Bioactive Compound Extraction from Diverse Actinobacteria

All twenty-five strains were pre-cultured (5 mL, 28 °C, 160 rpm for 7 days) in ISP2 medium [82 (link)], ISP3 medium [82 (link)] A1M1 medium [27 (link)] and 10-fold diluted TSB medium (BD™) prepared in distilled water. Instant ocean (18 g/L) was added in each of them. Each culture [ISP2/ISP3/A1M1/10-fold dil. TSB medium (50 mL) with activated HP-20 resin (Sigma) (2.5 g)] was inoculated (5% v/v pre-culture) and fermented (14 days, 28 °C, 160 rpm). The culture was then centrifuged (4000 rpm, 20 min), the supernatant removed, and the cell/resin pellet lyophilised until dry (Thermo Savant MicroModulyo, Thermo Fisher Scientific, Waltham, MA, USA). The lyophilised cell/resin pellet was extracted twice with ethyl acetate (Fisher Scientific, Loughborough, UK, reagent grade) (20 mL, 100 rpm, 25 °C). The extracts were combined, dried (under N₂), the weight recorded and stored (4 °C).