Identifying and overcoming the effect of mass transfer limitation on decreased yield in enzymatic hydrolysis of lignocellulose at high solid concentrations

Enhancement and modeling of enzymatic hydrolysis on cellulose from agave bagasse hydrothermally pretreated in a horizontal bioreactor

“…The One-way ANOVA showed that substrate loading is a significant factor (p ≤ 0.05) on the glucose yield reached in the EH of pretreated AGB; while multiple means comparison test performed according to Tukey's criteria indicated that 10 and 15% (w/v) solids loading presented no significant difference on the cellulose to glucose conversion yield achieved at 72 h. The reduction on the saccharification efficiency has been previously reported as a result of the high viscosity of the slurry that limits the mass transfer and hinders the enzyme-substrate interactions (Pino et al, 2018). The presence of lignin is another possible factor that hinder the saccharification by acting as a physical barrier for cellulases to access cellulose, inducing non-productive linkage and adsorption of the enzyme into lignin's surface (Du et al, 2017). Furthermore, feedback inhibition has been widely reported as one of the main obstacles restricting enzymatic hydrolysis improvement at high solid concentrations (Andrić et al, 2010).…”

“…The substrate loading of 1% (w/v) presented the highest glucose production rate constant, while 30% (w/v) corresponded to the lowest one. This behavior can be attributed to the greater viscosity of the cellulosic substrate at high solid concentrations, which produced mixing and diffusion difficulties and could have led to an augmented non-specific adsorption of cellulases onto lignin (Du et al, 2017). Additionally, the retained cellulase activity was calculated according to Eq.…”

“…The results demonstrated that the fed-batch mode produced a betterment of the enzymatic hydrolysis at high solid loadings. Du et al (2017) studied substrate feeding and simultaneous substrate and enzyme feeding at solid concentrations of 10, 15 and 20% (w/v) dry matter. The authors reported a cellulose conversion enhancement with the solid loading increment.…”

“…Horizontal bioreactors have been stated as a promising alternative to enhance high solid loading enzymatic hydrolysis (Dasari, Dunaway, & Berson, 2009;Du et al, 2014). Du et al (2017) reported that, among different strategies, horizontal rotating bioreactors were the most effective alternative to assure an adequate mixing between solid substrate and enzyme in the EH performed at high solid loadings.…”

Production of Oligosaccharides from Agrofood Wastes

“…Substrate particle size affects the overall rate of the hydrolysis process [96], given that this size impacts upon the efficiency of the substrate access of the enzymatic mixture, introducing mass transfer limitations in bigger particles. In addition, high solid presence in the reaction medium, an industrial tendency, increases viscosity and also affects the external and the internal mass transfer rate [97,98].…”