Iron-Stimulated Production and Antimicrobial Potential of a Novel Biosurfactant Produced by a Drilling Waste-Degrading Pseudomonas citronellolis Strain

A Pseudomonas citronellolis strain was isolated from drilling waste (DW). This strain utilizes DW as the sole energy and carbon source to produce biosurfactants (BSs). The BS produced was thermally stable, amorphous and includes a peptide structure. FeSO4, FeCl3 and Fe(NO3)(3) were supplemented at various concentration levels to assess possible enhancement of BS production and DW biodegradation. The limit concentration of Fe compounds between the increase in BS formation and microbial toxicity was 0.1 mM. FeCl3 enhanced DW biodegradation and more than doubled the BS formation yield, determining an optimization strategy for BS production. The BS was then partially purified and used against several Gram-negative and positive multi-drug resistant bacteria (such as Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli spp, Acinetobacter baumaniii, Enterococcus faecalis spp, Streptococcus pneumoniae, Staphylococcus aureus, Salmonella enterica). The minimum inhibitory concentration was defined at a range of 0.25 to 10 mg/mL. The antimicrobial properties of the partially purified BS established its effectiveness and suggested a down-stream processing cost reduction, as no additional purification steps were necessary. The study could lead to a sustainable low-cost bioprocess towards a circular bioeconomy because waste, a non-expensive substrate, is used; while the BS holds great potential as a novel compound with antibiotic and disinfectant-like action, following toxicity testing with human cells.

Automated summary

A strain of Pseudomonas citronellolis was isolated from drilling waste and used to produce biosurfactants. The addition of FeCl3 was found to enhance BS production and waste degradation. The partially purified BS showed antimicrobial properties against multi-drug resistant bacteria, suggesting a cost-effective and sustainable bioprocess with potential applications in antibiotic and disinfectant fields.