Deciphering the roles of fatty acids and oils in fungichromin enhancement from Streptomyces padanus

Fungichromin (FC), a polyene macrolide antibiotic, was found to be useful in the treatment of resistance for plant diseases such as Rhizoctonia damping-off of cabbage and tomato late blight. A novel strain, Streptomyces padanus PMS-702, was employed to study the cultivation conditions for FC production. When using linoleic acid as an additive, a negative effect on FC production was observed. On the contrary, when using oleic acid in concentration of 0.01 M (2.82 g/L), a 3.5-fold enhancement of FC production with a slight increase in cell biomass was obtained. To study the effects of plant oils, various plant oils were used as additives. It was found that all the plant oils (namely, corn oil, olive oil and etc.) promote FC production up to about 4.9-fold as compared to that without such an addition. A quantitative analysis on FC yield indicated that, at a lower concentration, fatty acids and plant oils play roles as both a stimulator and a carbon source whereas, at a higher concentration, they serve mainly as the carbon source. This morphological study showed that the addition of fatty acids and oils in the medium vary the cell membrane permeability. The fact that FC could be rapidly secreted out into the medium after its synthesis as well as its stimulatory effect attributed to a dramatic increase in FC production