227
oil may not be removed entirely with physicochemical processes. Therefore, further
consideration is given to natural substitutes. Microbial surfactants predominantly
increase the diffusion of pollutants in aqueous phase and enhance bioavailability of
insoluble substrates to microbes, thereby facilitating the subsequent elimination of
contaminants in biodegradation. Lai et al. (2009) demonstrated that microbial surfactants assisted in enhanced total petroleum hydrocarbon removal employing 0.2
mass% of rhamnolipids (23%) and surfactin (14%) than chemical surfactants Tween
80 (6%) and Triton X-100 (4%). An efficient microbial consortium was composed
by Deppe et al. (2005) using arctic bacteria like Agreia, Marinobacter,
Pseudoalteromonas, Pseudomonas, Psychrobacter, and Shewanella for dissociation
of crude oil and its components. Most commonly reported oil- degrading bacterial
genera include Acinetobacter, Marinococcus, Methylobacterium, Micrococcus,
Planococcus, Nocardia, and Rhodococcus (Sakalle and Rajkumar 2009).
In a study by Batista et al. (2010), Candida tropicalis secreted a biosurfactant
which removed motor oil from sand with removal efficiency of 78%–97%. Likewise,
Luna et al. (2013) reported a Lunasan, secreted by Candida sphaerica UCP 0995
which separated 95% of motor oil from sand. Several studies reported the prospective uses of bioremediation techniques in mangrove soils polluted with petroleum
hydrocarbons in Australian continent (Burns et al. 2000) and Brazil (Brito et al.
2009). More recently, Silva et al. (2014) evaluated the potential of Pseudomonas
cepacia CCT6659 biosurfactant for removing oil from contaminated beaker walls
and noticed an elimination rate of 80% suggesting the use of this microbial surfactant in cleaning of oil storage tanks. Marinobacter sp. producing a novel biosurfactant which function as biodispersant to combat marine oil spills was isolated by
Raddadi et al. (2017).
8.7 Role of Biosurfactants in Bioremediation of Recalcitrants
Over the years, pesticides were used for the control of pests and disease vectors in
agriculture. Nevertheless, improper utilization of these compounds resulted in environmental pollution due to their toxicity, bioaccumulation, instability, and persistence. Notably, the ecofriendly biological methods including natural attenuation,
immobilization of cells, biosurfactant production, and bioaugmentation were proved
to be affective in combating adverse effects of these compounds (Benimeli et al.
2018). Bioremediation strategies include in situ production of surface active compounds by microbes to enhance the bioavailability of chemical pollutants
(Gnanamani et al. 2010; Wattanaphon et al. 2008).
Microbial biosurfactants produce complexes with pollutants bound to the soil
particles and increase their availability through desorption. Strikingly, these hydrophobic pesticides become stable within the biosurfactant micelles which sequentially favor their solubility following exclusion in the washing process. Several
studies highlighted the crucial role of actinobacteria as the potential candidates to
remove organic and inorganic pollutants. A glucolipid-type biosurfactant produced
8 Marine Microbial Biosurfactants: Ecological and Environmental Applications
oil may not be removed entirely with physicochemical processes. Therefore, further
consideration is given to natural substitutes. Microbial surfactants predominantly
increase the diffusion of pollutants in aqueous phase and enhance bioavailability of
insoluble substrates to microbes, thereby facilitating the subsequent elimination of
contaminants in biodegradation. Lai et al. (2009) demonstrated that microbial surfactants assisted in enhanced total petroleum hydrocarbon removal employing 0.2
mass% of rhamnolipids (23%) and surfactin (14%) than chemical surfactants Tween
80 (6%) and Triton X-100 (4%). An efficient microbial consortium was composed
by Deppe et al. (2005) using arctic bacteria like Agreia, Marinobacter,
Pseudoalteromonas, Pseudomonas, Psychrobacter, and Shewanella for dissociation
of crude oil and its components. Most commonly reported oil- degrading bacterial
genera include Acinetobacter, Marinococcus, Methylobacterium, Micrococcus,
Planococcus, Nocardia, and Rhodococcus (Sakalle and Rajkumar 2009).
In a study by Batista et al. (2010), Candida tropicalis secreted a biosurfactant
which removed motor oil from sand with removal efficiency of 78%–97%. Likewise,
Luna et al. (2013) reported a Lunasan, secreted by Candida sphaerica UCP 0995
which separated 95% of motor oil from sand. Several studies reported the prospective uses of bioremediation techniques in mangrove soils polluted with petroleum
hydrocarbons in Australian continent (Burns et al. 2000) and Brazil (Brito et al.
2009). More recently, Silva et al. (2014) evaluated the potential of Pseudomonas
cepacia CCT6659 biosurfactant for removing oil from contaminated beaker walls
and noticed an elimination rate of 80% suggesting the use of this microbial surfactant in cleaning of oil storage tanks. Marinobacter sp. producing a novel biosurfactant which function as biodispersant to combat marine oil spills was isolated by
Raddadi et al. (2017).
8.7 Role of Biosurfactants in Bioremediation of Recalcitrants
Over the years, pesticides were used for the control of pests and disease vectors in
agriculture. Nevertheless, improper utilization of these compounds resulted in environmental pollution due to their toxicity, bioaccumulation, instability, and persistence. Notably, the ecofriendly biological methods including natural attenuation,
immobilization of cells, biosurfactant production, and bioaugmentation were proved
to be affective in combating adverse effects of these compounds (Benimeli et al.
2018). Bioremediation strategies include in situ production of surface active compounds by microbes to enhance the bioavailability of chemical pollutants
(Gnanamani et al. 2010; Wattanaphon et al. 2008).
Microbial biosurfactants produce complexes with pollutants bound to the soil
particles and increase their availability through desorption. Strikingly, these hydrophobic pesticides become stable within the biosurfactant micelles which sequentially favor their solubility following exclusion in the washing process. Several
studies highlighted the crucial role of actinobacteria as the potential candidates to
remove organic and inorganic pollutants. A glucolipid-type biosurfactant produced
8 Marine Microbial Biosurfactants: Ecological and Environmental Applications