Morphology and laccase production of white-rot fungi grown on wheat bran flakes under semi-solid-state fermentation conditions

In this paper, we studied the laccase production and the growth morphology of different white-rot fungi, i.e. Pleurotus ostreatus, Trametes pubescens, Cerrena unicolor and Trametes versicolor, cultured under semi-solid-state fermentation conditions using wheat bran flakes as a natural low-cost support substrate. Trametes versicolor exhibited the highest laccase activity per gram of total dry matter, followed by P. ostreatus (63.5 and 58.2 U g-1, respectively). In addition, they showed a time profile of laccase production that was quite similar. Growth morphology was studied using environmental microscopic images and analyzed by discrete Fourier transformation-based software to determine the mean diameter of the hyphae, the number of hypha layers and the global micromorphology. The four strains exhibited different micromorphologies of growth. Pleurotus ostreatus presented narrow hyphae, which formed many thick clumps, T. pubescens and T. versicolor showed clumps of different sizes and C. unicolor showed thick hyphae that formed larger clumps, but in less amounts.