Their study showed the significance of local microorganisms in the biodegradation
of specific pollutant in addition of necessary genetic material through gene augmentation. Their study also affirmed the capability of bioaugmentation to change the
local soil microbial gene pool.
Dejonghe et al. (2000) evaluated the effect of propagation of two numerous 2,4-D
degradation plasmids available in the B (lower) and A (upper) horizon of a soil. The
application of an auxotrophic Pseudomonas putida strain that poses either of the two
plasmids lead to enhance population of transconjugants (>10
5 g
À1 ) in B and A
horizons. It was further revealed that the donor population reduces following the
bioaugmentation to the soil while the growth of transconjugant populations could be
linked to the degradative potential of 2,4-D. It was later observed that the process of
bioaugmentation led to improved 2,4-D degradation in the B horizon which does not
possess any local degrader population when compared to the A horizon which had a
larger number of indigenous degrader population. Their study also established that
gene bioaugmentation could be applied for bioremediation of heavily polluted soil.
The application of mobile genes in bioaugmentation was also established in a review
documented by Top et al. (1999).
15.3 Microbial Derived Materials that Could Enhance
the Process of Bioaugmentation
The process of bioaugmentation could be enhanced through the addition of enzyme
or biosurfactant when combined or added singly in addition to microbial inoculant.
The application of biosurfactant has been established for the bioremediation of
organic polluted material or heavy metal contaminated environment (Garcia-Junco
et al. 2003; Hong et al. 2002, Maier et al. 2001, Mata-Sandoval et al. 2002, Sandrin
et al. 2000, Sekelsky and Shreve 1999). They possess the capability to prevent the
adverse effect of metal toxicity on microbial inoculants and enhance the level of
organic substrates available for degradation (Sandrin et al. 2000; Rahman et al.
2003). Sandrin et al. (2000) established that the application of metal-complexing
with the biosurfactant mainly from rhamnolipid for reducing metal toxicity in a
model polluted system. The experiment was performed in the presence of
naphthalene-degrading Burkholderia sp. together with naphthalene and Cd. It was
revealed that the addition of rhamnolipid prevented the eliminated Cd toxicity after
the addition of ten-fold concentration of the Cd. It was discovered that at a lower
concentration the rhamnolipid decreases and exhibited no impact on Cd toxicity. The
authors affirmed that the presence of rhamnolipid reduces Cd toxicity by enhanced
naphthalene bioavailability, LPS release, and metal complexation. Some other
scientists have validated the application of enzyme that was encapsulated in dead
microbial cells or in their purified form for the reduction of contamination (Zhao
et al. 2003, Zhou 2003, Zhou and Thompson 2002, Zhou and Tiedje 1995,
Zouboulis et al. 2001, Wackett et al. 2002, Bhandari and Xu 2001).
390
C. O. Adetunji and O. A. Anani
of specific pollutant in addition of necessary genetic material through gene augmentation. Their study also affirmed the capability of bioaugmentation to change the
local soil microbial gene pool.
Dejonghe et al. (2000) evaluated the effect of propagation of two numerous 2,4-D
degradation plasmids available in the B (lower) and A (upper) horizon of a soil. The
application of an auxotrophic Pseudomonas putida strain that poses either of the two
plasmids lead to enhance population of transconjugants (>10
5 g
À1 ) in B and A
horizons. It was further revealed that the donor population reduces following the
bioaugmentation to the soil while the growth of transconjugant populations could be
linked to the degradative potential of 2,4-D. It was later observed that the process of
bioaugmentation led to improved 2,4-D degradation in the B horizon which does not
possess any local degrader population when compared to the A horizon which had a
larger number of indigenous degrader population. Their study also established that
gene bioaugmentation could be applied for bioremediation of heavily polluted soil.
The application of mobile genes in bioaugmentation was also established in a review
documented by Top et al. (1999).
15.3 Microbial Derived Materials that Could Enhance
the Process of Bioaugmentation
The process of bioaugmentation could be enhanced through the addition of enzyme
or biosurfactant when combined or added singly in addition to microbial inoculant.
The application of biosurfactant has been established for the bioremediation of
organic polluted material or heavy metal contaminated environment (Garcia-Junco
et al. 2003; Hong et al. 2002, Maier et al. 2001, Mata-Sandoval et al. 2002, Sandrin
et al. 2000, Sekelsky and Shreve 1999). They possess the capability to prevent the
adverse effect of metal toxicity on microbial inoculants and enhance the level of
organic substrates available for degradation (Sandrin et al. 2000; Rahman et al.
2003). Sandrin et al. (2000) established that the application of metal-complexing
with the biosurfactant mainly from rhamnolipid for reducing metal toxicity in a
model polluted system. The experiment was performed in the presence of
naphthalene-degrading Burkholderia sp. together with naphthalene and Cd. It was
revealed that the addition of rhamnolipid prevented the eliminated Cd toxicity after
the addition of ten-fold concentration of the Cd. It was discovered that at a lower
concentration the rhamnolipid decreases and exhibited no impact on Cd toxicity. The
authors affirmed that the presence of rhamnolipid reduces Cd toxicity by enhanced
naphthalene bioavailability, LPS release, and metal complexation. Some other
scientists have validated the application of enzyme that was encapsulated in dead
microbial cells or in their purified form for the reduction of contamination (Zhao
et al. 2003, Zhou 2003, Zhou and Thompson 2002, Zhou and Tiedje 1995,
Zouboulis et al. 2001, Wackett et al. 2002, Bhandari and Xu 2001).
390
C. O. Adetunji and O. A. Anani