Effects of Different Elicitors on Terpene Production and Biological Activities of <i>Streptomyces</i> sp. <scp>PT6</scp>

ABSTRACT Streptomyces is recognised for its capability to produce a diverse array of secondary metabolites characterised by unique structures and a wide range of biological activities. However, the production of these secondary metabolites often diminished when cultivated under laboratory conditions. In this study, various elicitors were used to enhance or induce secondary metabolites of Streptomyces sp. PT6 and their effects were evaluated for antimicrobial and cytotoxic activities as well as the secondary metabolite profiles using TLC, GC–MS and LC–MS–MS. ISP2 CuSO 4 extract was prepared by cultivating Streptomyces sp. PT6 in ISP2 supplemented with CuSO 4 • 5H 2 O; 3 μM exhibited the best antimicrobial and cytotoxic activities. Each extract showed different secondary metabolite profiles using two different GC–MS methods. Method 1 successfully identified various terpenes, including 3‐carene, p ‐cymene D‐limonene and linalool, but method 2 failed to detect these terpenes. The presence of D‐limonene and linalool in 4 extracts (ISP2, ISP2 CuSO 4 , ISP2 catechol and ISP2 quercetin) was confirmed through comparison with standard solutions. Several nodes from the GC–MS datasets and all nodes from the LC–MS–MS dataset remained unidentified based on untargeted metabolomic analysis, indicating the presence of potentially novel compounds. These findings indicate that Streptomyces sp. PT6 has the potential to produce antimicrobial, cytotoxic, flavour or fragrance compounds.