Production of Trametes versicolor laccase by solid state fermentation using a fixed-bed bioreactor

The aim of this work was to investigate the production of Trametes versicolor laccase by SSF (solid state fermentation) using a fixed-bed bioreactor. The SSF optimization assays were carried out in Erlenmeyer flasks (250 mL) containing 12.5 g of dried wheat bran. The medium moisture (50, 60, 70, 80 and 90% w/w), inoculum (78, 240, 400, 560 and 720 mycelium plugs/kg D.M.- dried matter) and the contents of glucose (0, 10, 30, 50 and 70 g/kg D.M.), yeast extract (24 and 48 g/kg D.M.) and CuSO4 (2.4 and 4.8 g/kg D.M.) were evaluated for laccase production. After this optimization an experiment in a fixed-bed bioreactor (250 mL) with 25g D.M. of wheat bran was accomplished, and this reactor was aerated (1.5 L/min) with humidified air. The laccase activity was quantified using ABTS as substrate. The results of the experiments demonstrated that the moisture of 70% w/w and the inoculum of 240 mycelium plus/kg D.M. were optimized conditions producing, on the 20th day of the experiment, a laccase activity of 19,341 UI/kg D.M. Glucose, yeast extract and CuSO4, in the experimental conditions, decreased the laccase production. The experiment carried out in the fluidized bed reactor, with the optimized conditions, resulted on the 16th day of experiment in a laccase activity of 18,917 UI/kg D.M. These experiments demonstrated that it was possible to produce high laccase levels using the wheat bran as substrate without any supplementation and that the fluidized bed reactor showed to be adequate for the enzyme production, as well as the Erlenmeyer flasks