## 1 Introduction  
Heavy dependence on petroleum products as a major energy source has led to the contamination of soils by oil-derived hydrocarbons to a great extent [1]. Soil contamination by hydrocarbons can be a result of an improper production process (i.e., oil spills from drilling), transport (i.e., oil spills from tankers or pipelines), storage (i.e., leaking storage tanks), or an improper disposal process. Soil hydrocarbon contamination can affect the functional equilibrium that exists between soil biota and their natural environment. Although numerous physicochemical remediation techniques can be applied to clean up oil-polluted soils, these techniques are expensive and disruptive [2]. The application of biological remediation techniques, such as biostimulation and bioaugmentation, as well as plant-assisted bioremediation for hydrocarbon-contaminated soils, offers generally cheaper and more environmentally friendly solutions for clean-up of polluted sites [3; 4]. Though the use of different hydrocarbon-degrading bacteria, including _Pseudomonas_ spp., for the bioremediation of hydrocarbon-contaminated soils, has been successfully implemented, the main problem these bio-degraders encounter is the low solubility and high hydrophobicity of the oil-derived pollutants [5] due to the fact that hydrocarbons are strongly bonded to soil particles and are not available to the bacteria [6]. In this context, the use of biosurfactants for the enhancement of the bioremediation of soil hydrocarbon contamination has been recommended due to their non-toxic nature and biodegradability with no compromise in foaming properties [7]. Biosurfactant application can increase the bacterial cell surface hydrophobicity, allowing the hydrophobic substrates to interact with bacterial cells more effectively [5]  
Rhamolipid-type biosurfactants belong to a group of anionic surfactants comprising of l-(+)-rhammose and \(\beta\)-hydroxyalkanoic acid units [8]. _Pseudomonas aeruginosa_ is the most widely studied rhamnpid-producing bacterium known for its ability to metabolize a variety of hydrophobic substrates, including n-alkanes, hexadecane, and oils [9]. Di-rhammolipid synthesis in _P. aeruginosa_ occurs in three consecutive enzymatic reactions: 3-(3-hydroxyalkanoyloxy) alkanoic acid (HAA) synthesis catalyzed by rhamnyltransferase I (_Rhl_A), a glycosyltransferase reaction catalyzed by glycosyltransferase (_Rhl_B) to form mono-rhammolipids, and the reaction catalyzed by rhamnaserase II (_Rhl_C) that yields di-rhammolipids [10]. The first two enzymes encoded by _Rhl_A and _Rhl_B genes are both located in the _Rhl_AB operon but are independently involved in rhamnolipid biosynthesis [11]. Studies on the combined use of rhamnpids and rhamnpid-producing bacterial strains for the bioremediation of hydrocarbon-contaminated soils are scarce; at the same time, their role in the remediation of crude oil-contaminated sites has been documented by many researchers [12; 13; 14]. Though much work has been conducted on rhamnpid production focused on _P. aeruginosa_ and other _Pseudomonas_ strains, rhamnpid production has also been reported for bacteria belonging to other genera, such as _Acinetobacter_[15; 16]_Enterobacter_[16], _Pantoea_[16], and _Serratia_[17] Studies have shown that bioaugmentation is most efficient in cases when the augmented bacteria are inherent in the polluted soils [3; 18]. On 28 January 2017, near the entire region of the Tamil Nadu shoreline of India, the collision of two merchant vessels caused the spill of hazardous oil and liquid petroleum gas (LPG). This oil spill, accounting for a quantity of about 1.1 metric tonnes, has caused severe damage to the ecosystem, marine life, and presents health hazards to the residents living in the vicinity of the seashore.