Optimizing Production Conditions of a Caspian Sea <i>Actinomycete</i> 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. <i>Streptomyces</i> 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 <i>Staphylococcus aureus</i> and <i>Enterococcus faecalis</i> 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 <i>Staphylococcus aureus</i> and <i>Enterococcus faecalis</i> 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.