The most prevalent environmental hazard is petroleum pollution, which shows harmful effects on all marine ecosystems due to rapid industrialization leading to an increase in aromatic hydrocarbons over the years. The Environmental Protection Agency, USA, reported the contamination sources are massive: leakages from underground storage tanks, accidents in fuel transportation by ships; which are subject to corrosion, oil extraction, and processing; and inadequate release of oily waste generated by industries that use oil byproducts in the production of plastics, solvents, pharmaceuticals, and cosmetics, which cannot be reused or recycled, as they are toxic, flammable, pathogenic or corrosive. Moreover, for humans, hydrocarbons are considered highly toxic, carcinogenic, and mutagenic . The advancement of sustainable technologies tends towards the natural methods for the remediation of soil and water contaminants has increased based on different biological activities. Microorganisms most prominently have a great diversity of bacteria such as Actinobacteria, Mycobacterium, Penicillium, Mycococcus, Pseudomonas, Nitrosomonas, Flavobacterium, etc. that promote the cracking of hydrocarbons molecules (dioxins, benzene, polychlorinated biphenyls, toluene, etc.) by micelle formation, increasing their mobility, bioavailability and exposure to bacteria, thus favoring bioremediation[2–3]. Some microorganisms have started producing several classes of surface-active compounds such as glycolipids, lipopeptides, phospholipids, neutral lipids or fatty acids, and polymeric biosurfactants [4–6]. The surfactant-enhanced bioremediation emerges as a promising technology for the remediation of PAH or hydrophobic organic compounds contaminated from water and soil surface. In contrast to chemical surfactants, biosurfactant’s utilization for the bioremediation of contaminated water surface and oil spills is not yet well established. Interestingly, the attention of the scientific and industrial community recently focuses on determining potential biosurfactants that can be produced at a large scale because of their lower toxicity, optimal activity at extreme conditions of temperatures, pH levels, and salinity, a higher degree of biodegradability, and higher foaming capacity [7–8].
Biosurfactants contain both the hydrophilic and hydrophobic domains capable of interfacial tension and decreasing surface. Biosurfactant has various compounds like lipopeptides, neutral lipids, fatty acids, and glycolipids. These are non-toxic, biodegradable biomolecules that show the emulsification of hydrophobic compounds . Based on the biosurfactant domain, the hydrophilic domain comprises a carbohydrate, an amino acid, a phosphate group, or similar compounds. In contrast, the hydrophobic domain is most commonly comprised of the carboxylic acid chain. The present property of biosurfactant sustains to cut down the interfacial tensions and surface tensions and make them a potential candidate for enhancing oil degradation [10–11]. The biosurfactant production can be affected by various factors such as the nature of carbon and nitrogen sources used; phosphorus, iron, manganese, and magnesium may also be present. Besides, pH, temperature, agitation and mode of operation are the other essential factor that directly affects the quantity and quality of produced biosurfactant . Therefore, the development of more multifunctional biosurfactants is required to broaden the spectrum of properties available. The biosurfactant production on an industrial scale makes it more worthy for better and efficient bioprocesses to make them competitive because of the chemically synthesized compound's market due to inefficient bio-processing methodology and poor strain productivity . If the biosurfactants are produced from cheap substrates like agro-industrial wastes, which reduces the production cost. Therefore, it is beneficial to identify, isolate and characterize new strains producing biosurfactants from various natural sources like water bodies or contaminated soil. The research anticipated analyzing the stability and efficiency of a new lipopeptide biosurfactant produced by Paenibacillus sp. and the feasibility of its use in bioremediation.
In a previous study, we reported the biosurfactant production by Bacillus subtilis novel strain ANSKLAB03 that can yield 0.324 g of BS in 100mL of the medium . The phenotypic divergence and phylogenetic discreteness suggested that the mentioned Bacillus subtilis strain ANSKLAB03 was novel and submitted to the GenBank database. The identified Bacillus subtilis strain ANSKLAB03 was thermodynamically stable and had − 236.20kcal/mol of the free energy (ΔG) of the anticipated RNA structure . In a study, Bacillus tequilensis ZSB10 isolated from Mexican brines, the author was apt to produce extra-cellular as well as cell-bound biosurfactant employing nine broth cultures composed from hydrolyzates procure from the cellulosic and hemicellulosic fragments of wine-trimming wastes . Similarly, Paenibacillus macerans strain TKU029 can yield exopolysaccharides and the biosurfactant in a medium with 2% (w/v) of squid pen powder as the ace source of carbon/nitrogen. At a concentration of 2.76 g/L, biosurfactant can reduce water surface tension from 72.30 to 35.34 mN/m and can reach an emulsification index of up to 56% in the presence of machine oil with 24h incubation. This biosurfactant was found stable at 121°C for 20 min and a varying pH range of 3 to 11. There were no observable structural changes even in < 5% salt solutions .
The present study aims to examine the effect of the lipopeptide biosurfactant produced by novel gram-positive Paenibacillus sp. strain, isolated from brackish water lagoon, on oil spill degradation by a microbial consortium. The biosurfactant produced by isolated Paenibacillus sp. strain was screened, purified, quantified, and characterized by physicochemical properties. Its potential application for enhancing bioremediation was evaluated. The optimum dosage for the maximal output was evaluated. The study describes the location, isolation, screening, and characterization of biosurfactant-producing strain. Besides, extracellularly produced metabolites were extracted for further analysis. Series of assay confirmatory assays were performed for analysis metabolic action to determine the potential of Paenibacillus species in degrading the oil.
Subsequently, it is essential to determine the stability in the harsh environment as the biosurfactant activities are affected by physicochemical factors such as temperature, pH and salinity. Therefore the interactive to identify the effect of pH, temperature, and salinity on biosurfactant stability was tested using a design experiment-based response surface methodology (RSM) with the Box–Behnken experimental design using R programming .