Abstract:
A number of white rot fungi were surveyed and collected from different habitats in Thailand in order to screen for a high laccase activity with thermotolerant strain. Of 42 fungi collected from 12 provinces in Thailand, purified mycelia were successfully obtained from 20 fungal samples in which 19 of them showed positive results for laccase production using ABTS agar plate assay. Isolates CU07 and SM10 were found to be thermotolerant and CU07 showed the highest laccase activity (0.363±0.12 U/mL) after incubation for 8 day, at 30°C. This isolate was identified as Trametes polyzona base on its morphological characteristics and Internal Transcribed Spacer (ITS) sequences. T. polyzona CU07 was immobilized on diatomaceous earth and applied for removal of Chemical Oxygen Demand (COD), color and turbidity of black liquor combined with coagulation process. The initial (COD), color and turbidity of black liquor were 292,216 mg/L, 873,777 Platinum-Cobalt unit, and 1330 NTU, respectively. Using coagulation, COD, color and turbidity were removed around 99.18%, 99.20% and 70% respectively, when using 7 mL mixture of chitosan and cation-polyacylamide at weight ratio 1:1, pH was kept constant at 3 (stirred at 140 rpm for 12 min and precipitated for 60 min). The coagulated black liquor was then decolorized using immobilized T. polyzona. The optimal condition for its decolorization was obtained by supplementation of 3.00 w/v glucose and 0.11 w/v ammoniumchloride at pH 6.0. The immobilized T.polyzona could be reused up to 4 cycles. By using this process, the final COD color and turbidity were 1,467 mg/L (99.5% removal), 1,517 Pt-Co unit (99.8% removal) and 266 NTU (80%removal), respectively.