Isolation, optimization, and bioactivity evaluation of Streptomyces qinglanensis VITABS23 from mangrove sediments: an...

Mangroves are valuable ecosystems that harbor unique actinobacteria capable of producing bioactive compounds of therapeutic importance. In the present study, a total of 26 marine actinobacteria were isolated using actinomycetes isolation agar and starch casein agar and were preliminarily identified as Streptomyces sp. based on colony morphology. Screening of cell-free extracts revealed that four isolates (ABS13, ABS15, ABS19 and ABS23) exhibited antibacterial activity against the tested bacterial pathogens, with isolate ABS23 showing the highest activity, producing inhibition zones of 25.0 ± 0.0 mm against Pseudomonas aeruginosa and Bacillus cereus. The extract of ABS23 also demonstrated strong antioxidant potential, as indicated by 2,2-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging (88.5 ± 0.52%) and metal chelating activity (57.38 ± 0.27%). Media optimization studies showed that sucrose and casein were the most effective carbon and nitrogen sources for enhanced metabolite production. GC-MS analysis revealed the presence of several bioactive compounds, including heterocyclic compounds, esters and pyrrolopyrazines. In silico analysis using SwissADME and pKCSM predicted favorable drug-likeness and pharmacokinetic properties of the identified metabolites. Furthermore, the potential isolate was identified as Streptomyces qinglanensis VITABS23 by 16S rRNA sequencing. Overall, this study highlights actinobacteria derived from mangrove sediments are potential sources of lead compounds for pharmaceutical applications.