the biomass growth phase and at 5- 8% during the fusicoccins production phase. In comparison with the pro filed regime, the maintenance of DOT at 15-20% during the whole fermen tation shortened the fusicoccins production phase. The fermentation pe rformance at a low DOT (5-8%) inhibited both the accumulation of bioma ss and the production of fusicoccins. At high DOT (40-50%), an acceler ated accumulation of the biomass with an expressed autolysis of myceli a took place, and the production of fusicoccins was lowered. The quali tative composition of individual fusicoccins varied substantially at d ifferent DOTs. Fusicoccins, A, C, D, J, H, 16-O-demethyl-J, detretpent enylfusicoccin and some minor fusicoccin metabolites were found in the fermentation broth using the method of liquid secondary ion mass spec trometry. It was established that the profiled DOT regime (15-20% to 5 -8%) provided both the maximum concentration of fusicoccins and an enh anced accumulation of the main metabolite - fusicoccin A (FC A). The p erformance of the fermentation at a DOT of 15-20% decreased the conten t of FC A by 2-6% in comparison with the profiled DOT regime, and incr eased the content of fusicoccin C to 14-20% of the total fusicoccins. Fermentation at DOT of 5-8% was characterized by the highest content o f the precursors of FC A, the less oxidized fusicoccins H and J, the c ontents of which were in range 7-12% and 16-17% of total fusicoccins, respectively.