Abstract for presentation at Chemeca 2007

Natural organic matter (NOM) is a brown-coloured breakdown product of largely vegetation origin which occurs in natural water sources and which negatively impacts drinking water quality and water treatment processes. Most NOM removal processes lead to concentrated NOM-containing wastes which must be treated prior to disposal. White rot fungi possess a non-specific extracellular oxidative enzyme system composed of lignin peroxidase (LiP), manganese-dependent peroxidase (MnP) and laccase (Lac) which enables these organisms to mineralise lignin and a broad range of intractable aromatic xenobiotics. The biodegradation of the highly coloured NOM concentrate obtained from the regeneration of magnetic anion exchange resin (MIEX™) by the white rot fungus Trametes versicolor ATCC 7731 was investigated.
Degradation of NOM was monitored via absorbance and high performance size exclusion chromatography. Decreases of 73% and 55% in colour (A₄₄₆) and UV-absorbing compounds (A₂₅₄), respectively, and molecular weight, by T. versicolor in NOM solution (100 mg C 1^-1) was accompanied by high Lac and MnP activity. Degradation increased with NOM concentration up to 600mg C 1^-1, with inhibition occurring at higher concentrations, and Lac was identified as the major enzyme responsible for NOM degradation. Using filtered extracellular culture fluid, the optimum conditions for NOM degradation were pH 4.5 and 50°C, and different ratios of A₂₅₄/A₄₄₆ for NOM remaining in solution suggest that different bonds were broken by Lac at different pH and temperatures.