Abstract

Abdelhafidh Dhouib , Manel Hamza , Hela Zouari , Tahar Mechichi , Rafik H

This work represents the first report on the ability of autochthonous fungi of Tunisia to produce ligninolytic enzymes. Three hundred fifteen fungal strains were isolated from different Tunisian biotopes. These fungal strains were first screened for lignin -modifying enzymes on solid media containing Poly R- 478 or ABTS. Of the 315 tested strains, 49 exhibited significant ABTS-oxidation activity, expressed within the first week of incubation and only 18 strains decolourised the Poly R-478. These positive strains were further screened in liquid culture and laccase, and lignin and Mn2+ - oxidizing peroxidases activities were assayed. Of the 67 strains grown on liquid medium, 28 produced at least one of these 3 enzymes. The 8 highest producers of ligninolytic activities were identified by molecular techniques and 3 among them produced Lac, MnP and LiP simultaneously. New isolates reported in this work as fungi with significant ligninolytic activities includes Oxyporus, Stereum and Trichoderma. The isolated Trametes trogii CTM 10156 was the best Lac producer. Culture conditions and medium composition were optimised for this strain and resulted in high Lac production of 110 U ml1 within 15 days of incubation (367 times higher than control medium).