DEGRADATION OF CHLOROPHENOLIC COMPOUNDS BY TRICHODERMA-HARZIANUM ISOLATED FROM LAKE BONNEY, SOUTH-EASTERN SOUTH AUSTRALIA

In a study of the fate of chlorophenolic compounds in Lake Bonney, Sou th-Eastern South Australia, several isolates of the fungus Trichoderma harzianum were assessed for their capacities to metabolize these comp ounds. Lake Bonney receives effluent from two pulp mills, one of which used molecular chlorine for bleaching of pulp between 1966 and Septem ber 1991. Effluent and waters of the lake had previously been found to be contaminated with chlorophenolic compounds, including 2,4,6-trichl orophenol and chloroguaiacols. Isolates of T. harzianum were obtained from lake water samples collected at locations approximately 10 m, 1, 5, and 9 km from the discharge point of effluent to the lake. The capa city of one isolate (no. 1) collected 10 m from the discharge point, w as assessed based on substrate loss in culture media, a corresponding reduction in adsorbable organic halogens (AOX), production of (CO2)-C- 14 from a C-14-labeled chlorophenol, and the release of chloride ions from the dehalogenation of tetrachloroguaiacol. The capacities of seve ral other isolates were briefly assessed based on reductions in concen trations of spiked tetrachloroguaiacol in culture medium and the corre sponding AOX. Trichoderma harzianum (No. 1) mineralized a minor percen tage (2-3%) of spiked radiolabeled pentachlorophenol and partially deh alogenated (46%) spiked tetrachloroguaiacol in mineral salts medium. A ll isolates were found capable of reducing concentrations of tetrachlo roguaiacol in a mineral salts medium and the corresponding AOX. Those with the highest capacities were obtained from locations close to the effluent discharge point to the lake. The presence of this fungus in l ake water may account, in part, for the decline in chlorophenolic comp ounds in Lake Bonney after chlorination at the pulp mill had ceased. ( C) 1997 by John Wiley & Sons, Inc.