Abstract
BackgroundBiosurfactants, being highly biodegradable, ecofriendly and multifunctional compounds have wide applications in various industrial sectors including environmental bioremediation. Surfactin, a member of lipopeptide family, which is considered as one of the most powerful biosurfactants due to its excellent emulsifying activities as well as environmental and therapeutic applications. Therefore, the aim of this study was to investigate the newly isolated bacterial strain S2MT for production of surfactin-like biosurfactants and their potential applications for oil-contaminated soil remediation.ResultsIn this study, the strain S2MT was isolated from lake sediment and was identified as Bacillus nealsonii based on transmitted electron microscopy (TEM) and 16S rRNA ribo-typing. The strain S2MT produced biosurfactant that reduced the surface tension (34.15 ± 0.6 mN/m) and displayed excellent emulsifying potential for kerosene (55 ± 0.3%). Additionally, the maximum biosurfactant product yield of 1300 mg/L was achieved when the composition of the culture medium was optimized through response surface methodology (RSM). Results showed that 2% glycerol and 0.1% NH4NO3 were the best carbon/nitrogen substrates for biosurfactant production. The parameters such as temperature (30 °C), pH (8), agitation (100 rpm), NH4NO3 (0.1%) and NaCl (0.5%) displayed most significant contribution towards surface tension reduction that resulted in enhanced biosurfactant yield. Moreover, the extracted biosurfactants were found to be highly stable at environmental factors such as salinity, pH and temperature variations. The biosurfactants were characterized as cyclic lipopeptides relating to surfactin-like isoforms (C13–C15) using thin-layer chromatography (TLC), Ultra high performance liquid chromatography and mass spectrometry (UHPLC-MS). The crude biosurfactant product displayed up to 43.6 ± 0.08% and 46.7 ± 0.01% remediation of heavy engine-oil contaminated soil at 10 and 40 mg/L concentrations, respectively.ConclusionPresent study expands the paradigm of surfactin-like biosurfactants produced by novel isolate Bacillus nealsonii S2MT for achieving efficient and environmentally acceptable soil remediation as compared to synthetic surfactants.
Highlights
Biosurfactants, being highly biodegradable, ecofriendly and multifunctional compounds have wide applications in various industrial sectors including environmental bioremediation
Isolation, screening and identification of biosurfactant producing isolate S2MT Initially, total of 32 (n = 32) distinct bacterial colonies were isolated from the different layers of lake i.e. surface water, deep water and sediments, and all were screened for their biosurfactants production (Additional file 1: Table S2)
After experimental screening and preliminary identification the isolate S2MT was further selected for molecular identification, which was identified as Bacillus nealsonii, showing 99.93% similarity using 16S rRNA ribotyping, as illustrated in the phylogenetic tree (Additional file 1: Fig. S2)
Summary
Biosurfactants, being highly biodegradable, ecofriendly and multifunctional compounds have wide applications in various industrial sectors including environmental bioremediation. A member of lipopeptide family, which is considered as one of the most powerful biosurfactants due to its excellent emulsifying activities as well as environmental and therapeutic applications. The development of sustainable technology has driven the search for natural and biodegradable compounds to remediate sites contaminated with hydrocarbons. Phulpoto et al Microb Cell Fact (2020) 19:145. This has led to the discovery of surfactants from natural sources. The compounds have surface-active properties and one produced by microbes is termed as biosurfactant [1]. These biomolecules are produced by various microorganisms like bacteria, fungi, and yeast [2, 3]. Hydrophobic ‘tail’ is a hydrocarbon chain containing saturated/unsaturated and hydroxylated fatty alcohols or fatty acids and the hydrophilic ‘head’ is a polar group that contains mono, oligo or polysaccharides and peptides [5]
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