Comparative study of fatty acids composition during cortexolone hydroxylation and tributyltin chloride (TBT) degradation in the filamentous fungus Cunninghamella elegans

Abstract

The filamentous fungus Cunninghamella elegans IM 1785/21Gp is able to metabolize and detoxify numerous structurally different hydrophobic chemicals, among them previously examined by us tributyltin (TBT) and cortexolone. In the present work parallel detoxification of both substrates and changes in the fungus membrane fatty acids were studied. TBT dealkylation rate in the presence of corticosteroid was lower as compared to the control culture without corticosteroid (92% and 70% after 5 days of incubation, respectively). Cortexolone hydroxylation was also inhibited in the presence of the organotin substrate (97% and 80% after 3 days of incubation, respectively). Fatty acids examination disclosed C16:0, C18:1, C18:2, C18:3, C18:0 as major components of glycolipids, phospholipids and neutral lipids of the fungus. In the presence of TBT (5 mg l−1) a significant increase in the fatty acid saturation index was noticed. The formation of oleic acid (C18:1) by C. elegans IM 1785/21Gp in the presence of butyltin was markedly reduced, suggesting that TBT inhibited Δ9 stearoyl-CoA desaturase (SCD) activity. In contrast, cortexolone (250 mg l−1) decreased the ratio of fatty acids saturation and stimulated SCD activity. In the cultures with both toxic substrates TBT inhibition of desaturase was partly suppressed by cortexolone. This phenomenon was associated to a significant limitation of fungal growth. The remarkable detoxification ability of C. elegans IM 1785/21Gp is attributed to the presence of a diversity of mechanisms of hydrophobic compounds detoxification in this fungus.