Effect of culturing processes and copper addition on laccase production by the white-rot fungusFomes fomentariusMUCL 35117

Abstract

To produce high laccase activities from the white-rot fungus Fomes fomentarius. Different culturing methods, viz, cell immobilization on stainless steel sponges and plastic material and solid-state fermentation (SSF) using wheat bran as substrate were used for laccase production by the white-rot fungus F. fomentarius. The SSF study expresses the highest laccase activities, nearly to 6400 U l(-1) after 13 days of laboratory flasks cultivation. When the wheat bran medium was supplemented with 2 mmol l(-1) copper sulfate, laccase activity increased by threefold in comparison to control cultures, reaching 27 864 U l(-1). With the medium thus optimized, further experiments were performed in a 3 l fixed-bed bioreactor (working volume 1.5 l) leading to a laccase activity of about 6230 U l(-1) on day 13. The results obtained clearly showed the superiority of wheat bran for laccase production over stainless steel sponges and plastic material. Supplementing the wheat bran solid medium with 2 mmol l(-1) copper sulfate allowed obtaining high activities at flask scale. The system was scaled to fixed-bed laboratory reactor. The high enzyme production along with the low-cost of the substrate, showed the suitability of the system F. fomentarius- SSF for industrial purposes.