Physicochemical Structural Changes of Cellulosic Substrates during Enzymatic Saccharification

Abstract

Enzymatic hydrolysis represents one of the major steps and barriers in the commercialization process of converting cellulosic substrates into biofuels and other value added products. It is usually achieved by a synergistic action of enzyme mixture typically consisting of multiple enzymes such as glucanase, cellobiohydrolase and β-glucosidase with different mode of actions. Due to the innate biomass recalcitrance, enzymatic hydrolysis normally starts with an initial fast rate of hydrolysis followed by a rapid decrease of rate toward the end of hydrolysis. With majority of literature studies focusing on the effect of key substrate characteristics on the initial rate or final yield of enzymatic hydrolysis, information about physicochemical structural changes of cellulosic substrates during enzymatic hydrolysis is still quite limited. Consequently, what slows down the reaction rate toward the end of hydrolysis is not well understood. This review highlights recent advances in understanding the structural changes of cellulosic substrates during the hydrolysis process, to better understand the fundamental mechanisms of enzymatic hydrolysis.

Different pre-treatments and kinetic models for bioethanol production from lignocellulosic biomass: A review

“…The mechanism of cellulose hydrolysis using enzymes is explained briefly with the following basic steps. Diffusion of enzyme from bulk aqueous phase to the surface of substrate Formation of enzyme-substrate complex due to adsorption of enzyme Cellulose breakdown Diffusion of breakdown products into bulk aqueous phase End product glucose formation in the bulk aqueous phase [ 25 ]. …”

“…These repeated tests are required because the influencing factors of enzymatic hydrolysis are numerous and all interconnected (for example, pre-treatment, enzymatic hydrolysis, and substrate characteristics) [ 23 , 24 ]. Raguskas et al have explained the structural changes in cellulosic substrates during enzyme hydrolysis and various substrate and enzyme related factors that influence the conversion process [ 25 ].…”

Promotional effects of water-soluble extractives on bamboo cellulose enzymolysis

“…According to (Gunawan et al 2017), high content of xylan (Table 2) in AL pretreated bamboo was an important factor for relative low cellulase activity. The promotional effect of the extract not only directly correlated to the amount of lignin present in the substrate, but also depend on characteristics of residual lignin and affinity for cellulase adsorption (Meng et al 2016).…”

Enhancing Biogas Production of Co-Digested Cattle Manure with Grass Silage from a Local Farm in Landshut, Bavaria, through Chemical and Mechanical Pre-Treatment and Its Impact on Biogas Reactor Hydraulic Retention Time

“…The primary cell plant walls consist of cellulose, pectin and hemicellulose [6], in which the pectic matrix of polysaccharides entrenches the cellulose bundles together [7]. The secondary walls consist of cellulose, hemicellulose, lignin [6,8] and some proteins, terpenic oils, fatty acids/esters and inorganic materials, mainly based on N, P and K [9]. Hemicellulose and cellulose are available for fermentation to bioenergies after hydrolysis [10].…”