Microbial natural products have an adaptive role as signal molecules or defense tools in ecological interactions [1]. Biosynthesis of these molecules is suppressed in standard laboratory conditions where there are no ecological triggers. Thus, only a portion of the chemical diversity of a microbial strain is discovered by standard fermentation protocols. However, using different fermentation conditions or different approaches such as co-culture, biosynthesis of these suppressed molecules can be triggered, and new natural products can be isolated [2],[3].
In our previous studies, it was demonstrated that marine derived Streptomyces cacaoi had a potent antimicrobial effect against Enterecoccus feacium and MRSA [4]. A comprehensive statistical optimization of this promising strain was aimed to enrich the chemical diversity of the ethyl acetate extract and to increase its bioactivity. Response surface methodology was used for statistical optimization of some fermentation paramaters. As responses, the chemical diversities of the ethyl acetate extracts were monitored by HPLC-DAD system, and the antimicrobial effects were determined by disc diffusion assay on Bacillus subtilis. As a result, the diameter of the inhibition zones (150 µg extract) varied between 6 to 25.5 mm against Bacillus subtilis. Also, chemical profiles of the extracts varied even in the major compounds. Consequently, this study demonstrated the importance of optimization protocols for the discovey of new/novel molecules in microbial natural product research.
