Biodegradation of PCP by the Rhizobacteria Isolated from Pentachlorophenol-tolerant Crop Species
Pentachlorophenol (PCP) is a polychlorinated
aromatic compound that is widespread in industrial effluents and is
considered to be a serious pollutant. Among the variety of industrial
effluents encountered, effluents from tanning industry are very
important and have a serious pollution potential. PCP is also formed
unintentionally in effluents of paper and pulp industries. It is highly
persistent in soils and is lethal to a wide variety of beneficial
microorganisms and insects, human beings and animals. The natural
processes that breakdown toxic chemicals in the environment have
become the focus of much attention to develop safe and environmentfriendly
deactivation technologies. Microbes and plants are among
the most important biological agents that remove and degrade waste
materials to enable their recycling in the environment. The present
investigation was carried out with the aim of developing a microbial
system for bioremediation of PCP polluted soils. A number of plant
species were evaluated for their ability to tolerate different
concentrations of pentachlorophenol (PCP) in the soil. The
experiment was conducted for 30 days under pot culture conditions.
The toxic effect of PCP on plants was studied by monitoring seed
germination, plant growth and biomass. As the concentration of PCP
was increased to 50 ppm, the inhibition of seed germination, plant
growth and biomass was also increased. Although PCP had a
negative effect on all plant species tested, maize and groundnut
showed the maximum tolerance to PCP. Other tolerating crops
included wheat, safflower, sunflower, and soybean. From the
rhizosphere soil of the tolerant seedlings, as many as twenty seven
PCP tolerant bacteria were isolated. From soybean, 8; sunflower, 3;
safflower 8; maize 2; groundnut and wheat, 3 each isolates were
made. They were screened for their PCP degradation potentials.
HPLC analyses of PCP degradation revealed that the isolate MAZ-2
degraded PCP completely. The isolate MAZ-1 was the next best
isolate with 90 per cent PCP degradation. These strains hold promise
to be used in the bioremediation of PCP polluted soils.
 M.M. Haggblom, Microbial breakdown of halogenated aromatic
pesticides and related compounds. FEMS Microbiol. Rev., Vol.30, 1992,
pp. 357 -363.
 J. Valenzuela, U. Bumann, R. Cespedes, L. Padilla, B. Gonzalez,
Degradation of chlorophenols by Alcaligenes eutrophus JMP134 (pJP 4)
in bleached kraft mill effluent. Appl. Environ. Microbiol., Vol.63, 1997,
 Yan He, Jianming Xu, Caixian Tang, Yuping Wu., Facilitation of
Pentachlorophenol degradation in the rhizosphere of ryegrass (Lolium
perenne L.). Soil Biol. Biochem., Vol.37, 2005, pp, 2017 - 2024.
 A. M Ferro, R.C. Sims and B.Bugbee, Hycrest crested wheatgrass
accelerates the degradation of Pentachlorophenol in Soil. J. Environ.
Qual., Vol. 23, 1994b, pp, 272-279.
 Tessa Mills, Barbara Arnold, Sivakumaran, Grant Northcott, Iris
Vogeler, Brett Robinson, Cara Norling, Doris Leonil, Phytoremediation
and long term site management of soil contaminated with
pentachlorophenol (PCP) and heavy metals. J Environ. Manage., Vol.
79, 2006, pp, 232-241.
 R.I. Dams, G.I. Paton and K. Killham., Rhizoremediation of
pentachlorophenol by Sphingobium chlorophenolicum (ATCC 397233).
Chemosphere, Vol 68(5), 2007, pp. 864-870.
 J.G. Steiert and R.L. Crawford, Degradation of chlorinated phenols by a
pentachlorophenol degrading bacterium. Appl. Environ. Microbiol., Vol.
53, 1987, pp, 907-910.
 J. P. Chu and E.J.Kirsch, Metabolism of pentachlorophenol by axenic
bacterial culture. Appl. Environ. Microbiol., Vol. 23, 1972, pp. 1033-
 M.M. Haggblom, L.J. Nohynek and M.S. Salkinoja-Salonen,
Degradation and O- methylation of chlorinated phenolic compounds by
Rhodococcus and Mycobacterium strains. Appl. Environ. Microbiol.,
Vol.54,1988c, pp. 3043-3052.
 L. Saber Diane and R. L. Crawford, Isolation and characterization of
Flavobacterium strains that degrade pentachlorophenol. Appl. Environ.
Microbiol., Vol. 50, 1985, pp.1512 - 1518.
 I.S.Thakur, R. Sharma, S. Shukla, and A.H.Ahmed, Enumeration and
enrichment o pentachlorophenol degrading bacterial population of pulp
and paper mill in the chemostat. AMI Conference, Jaipur, November 25-
27, 2000, pp. 159.
 M.D. Webb, G. Ewbank, J. Perkins, A.J. McCarthy, Metabolism of
pentachlorophenol by Saccharomonospora viridis strains isolated from
mushroom compost. Soil Biol. Biochem., Vol. 33, 2001, pp.315-321.