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Exploration of crude oil often results in accidental spillage and environmental contamination due to its various toxic components [22, 23]. Crude oil exploration fields are also home to oil‐degrading microbes that are capable of using spilled oil as their carbon source and can remove crude oil from contaminated sites [24]. Numerous oil‐degrading bacteria strains have been isolated from both cold [9] and hot [25] environments. Microbe‐enhanced oil recovery tests performed using biosurfactant‐producing microorganisms are briefly described in Chapter 5.

In the last few years, attempts have been made to identify possible biosurfactant‐producing microorganisms [4]. Some of the key genera that make biosurfactants are Acinetobacter, Bacillus, Azotobacter, Candida [18], Enterobacter, Micrococcus, Oceanobacillus, Pseudomonas, Rhodococcus, Serratia and Stenotrophomonas [18, 26]. Rhodococcus sp. HL‐6 reported from petroleum‐contaminated soil produces glycolipid biosurfactants and has been successfully exploited for the remediation of crude oil contaminated sites [27]. Pseudomonas is one of the most widely described genera for the production of biosurfactants [28]. Bacillus subtilis and Pseudomonas aeruginosa have also been reported from oil‐contaminated soils and have been shown to be a potential candidate for the degradation of petroleum hydrocarbons [18, 28, 29]. Similarly, biosurfactants derived from the consortium of P. aeruginosa and Rhodococcus strains have been reported to degrade more than 90% of oil sludge [30]. P. aeruginosa RS29 isolated from crude oil‐contaminated sites has been reported to produce potent biosurfactants with enhanced foaming and emulsifying properties [28]. The thermophilic hydrocarbon‐degrading bacteria P. aeruginosa AP02‐1 are known to produce biosurfactants using hydrocarbon as the sole source of carbon [31]. Biosurfactant BSW10 derived from P. aeruginosa W10 has been successful in phenanthrene and fluoranthene biodegradation from oil‐contaminated sites [32].

The marine microbiome is a global collective of all microorganisms. This is a good source of useful microbes for use in bioproducts. Specific microbial communities living in marine and coral reefs have been reported to be beneficial to humans. Acinetobacter, Alteromonas, Azotobacter, Corynebacteria, and Myroids are some marine microorganisms that have been reported to produce biosurfactants [12], while Alcanivorax and Halomonas have also been reported to produce biosurfactants in marine environments and to degrade hydrocarbons [33]. Alcanivorax uses n‐alkanes from oil‐contaminated sites producing glycolipid biosurfactants [34]. Species of Halobacterium viz. Haloferax, Halovivax, and Haloarcula have been described as biosurfactant producers and are known to utilize different hydrocarbons [35]. Marinobacter, Methylophagia, Roseovarius, Thalassospria, Rheinheimera, and Sphingomonas are the other genera known to produce biosurfactants and have been able to degrade aliphatic and aromatic hydrocarbons [36].

Many potential genes that are responsible for biosurfactant production have now been identified and described. Leite et al. [37] describe the presence of rhlAB and alkB genes from bacterial genomes isolated from soil contaminated with crude oil. The main pollutants of crude oil are alkanes and aromatic hydrocarbons. These bacterial genomes contain RhlAB genes and are responsible for the production of rhamnolipid biosurfactants and the alkB gene (alkane mono‐oxygenase) mediates the degradation of petroleum hydrocarbons by the alkane mono‐oxygenase enzyme system. Similarly, another gene reported from oil‐contaminated soil is the naphthalene dioxygenase (Nah) gene, which contributes to the degradation of both alkanes and aromatic hydrocarbons [38]. Likewise, a lipopeptide biosurfactant surfactin is produced by three genes, srfA, srfB, and srfC, present in srfA operon [35, 39].

All the results reported in this section provide scientific evidence that oil‐contaminated soil and marine environment are good sources of potential microbes that produce biosurfactants and degrade hydrocarbons. Microbial genes from contaminated environments could be used to produce environmentally safe biosurfactants that help with bioremediation and at the same time reduce production costs involved in the process.