Rheological investigation of complex lignocellulosic suspensions during hydrolysis using pure and cocktail of enzymes

Enzymatic hydrolysis of lignocellulosic materials at high dry matter content is of crucial interest in bioindustry, and namely for biorefinery. Physical limitations linked to high concentrations must be understood and surpassed. This study used online and in-situ measurements to examine the rheological properties of different cellulosic suspensions and its evolution during enzymatic hydrolysis. Semi-dilute conditions were used to introduce non-Newtonian rheological behaviors while limiting complexity. For all suspensions, the relationship between shear-thinning behavior versus substrate concentration was modeled. During enzymatic digestion using single and cocktails of cellulolytic activities, the evolution in shear-thinning properties was finely quantified. The viscosity-time relationship during hydrolysis was accurately described through first-order kinetics, and a unique, dimensionless representation was obtained. The critical concentrations indicating a shift from diluted to concentrated regime and the viscosity reduction kinetics that were identified should provide a strong foundation for defining an optimal substrate feed rate for fed-batch and continuous processes.