Abstract: 【Aim】To determine the antimicrobial activities of the fermentation products of actinomycetes from the gut of Odontotermes formosanus and analyze their antimicrobial components, so as to find novel antimicrobial lead compounds.【Methods】 The gut actinomycetes of O. formosanus were isolated by spread plate method. The antimicrobial activities of the fermentation broth extracts against four pathogens (Staphylococcus aureus, Escherichia coli, Bacillus subtilis and Candida albicans) were tested by the Oxford cup method, and the active strain BYC-18 was screened. The taxonomic status of BYC-18 was determined according to its morphological features and 16S rRNA sequence analysis. The antimicrobial activities of different polar solvent extracts of BYC-18 fermentation solution were determined by filter paper method. Active compounds were isolated and purified from ethyl acetate crude extract by various chromatographic methods, and the chemical structure of the isolated compound was identified by mass spectrometry and nuclear magnetic resonance spectroscopy. The antimicrobial activities of the isolated compound were determined by filter paper method and minimum inhibitory concentration method. 【Results】 BYC-18 was identified as a strain of Streptomyces sp. The fermentation broth of BYC-18 had antimicrobial activities against all the four pathogens, and its ethyl acetate extract had an obvious inhibitory effect on S. aureus, with an inhibition zone diameter of 11.1 mm. A monomer compound BYC-18-1 was isolated from the ethyl acetate extract and identified as β-rubromycin. The antimicrobial activity test showed that β-rubromycin had a strong inhibitory effect on S. aureus at the test concentration of 30 μg/6 mm filter paper, and its inhibition zone diameter was 13.2 mm, which was close to that of the positive gentamicin sulfate (inhibition zone diameter: 16.6 mm). 【Conclusion】The Streptomyces strain BYC-18 has the potential to be developed as a new bactericide.

Key words: Odontotermes formosanus, gut actinomycetes; Streptomyces sp., antimicrobial activity, natural product