Effect of exogenous combinations of fatty acids on the production of monensin by Streptomyces cinnamonensis

Monensin is produced by the fermentation of Streptomyces cinnamonensis, which is in wide use in the agricultural and pharmaceutical industries. To improve the monensin yield, this study focused on evaluating the role of fatty acids in vegetable oil on the strain growth and secondary metabolism. Results showed that soybean oil was the most effective for monensin fermentation, followed by olive, peanut, camellia, corn, and linseed oils. Four fatty acids, oleic acid, linoleic acid, stearic acid, and palmitic acid, predominantly consisting of these vegetable oils, were observed to exert a positive effect on the monensin fermentation, thus resulting in the monensin titer increasing by 8-, 6-, 2-, and 3-fold, though far inferior to the soybean oil (10-fold). Optimization of fatty acid addition, comprising 1.38 % oleic, 2.78 % linoleic, 0.31 % stearic, and 0.50 % palmitic acid, elevated the monensin titer to 15.0 g/L. With a fed-batch fermentation in a 10-L tank, the fermentation reached 26.71 g/L of the monensin, above 10 % higher than that of the soybean oil. The suitable combination of fatty acids in vegetable oil was favorable for the microbial growth and monensin synthesis, which can shed light on the desirable application of different oil varieties in the industrial.