Environmental pollution is commonly related with chemical, petrochemical or pharmaceutical industries because they are responsible for the production of the majority of anthropogenic compounds, producing large volumes of some chemicals each year. Many of these anthropogenic compounds are either resistant to microbial degradation or toxic to potential microbial-degraders, when present in high concentrations and certain mixtures.

However, another group of industries is also responsible for the release in the environment of compounds with similar characteristics, although with a natural origin.

In fact, environmental pollution due to the release of natural phenolic compounds, from agro-industrial operations, has become widespread in the world. These compounds are present in many agro-industrial effluents and residues, like those produced in wine-distillery, olive oil extraction, green olive debittering, cork preparation, wood debarking and coffee production, creating great difficulties to their treatment.

Other aspects contribute to this environmental problem; many of these industries are seasonable and typical of regions, like the Mediterranean region, characterized by low technical and financial resources, water scarcity and progressive human and environmental desertification. The social and economical importance to maintain these industries and to assure their sustainability is obvious. In order to treat these effluents, the reduction of the organic load and of the toxicity to acceptable levels must be achieved, having in mind their final disposal.

Biodegradation is a natural process used world-wide in wastewater treatment plants and in solid waste composting operations and can also be an effective, low cost, sustainable process for the removal of toxic organic compounds, if "specialized microorganisms", capable of adaptation to the effluent conditions, are selected.

Among microorganisms, filamentous fungi can be an important source of phenol-degrading species as they grow frequently in wood where phenolic structures are present. However, organic compounds like phenol and its derivatives have toxic effects that limit the biological treatment, because they can be growth-rate inhibitory even to species that have the metabolic capability of using it as a substrate for growth.

In this context, the purpose of this study was to investigate the ability of the fungus Fusarium flocciferum to degrade some phenolic compounds namely, gallic, protocatechuic, vanillic, syringic, caffeic and ferulic acids and syringic aldehyde, usually present in agro-industrial wastes. The biodegradation assays were performed in liquid medium with the phenolic compounds as single substrates and as a synthetic mixture containing the 7 aromatic compounds. The results with single substrates indicated that in 24 hrs of incubation the fungus was able to reduce the phenolic concentration from 200 mg/l to below detection limits, except for syringic acid, being the lowest degradation rates found for this acid and its aldehyde. The biodegradation experiments with the mixture of phenolic compounds showed that after 8 hrs the total phenolic concentration was reduce from 350 mg/l to below the detection limits of all the tested compounds. In all the experiments a rise in the pH and an effective detoxification of the phenolic solutions were also observed (Table 1).

F. flocciferum was able to degrade the seven tested compounds either as single or mixed substrate, detoxifying the solutions. According to the authors, these results confer to this fungus a remarkable potential for its application in bioremediation and wastewater treatment, especially in detoxification of phenolic wastes.

Table 1. Values obtained in the biodegradation experiments with the mixture of seven phenolic compounds for COD (mg/l O₂), total phenols (mg/l), pH and ecotoxicity (EC₅₀-5 min (%). (The values are the arithmetic mean of at least two independent analyses).