الخلاصة:
51 fungal isolates were isolated from forests in eastern Algeria (Kenouaâ, Belezma and Chettaba), three of them showed positive laccase activity. The morphological and molecular study carried out allowed identifying them as Trichoderma longibrachiatum, Trametes versicolor and Chaetomium globosum.
The production kinetics of laccase on PDB medium exposed that Chaetomium globosum produced a large amount of laccase after 12 days of fermentation, reaching 550 U / L in Erlens and 987U / L in 20 L fermenter, while Trametes versicolor secretes after 8 days of fermentation 1400 U / L of laccasic activity in Erlens and 833U / L in fermenter (20L).
Furthermore, the laccase activity secreted by Trametes versicolor has been shown to be at its maximum at pH 3 and at 55 ° C., whereas the enzymatic activity produced by Chaetomium globosum reaches its maximum at 35 ° C. and at pH between 5 and 6.
The partial characterization of laccase performed on a Native page gel revealed two different isozymes produced by Trametes versicolor (Lac1 and Lac2) and a single isozyme produced by Chaetomium globosum.
The study of laccase production using waste media showed the ability of Trametes versicolor and Chaetomium globosum to produce laccase on all media tested, however, the optimum of laccase produced by Trametes versicolor (350U / L) and by Chaetomium globosum (400 U / L) is obtained on pumpkin waste medium. According to the literature consulted, this work is the first to use these two fungal strains for the production of laccase using only the pumpkin waste as the exclusive source of carbon.
The study of synthetic dyes degradation carried out on solid medium and on submerged medium, demonstrated that selective strains degrade two dyes effectively: Malachite Green and Congo Red. Degradation was followed by spectrophotometric analysis and HPLC. It was found that 100% decolorization of Congo Red by Trametes versicolor’s laccase was complete after 45 minutes of reaction and Malachite green after 60 minutes. On the other hand, the laccasic extract from Chaetomium globosum allowed a 100% discoloration of Malachite
Green and Congo Red after 55 minutes of reaction. This result can be promising, and considerable progress in the field of biotechnological applications.
The literature consulted did not mention the ability of Chaetomium species to degrade Malachite Green or Congo Red. As a result, this work is considered original.
