Optimizing Production Conditions of a Caspian Sea Actinomycete Exhibiting Promising Antibacterial Activity Against Clinically-important Pathogens Using the Two-Factor Interaction/ Minimum Run Resolution IV Method.

Natural products recovered from marine sediment have the potential for the treatment of various diseases. Streptomyces sp., strain MN38 which was previously isolated from the Caspian Sea of Iran was at first characterized based on its 16srRNA analysis and morphological properties. Two-factor Interaction/ Minimum Run Resolution IV method was employed to evaluate the influence of various potential factors on the strain's antibacterial activity using cost-effective substrates. Twelve variables were considered effective for investigation, with an emphasis on assessing the antibacterial activity against Staphylococcus aureus and Enterococcus faecalis via the micro-dilution method. The findings indicate that a quadratic model and a second-order polynomial equation are statistically significant at the 95% confidence level due to a low P-value (< 0.0001) in this context. As a result, A1BFe+C agar medium, incubated at 28°C for three days with a shaking speed of 200 rpm, using specific concentrations of starch (5.0 g/l), yeast extract (6.0 g/l), peptone (4.0 g/l), KBr (0.5 g/l), CaCO₃ (0.2 g/l), sea salt (15 g/l), and Fe₂(SO₄)₃ (0.003 g/l), along with an inoculum size of 3.0% v/v at a pH of 6, exhibits the enhanced antibacterial activity against Staphylococcus aureus and Enterococcus faecalis reached up to 69 and 166 (Bu/ml). It could be concluded that the MN38 of Caspian Sea sediments was a potent source of antimicrobial agent production and the production process was significantly optimized using mathematical methods.