Residual fructose and osmolality affect the levels of pneumocandins B-o and C-o produced by Glarea lozoyensis

A high total pneumocandin titer (B-0 + C-0) with a low percentage of the st ructural isomer pneumocandin C-0 was achieved by carrying out fermentations of Glarea lozoyensis at a high residual fructose concentration (125 g/l in itial). When the fermentation was carried out at a low residual fructose co ncentration (40 g/l initial), pneumocandin production increased by 34%. How ever, a disproportionate increase in the level of pneumocandin C-0 synthesi zed (250% increase vs 30% increase for pneumocandin B-0) was observed. Midc ycle addition of 150 mM NaCl or 116 mM Na2SO4 to low residual fructose ferm entations returned the titer and isomer levels to those seen for the high r esidual fructose fermentation. The increase in pneumocandin C-0 synthesis u nder low residual fructose conditions appears to be linked to the increase in the synthesis of trans-4 hydroxyproline, with the synthesis of trans-3 h ydroxyproline remaining unaffected. This suggests that the formation of pne umocandin C-0 is the result of a misincorporation of trans-4 hydroxyproline instead of trans-3 hydroxyproline by the pneumocandin peptide synthetase, and that the amount of trans-4 hydroxyproline formed dictates the frequency of this misincorporation.