Characterisation and antimicrobial activity of biosurfactant extracts produced by Bacillus amyloliquefaciens and Pseudomonas aeruginosa isolated from a wastewater treatment plant

Abstract

Biosurfactants are unique secondary metabolites, synthesised non-ribosomally by certain bacteria, fungi and yeast, with their most promising applications as antimicrobial agents and surfactants in the medical and food industries. Naturally produced glycolipids and lipopeptides are found as a mixture of congeners, which increases their antimicrobial potency. Sensitive analysis techniques, such as liquid chromatography coupled to mass spectrometry, enable the fingerprinting of different biosurfactant congeners within a naturally produced crude extract. Bacillus amyloliquefaciens ST34 and Pseudomonas aeruginosa ST5, isolated from wastewater, were screened for biosurfactant production. Biosurfactant compounds were solvent extracted and characterised using ultra-performance liquid chromatography (UPLC) coupled to electrospray ionisation mass spectrometry (ESI–MS). Results indicated that B. amyloliquefaciens ST34 produced C13–16 surfactin analogues and their identity were confirmed by high resolution ESI–MS and UPLC–MS. In the crude extract obtained from P. aeruginosa ST5, high resolution ESI–MS linked to UPLC–MS confirmed the presence of di- and monorhamnolipid congeners, specifically Rha–Rha–C10–C10 and Rha–C10–C10, Rha–Rha–C8–C10/Rha–Rha–C10–C8 and Rha–C8–C10/Rha–C10–C8, as well as Rha–Rha–C12–C10/Rha–Rha–C10–C12 and Rha–C12–C10/Rha–C10–C12. The crude surfactin and rhamnolipid extracts also retained pronounced antimicrobial activity against a broad spectrum of opportunistic and pathogenic microorganisms, including antibiotic resistant Staphylococcus aureus and Escherichia coli strains and the pathogenic yeast Candida albicans. In addition, the rapid solvent extraction combined with UPLC–MS of the crude samples is a simple and powerful technique to provide fast, sensitive and highly specific data on the characterisation of biosurfactant compounds.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-017-0363-8) contains supplementary material, which is available to authorized users.

Inhibitory effect ofBacillus subtilisWL-2 and its IturinA lipopeptides againstPhytophthora infestans

“…To obtain cell suspension (CS), LB liquid medium was inoculated with each strain and incubated for 20 h at 37°C and 200 rpm, and the final concentration (1×10 7 CFU/mL) was regulated by distilled water. Prepared 2% seed culture (SC, 1×10 7 CFU/mL) were transformed into flasks containing 100 mL of LB liquid medium and incubated at 30°C and 200 rpm for 96 h. Finally, the liquid culture was centrifuged (10,000 × g, 4°C) for 10 min, and LC were filtered using cellulose acetate membranes (0.22 µm) to obtain a cell-free supernatant (CFS) solution (26, 27). Eight-day-old P. infestans mycelium was scraped into 10 mL of distilled water and oscillated to expose sporangium; then, the sporangium suspension was regulated to 1×10 7 CFU/mL using distilled water.…”

Antimicrobial potential of haloalkaliphilic Nocardiopsis sp. AJ1 isolated from solar salterns in India

“…Surfactin is considered to be antibiotics due to their broad antimicrobial spectrum . The crude surfactin possesses antimicrobial activity against antibiotic resistant Staphylococcus aureus, E. coli strains and the pathogenic yeast Candida albicans . Surfactin and its derivatives also act as antiviral agents, antibiotics, antitumor agents, immunomodulators, or specific toxin‐inhibitors .…”

Biosurfactants: Eco-Friendly and Innovative Biocides against Biocorrosion

“…Glycolipid-based biosurfactants such as rhamnolipids primarily produced by Pseudomonas species also display algicidal, anti-amoebal, and zoosporicidal properties. These lipid compounds have also been reported to effectively kill various bacteria, as well as fungi and certain viruses [46][47][48][49]. The antibacterial properties and ability to disrupt biofilms by biosurfactants (rhamnolipids and sophorolipids) and sodium dodecyl sulphate (SDS), in combination with selected organic acids, were investigated by Rienzo et al [44].…”