Biotechnology Letters 22: 469–472, 2000.
© 2000 Kluwer Academic Publishers. Printed in the Netherlands.
Biodegradation of soil-adsorbed polycyclic aromatic hydrocarbons by the
white rot fungus Pleurotus ostreatus
Facundo J. M
, Vanessa Z. Hern
& Rafael V
Centro de Investigacion Cient´ıﬁca y de Educaci´on Superior de Ensenada, AP 2732, Ensenada, B. C. CP 22830,
Instituto de Biotecnolog´ıa, UNAM AP 510-3, Cuernavaca, Mor., CP 62270, M´exico
Present address: Dept. Acuicultura, CICESE, P.O. Box 434844, San Diego, CA 92143, USA
Author for correspondence (Fax: 52-6-1750534; E-mail: email@example.com)
Received 16 December 1999; Revisions requested 24 December 1999; Revisions received 25 January 2000; Accepted 26 January 2000
Key words: biodegradation,hydrogenperoxide, Pleurotus ostreatus, polycyclic aromatichydrocarbons, surfactants
The white rot fungus, Pleurotus ostreatus, metabolized four soil adsorbed polycyclic aromatic hydrocarbons:
50% of pyrene (0.1 mg g
dry soil), 68% of anthracene and 63% of phenanthrene were mineralized after 21
d. Biodegradation was increased to 75%, 80% and 75%, respectively of the initial concentration when 0.15%
Tween 40 was added. Biodegradation of pyrene in the presence of surfactant and H
(1.0 mM) was 90%.
Benz[a]pyrenewas also oxidized by Pleurotus ostreatus but it is not mineralized.
The current interest in the biodegradation of poly-
cyclic aromatic hydrocarbons (PAHs) is due to some
of these ubiquitous pollutants being suspected as hu-
man carcinogens. PAHs are components of coal tar,
creosote, and crude oil and are formed by the in-
complete combustion of organic material (Bezalel
et al. 1996a). Soils, sludges, and sediments contain-
ing such hazardous wastes as dioxin, polychlorinated
biphenyls, and polycyclic aromatics (PAHs) are of
major concern. Various methods, such as addition of
chemical oxidants, ﬂushing, and microbial degrada-
tion, have been employed to destroy recalcitrant or
hazardous wastes in soils (George & Neufeld 1989).
Some of the most difﬁcult bioremediation problems
involve the decontamination of soils contaminated
with oil and coal tar residues. These problems arise
because of the recalcitrant nature of polycyclic aro-
matic hydrocarbons and the difﬁculties in achieving
effective contact with these substances when they are
associated with the soil (Brodkorb & Legge 1992).
The issue of sorption and bioavailability is of interest
mainly because it is believed that poor availability is
one of the reasons for the limited success of biore-
mediation technology. Research designed to explain
and overcome problems of poor availability of chemi-
cals that are otherwise easily biodegradedwouldmake
bioremediation more widely used. Sorption, it is gen-
erally believed, tends to decrease the availability of the
adsorbed organic compounds (Gray et al. 1994, Laor
et al. 1996).
Fungi do not utilize phenanthrene as the sole
carbon source and energy but instead cometabo-
lize the PAH to hydroxylated products (Sutherland
et al. 1991). Many nonligninolytic fungi metabolize
phenanthrene in a highly regio- and stereoselective
manner, via cytochrome P-450 monooxygenase and
epoxidehydrolase, to producephenanthrenetrans-1,2-
,trans-3,4-, and trans-9,10-dihydrodiol; 1-, 2-, 3-, 4-,
and 9-phenanthrols; and sulfate, glucoside, and glu-
curonide conjugates of the primary metabolite. Rel-
atively few nonligninolytic fungi have the ability to
degrade PAHs to carbon dioxide. In contrast, ligni-
nolytic fungi have the ability to cleave the aromatic
rings and mineralize PAHs (Bezalel et al. 1996b).
Benzo[a]pyrene, B[a]P, a 5-ring polycyclic aro-
matic hydrocarbon, is a carcinogen which can be