Challenges in cellulolytic enzyme production by filamentous fungus Trichoderma reesei on cellulosic materials

Conference poster, 2012

Cellulose is the most abundant renewable and biodegradable material on earth, therefore researchers have a great interest in development of cellulose based sustainable energy industry and production of value-added products. Enzymatic hydrolysis of cellulose by cellulolytic enzymes is an essential step in the biomass-to-biofuels and biochemicals process. Some filamentous fungi use cellulose as a nutrient source for their growth and in turn they produce cellulolytic enzymes. The industrial cellulase production is dominated by the filamentous fungus Trichoderma reesei [1]. The use of cellulosic substrates instead of lactose and other expensive substrates, currently employed in industry for cellulolytic enzyme production, would significantly reduce the cost of the process. However, enzyme productivities are significantly lower on cellulose than on lactose. We studied the enzyme production by T. reesei Rut C-30 on the model and industrial cellulosic substrates. Industrial substrates have a high content of cellulose but also contain residual hemicellulose, lignin and some inhibitors. The results of our study will bring insight into bottlenecks of enzyme production on cellulose. During the enzyme production study, we grew T. reesei strain Rut C-30 in submerged fermentations on commercial cellulose Avicel PH101 and industrial-like cellulosic substrates from spruce. These substrates were produced during the process of sodium hydroxide cooking, used in pulp and paper industry. The chemical and physical properties of the substrates were characterized by high performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD), gravimetric analysis of lignin and solid-state nuclear magnetic resonance (NMR) technique. We measured protein yields, cellulolytic enzyme activities and examined protein profile. Also, we analyzed the influence of inhibitors on fungal growth and how different substrates affect fungal morphology. Inhibitors, soluble sugars and lignin degradation products did not have any impact on the growth ability of T. reesei Rut C-30 but it did influence the fungal morphology. Industrial-like substrates yielded less enzymes and enzyme adsorption may be one important factor influencing protein yields.