aged for 1 month, 12 months, and 24 months using both single and multiple
washing. The washing efficiency was as high as 80%. Regardless of the applied
washing mode, the removal of Cd and Pb was not affected by the contamination age,
whereas the removal of Cu, Ni, and Zn was higher in soils that had been aged for a
shorter time (Kulikowska et al. 2015b). Bezza and Chirwa (2016) investigated the
biosurfactant-enhanced bioremediation of aged PAHs when an additional
biosurfactant from Pseudomonas aeruginosa and stimulation of the biosurfactant
in situ production were applied. The biosurfactant-enhanced degradation of PAHs
was 86.5% and 57% in the controls with no second biosurfactant. The additional
biosurfactant increased the PAHs bioavailability, thus stimulating the growth of
degraders. Then, the population growth led to the depletion of bioavailable PAHs,
which triggered an in situ biosurfactant production.
24.2.4.5 Biosurfactant in Prevention of Soil Contamination
As stated above, the assumed low biosurfactant toxicity is not necessarily displayed
under all conditions. However, the specific toxicity of some biosurfactants can be
appropriately used in many fields. Biosurfactants can actually be used as
biopesticides, thus replacing chemical pesticides in order to reduce the pollution of
soil, water, and sediment. Increasing amount of studies have already proved the
possibility of using biosurfactants against pathogens in agriculture. For example,
potato late blight disease caused by pathogen Phytophthora infestans was significantly reduced by biosurfactant-producing strain Pseudomonas koreensis and its
biosurfactant (Hultberg et al. 2010). On a similar token, rhamnolipids can be
effectively used against Fusarium verticillioides to control the stalk and ear rot
disease of maize (Borah et al. 2016).
24.3 Perspectives of Enzymes in Remediation Techniques
Enzymes are naturally present in soil ecosystems. They are produced by soil
microorganisms as well as by plants and soil invertebrates. Typical enzymes with
potential for bioremediation are listed in Table 24.1. Many enzymes, e.g., peroxidases, laccases, tyrosinases, organophosphorous hydrolases and dehalogenases,
lipases, proteases, phosphotriesterases, nitrile- and cyanide-degrading enzymes,
and mono- and dioxygenases have been studied for decades to treat the targeted
organic compounds, e.g., hydrocarbons; phenols; polyaromatic, nitroaromatic, and
chlorinated compounds; dyes; organophosphorous pesticides; nerve/paralyzing
agents; or inorganic compounds, e.g., those of metals or metalloids (PiotrowskaDługosz 2017). Fungi and bacteria are the most studied producers of these enzymes
(Piotrowska-Długosz 2017); however, marine microorganisms producing enzymes
with specific and promising properties are also widely tested (Sivaperumal et al.
2017).
24 Modern Bioremediation Approaches: Use of Biosurfactants, Emulsifiers. . .
505
washing. The washing efficiency was as high as 80%. Regardless of the applied
washing mode, the removal of Cd and Pb was not affected by the contamination age,
whereas the removal of Cu, Ni, and Zn was higher in soils that had been aged for a
shorter time (Kulikowska et al. 2015b). Bezza and Chirwa (2016) investigated the
biosurfactant-enhanced bioremediation of aged PAHs when an additional
biosurfactant from Pseudomonas aeruginosa and stimulation of the biosurfactant
in situ production were applied. The biosurfactant-enhanced degradation of PAHs
was 86.5% and 57% in the controls with no second biosurfactant. The additional
biosurfactant increased the PAHs bioavailability, thus stimulating the growth of
degraders. Then, the population growth led to the depletion of bioavailable PAHs,
which triggered an in situ biosurfactant production.
24.2.4.5 Biosurfactant in Prevention of Soil Contamination
As stated above, the assumed low biosurfactant toxicity is not necessarily displayed
under all conditions. However, the specific toxicity of some biosurfactants can be
appropriately used in many fields. Biosurfactants can actually be used as
biopesticides, thus replacing chemical pesticides in order to reduce the pollution of
soil, water, and sediment. Increasing amount of studies have already proved the
possibility of using biosurfactants against pathogens in agriculture. For example,
potato late blight disease caused by pathogen Phytophthora infestans was significantly reduced by biosurfactant-producing strain Pseudomonas koreensis and its
biosurfactant (Hultberg et al. 2010). On a similar token, rhamnolipids can be
effectively used against Fusarium verticillioides to control the stalk and ear rot
disease of maize (Borah et al. 2016).
24.3 Perspectives of Enzymes in Remediation Techniques
Enzymes are naturally present in soil ecosystems. They are produced by soil
microorganisms as well as by plants and soil invertebrates. Typical enzymes with
potential for bioremediation are listed in Table 24.1. Many enzymes, e.g., peroxidases, laccases, tyrosinases, organophosphorous hydrolases and dehalogenases,
lipases, proteases, phosphotriesterases, nitrile- and cyanide-degrading enzymes,
and mono- and dioxygenases have been studied for decades to treat the targeted
organic compounds, e.g., hydrocarbons; phenols; polyaromatic, nitroaromatic, and
chlorinated compounds; dyes; organophosphorous pesticides; nerve/paralyzing
agents; or inorganic compounds, e.g., those of metals or metalloids (PiotrowskaDługosz 2017). Fungi and bacteria are the most studied producers of these enzymes
(Piotrowska-Długosz 2017); however, marine microorganisms producing enzymes
with specific and promising properties are also widely tested (Sivaperumal et al.
2017).
24 Modern Bioremediation Approaches: Use of Biosurfactants, Emulsifiers. . .
505