225
8.4 Role of Biosurfactants in Bioremediation
of Metal-Contaminated Soils
Heavy metal pollution in urban areas and agricultural lands was caused by the activities like mining, production, and utilization of synthetic commodities (e.g., pesticides, paints, batteries, industrial waste materials). In contrast to the organic
molecules, restoration of metal polluted environments is predominantly demanding
as metals can be either biodegraded or biotransformed. Therefore, biological processes were considered as effective alternatives in the restoration of metal polluted
environments. Marine microorganisms are found to interact with and modify the
characteristics of a variety of noxious and nonhazardous metals (Haferburg and
Kothe 2007). In a study, Von Canstein et al. (2002) reported efficient removal of
mercury by a consortium of marine bacteria in a bioreactor. Interestingly, the ability
of chelation of toxic heavy metals by bacteria of marine origin was reported in
Enterobacter cloacae showing chelating efficiency up to cadmium (65%), copper
(20%), and cobalt (8%) at 100 mg/L of metal concentration (Iyer et al. 2005). In
another study, Abd-Elnaby et al. (2011) investigated a marine Vibrio harveyi capable of bioaccumulating Cd up to 23.3 mg Cd
2+
/g of dry cells. Similarly, purple
nonsulfur marine bacteria such as Rhodobium marinum and Rhodobacter sphaeroides were able to remove heavy metals like Cu, Zn, Cd, and Pb either by biosorption
or biotransformation (Panwichian et al. 2011).
Remarkably, enhanced removal efficiency of Cd (99%) and phenanthrene
(80–88%) was observed with the exploitation of lipopeptides suggesting their application in concurrent exclusion of heavy metal ions and organic contaminants (Lima
et al. 2011). Likewise, Wang and Mulligan (2009) described the prospective of
microbial surfactants to remove arsenic from mine tailings. In a study by Gnanamani
et al. (2010), a marine Bacillus sp. MTCC 5514 produced potent biosurfactant
which can remove Cr (VI) through bioremediation. Similarly, Asci et al. (2010)
established that metal ions (91.6% of Cd and 87.2% of Zn) may possibly extract
from quartz by treating with rhamnolipid. The processes promoting formation of
biosurfactant metal complexes include ion exchange, precipitation-dissolution,
counter-ion association, and electrostatic interaction (Rufino et al. 2011). In another
study, Rangarajan and Sen (2013) evaluated the elimination of calcium, magnesium. and Fe (II) in bubble column experiments utilizing lipopeptide secreted by
Bacillus megaterium strain of marine origin. It is notable that a surface-active compound produced by B. subtilis ICA56 was evidenced to be efficient in exclusion of
metals such as Cu, Cr, and Zn from contaminated systems (de França et al. 2015).
Yang et al. (2016) showed toxic metal removal efficiency (44.0% for Zn, 52.2% for
Mn, 37.7% for Cd) of biosurfactant produced by Burkholderia sp. Z-90. In a recent
study, Tang et al. (2018) depicted the enhanced removal of toxic metals from sludge
in the electrokinetic tests by using rhamnolipid, saponin, and sophorolipid,
respectively.
8 Marine Microbial Biosurfactants: Ecological and Environmental Applications
8.4 Role of Biosurfactants in Bioremediation
of Metal-Contaminated Soils
Heavy metal pollution in urban areas and agricultural lands was caused by the activities like mining, production, and utilization of synthetic commodities (e.g., pesticides, paints, batteries, industrial waste materials). In contrast to the organic
molecules, restoration of metal polluted environments is predominantly demanding
as metals can be either biodegraded or biotransformed. Therefore, biological processes were considered as effective alternatives in the restoration of metal polluted
environments. Marine microorganisms are found to interact with and modify the
characteristics of a variety of noxious and nonhazardous metals (Haferburg and
Kothe 2007). In a study, Von Canstein et al. (2002) reported efficient removal of
mercury by a consortium of marine bacteria in a bioreactor. Interestingly, the ability
of chelation of toxic heavy metals by bacteria of marine origin was reported in
Enterobacter cloacae showing chelating efficiency up to cadmium (65%), copper
(20%), and cobalt (8%) at 100 mg/L of metal concentration (Iyer et al. 2005). In
another study, Abd-Elnaby et al. (2011) investigated a marine Vibrio harveyi capable of bioaccumulating Cd up to 23.3 mg Cd
2+
/g of dry cells. Similarly, purple
nonsulfur marine bacteria such as Rhodobium marinum and Rhodobacter sphaeroides were able to remove heavy metals like Cu, Zn, Cd, and Pb either by biosorption
or biotransformation (Panwichian et al. 2011).
Remarkably, enhanced removal efficiency of Cd (99%) and phenanthrene
(80–88%) was observed with the exploitation of lipopeptides suggesting their application in concurrent exclusion of heavy metal ions and organic contaminants (Lima
et al. 2011). Likewise, Wang and Mulligan (2009) described the prospective of
microbial surfactants to remove arsenic from mine tailings. In a study by Gnanamani
et al. (2010), a marine Bacillus sp. MTCC 5514 produced potent biosurfactant
which can remove Cr (VI) through bioremediation. Similarly, Asci et al. (2010)
established that metal ions (91.6% of Cd and 87.2% of Zn) may possibly extract
from quartz by treating with rhamnolipid. The processes promoting formation of
biosurfactant metal complexes include ion exchange, precipitation-dissolution,
counter-ion association, and electrostatic interaction (Rufino et al. 2011). In another
study, Rangarajan and Sen (2013) evaluated the elimination of calcium, magnesium. and Fe (II) in bubble column experiments utilizing lipopeptide secreted by
Bacillus megaterium strain of marine origin. It is notable that a surface-active compound produced by B. subtilis ICA56 was evidenced to be efficient in exclusion of
metals such as Cu, Cr, and Zn from contaminated systems (de França et al. 2015).
Yang et al. (2016) showed toxic metal removal efficiency (44.0% for Zn, 52.2% for
Mn, 37.7% for Cd) of biosurfactant produced by Burkholderia sp. Z-90. In a recent
study, Tang et al. (2018) depicted the enhanced removal of toxic metals from sludge
in the electrokinetic tests by using rhamnolipid, saponin, and sophorolipid,
respectively.
8 Marine Microbial Biosurfactants: Ecological and Environmental Applications