Abstract
There is a growing demand for the efficient treatment of seaweed biomass and the production of seaweed-degrading enzymes. Fifteen algicolous fungi were isolated from the Red Sea macroalgae in Egypt and were studied for their capability of utilizing Sargassum and Palisada biomass and subsequent production of different thallus-degrading enzymes. Most of the fungi efficiently saccharified the macroalgal extracts that amounted to more than 70 % of the sugars in the unfermented macroalgal extract. Algicolous fungi fermented Sargassum through extracellular fucoidanases and alginases that were negatively correlated as revealed by principal component analysis (PCA), suggesting an antagonistic degradation of Sargassum polysaccharides. Extracellular agarases resulted in efficient fermentation of Palisada biomass. Fungi expressed also amylase and protease activities that were low or nonexistent and biomass-dependent. Amylase showed positive correlation with agarase as indicated by PCA, which suggests that the two enzymes synergistically degrade Palisada biomass. The enzymatic cocktails were also able to release reducing sugars from the powdered macroalgal thalli, indicating the importance of enzymes in the saprophytic growth of fungi. Generally, enzymatic activities and specific activities of fucoidanase, alginase, and agarase in algicolous fungi were higher than reported previously for non-algicolous fungi. Enzymatic activities of the marine brown algal pathogen Lindra thalassiae indicated that infection by this pathogen might occur through alginases. The results shed light into production of less expensive enzymatic mixtures from an understudied group of microorganisms targeting seaweed-degradation. These enzymes have many biotechnological and industrial applications as thallus maceration and protoplast isolation despite bioactivity of obtained oligosaccharides.