I. Singleton, MICROBIAL-METABOLISM OF XENOBIOTICS - FUNDAMENTAL AND APPLIED-RESEARCH, Journal of chemical technology and biotechnology, 59(1), 1994, pp. 9-23
The ability of microorganisms to metabolise xenobiotic compounds has r
eceived much attention due to the environmental persistence and toxici
ty of these chemicals. The microbial degradation of xenobiotics is see
n as a cost effective method of removing these pollutants from the env
ironment by a process now known as bioremediation. Microbial treatment
of industrial effluents is also possible. Fundamental work has reveal
ed that a wide variety of microorganisms are capable of degrading an e
qually wide range of organic pollutants. Pure and mixed cultures of mi
croorganisms have been studied and degradation is observed under both
aerobic and anaerobic conditions. Breakdown products have been found d
uring work on the degradative pathways involved and toxicological asse
ssments using bacteria and higher organisms (fish, plants) have been u
sed to determine the toxicity of these intermediates. Many of the degr
adative genes responsible for xenobiotic metabolism are present on pla
smids, transposons or are grouped in clusters on chromosomes. This pro
vides clues to the evolution of degradative pathways and makes the tas
k of genetic manipulation easier such that new microbial strains capab
le of efficiently degrading pollutants can be developed. Several enzym
es involved in xenobiotic metabolism have been isolated and factors af
fecting their activity investigated. Genetically manipulated strains o
r naturally isolated organisms may be used in the treatment of industr
ial wastes or as inocula to enhance degradation in the environment. En
vironmental factors, including pH, temperature, bioavailability, nutri
ent supply and oxygen availability have been shown to affect xenobioti
c biodegradation. These factors must be optimised to obtain a satisfac
tory microbial treatment process. Using information gained from fundam
ental research, bioremediation technology has been used to detoxify di
fferent contaminated environments and the results of field studies are
very encouraging.