Production and characterization of biosurfactant from novel strains isolated from environmental samples

Although the production of the crude oil sector holds immense importance in India’s industrial economy, it also contributes significantly to environmental degradation by contaminating the air, water, and land. As a significant portion of the naturally occurring aliphatic and aromatic hydrocarbons found in crude oil are recalcitrant complex to degrade, surfactants and emulsifiers are applied to oil-contaminated areas to minimize interfacial and surface tension and facilitate hydrocarbon uptake and emulsification. These agents create micelles at the interface between two immiscible fluids, such as water and oil. However, microbial surfactants are now in the spotlight due to high manufacturing costs, toxicity, and lack of biodegradability of chemical surfactants. Biosurfactants (BS) are produced by various microorganisms, but compared to their synthetic equivalents, their commercial success has been hindered by factors such as low yield, higher production costs, low recovery, and high purifying costs. In the present study, 21 isolates from contaminated air, water, and soil were subjected to tests for BS production. Four isolates were affirmed as efficient BS-producing strains and they were identified as Pseudomonas aeruginosa, Enterobacter mori, Bacillus siamensis, and Aspergillus niger by 16SrRNA and 18sRNA sequencing. Crude BS extracted from the isolates were identified as phospholipid, rhamnolipid, and lipopeptide based on qualitative analysis and thin layer chromatography. The maximum percentage of emulsification index (%E24) by the isolates was found for BS/diesel emulsion (73 ± 1.40). There was an efficient reduction in surface tension with a lower critical micelle concentration by the crude BS of all the isolates. Fourier transform infrared analysis of the crude BS of the isolates exhibited prominent bands corresponding to amine (NH group), carbonyl (C=O) stretching, and amine (NH) bending, thereby indicating the presence of proteins. Gas chromatography-mass spectrometry analysis of the crude BS produced by B. siamensis and A. niger revealed hexadecanoic acid as a major fatty acid in the samples. Our study has reported E. mori and B. siamensis as BS producers for the 1st time. This represents a significant addition to the known microbial sources for BS production in a commercial-level processing and large-scale production for consumer usage.