Enhanced Antimicrobial Activity and Cytotoxicity of Egyptian Streptomyces rochei RS2 through Optimized Fermentation Conditions: Insights from MTT Assay

Abstract

Background: The escalating prevalence of drug resistance and cancer necessitates the development of novel antimicrobial and anticancer agents. Objective: This study focuses on the isolation, characterization, and bioactivity assessment of actinomycetes-derived compounds with antimicrobial and cytotoxic potential. Methodology: Fifty-five soil samples from diverse regions in Egypt were initially identified based on morphological characteristics and the VITEK® 2 system. Three isolates were further confirmed using PCR and sequencing Results: Among these, three isolates (RS1, RS2, RS3) exhibited significant antimicrobial activity. Molecular characterization via PCR amplification and phylogenetic analysis confirmed RS2 as closely related to Streptomyces rochei. Optimization of fermentation conditions (pH 7, 28–31°C, 5–7 days incubation) significantly enhanced bioactive compound production. LC-MS analysis of RS2 crude extract identified antimicrobial compounds (Candicidin, Novobiocin, Erythromycin, Chloramphenicol) and anticancer agents (Mithramycin, anthracycline). The extract demonstrated robust antibacterial activity, with inhibition zones of 19 mm (E. coli), 21 mm (B. subtilis), 14 mm (S. aureus), and 12 mm (Pseudomonas sp.). Cytotoxicity assays revealed dose-dependent inhibition of HepG2 liver carcinoma cells, with an IC50 of 79.91 ± 0.24 µg/mL and 97.46% inhibition at 1000 µg/mL. Morphological changes in HepG2 cells indicated apoptosis induction at higherconcentrations. Conclusion: These findings underscore Streptomyces rochei RS2 as a promising source of novel antimicrobial and anticancer compounds, highlighting its potential for addressing drug-resistant pathogens and cancer therapy.