Screening and molecular identification of biosurfactant-producing endophytes from Quillaja lancifolia D. Don

Endophytes are widespread microorganisms that colonize plant tissues without causing apparent harm. These organisms possess diverse metabolic repertoires and can be alternatives or complementary sources of high-value bioactive compounds. Saponins stand out due to their surfactant, foaming, and immunoadjuvant properties. Triterpene saponins from Quillaja spp. are used to enhance both humoral and cellular responses in human and veterinary vaccines. Herein, screening and identification of biosurfactant-producing endophytes from Q. lancifolia tissues were carried out. The aim of the study was to contribute to the characterization of endophyte microbial and biochemical diversity in Q. lancifolia . A total of 42 endophytes (22 fungi and 20 bacteria) were isolated from Q. lancifolia plantlets, callus, cell suspensions and seeds, followed by microbial culture, and screening for extracellular foam production. Four fungi isolates were selected as foam-producing strains and were taxonomically identified using ITS-1 DNA sequencing. Foam production tests were performed using extracts from the liquid filtrate of cultures for subsequent triterpene screening by thin layer chromatography. Select extracts were purified and concentrated by solid phase extraction. Antibacterial activity was screened through agar diffusion and microdilution tests. Diplodia sp., Acremonium sp., Fusarium sp. and Aureobasidium sp. were identified as natural foam-producing endophytes. Liquid chromatography-mass spectrometry analyses revealed major differences between plant and fungi purified fractions. This work constitutes the first report of endophytic microorganisms associated with Q. lancifolia . It not only provides insights on the metabolic potential of these beings but also buttresses future investigations on their biotechnological applications.