Use of olive mill wastewater as a suitable substrate for the production of laccase by Cerrena consors

Olive mill wastewater (OMWW) is the toxic, malodorous, recalcitrant waste from the three-phase decanter system used in the processing of olives for oil. The waste has a high organic load, and is high in polyphenols which largely account for its phytotoxicity, preventing its use in irrigation or its discharge into waterways. A white-rot basidiomycete, previously found to reduce phenols and phytotoxicity of OMWW, produced substantial laccase activity during cultivation. Putatively identified as Cerrena consors, laccase production was maximal during idiophase. Copper (0.75 mM) increased laccase activity by more than 500% and addition of spent OMWW-based culture fluid to the medium was also inductive. The laccase isoform pattern changed depending on whether fresh or aged OMWW was used as the growth medium. Moreover, OMWW was found to be a source of natural laccase mediators which appear to have increased the effectiveness of phenol removal from the wastewater. Laccases can degrade and detoxify many organic pollutants, but their use is hindered by the inability to produce them cheaply. This work also suggests that OMWW may be a useful substrate for the production of laccases from white-rot fungi that are capable of utilising toxic wastes such as OMWW containing polyphenols.