2 - The biochemistry of ligninolytic fungi

Summary

Introduction

The principal relevance of ligninolytic fungi to the field of bioremediation lies in their ability to degrade aromatic compounds. There are three groups of aromatics that constitute substantial pollutants: polyaromatic hydrocarbons (PAHs), benzene/toluene/ethyl benzene/xylene (BTEX) and the synthetic substituted aromatics typified by the chlorophenols. It may well be that ligninolytic fungi can play a useful role in bioremediation of all three types of pollutant, but the most interest is in degradation of the first and last groups, as BTEX remediation can exploit bacterial populations that promise to be efficient contributors to the process. We will largely be concerned with systems that are of possible direct application to PAH degradation as the halogenated hydrocarbons are degraded by increasingly well-understood biochemical pathways (see Reddy, Gelpke & Gold, 1998; Reddy & Gold, 1999). One of the main difficulties in the development of practical bioremediation processes rests in bringing metabolically active organisms into contact with the pollutant (see Field et al., 1995; Boyle, Wiesner & Richardson, 1998; Head, 1998; Novotny et al., 1999). The secreted enzyme systems of ligninolytic fungi may prove to be a powerful tool for PAH removal, and it is this aspect of their biochemistry to which this chapter is directed.

PAHs are a class of carcinogenic chemical that are formed whenever organic materials are burned; the amount of PAHs in soils coming from atmospheric fall-out have been rising steadily over the twentieth century.