The Accessible Cellulose Surface Influences Cellulase Synergism during the Hydrolysis of Lignocellulosic Substrates

Abstract

Effective enzymatic hydrolysis of insoluble cellulose requires the synergistic action of a suite of cellulase components. Most previous studies have only assessed cellulase synergism on model cellulosic substrates. When the actions of individual and combinations of cellulases (Cel7A, Cel6A, Cel7B, Cel5A) were assessed on various pretreated lignocellulosic substrates, Cel7A was shown to be the major contributor to overall cellulose hydrolysis, with the other enzymes synergistically enhancing its hydrolytic efficiency, at least partially, by facilitating Cel7A desorption (assessed by a double-sandwich enzyme-linked immunosorbent assay). When the influences of various substrate physicochemical characteristics on the effectiveness of enzyme synergism were assessed, a strong relationship was observed between cellulose accessibility (as determined by the cellulose binding module technique) and the degree of synergism, with greater synergy observed on the more disorganized/accessible cellulose surface.

Improvement of ethanol production from crystalline cellulose via optimizing cellulase ratios in cellulolytic Saccharomyces cerevisiae

“…To degrade cellulose into glucose, the cooperative actions of BGL, EG, and CBH are required. According to an endo-exo synergistic model of free-form cellulase, the EG:CBH ratio should be lower than 1; CBH is the major contributor to cellulose hydrolysis, with EG synergistically enhancing hydrolytic efficiency of CBH (Hu et al, 2015). This analysis is consistent with the phenomenon observed in nature, where the cellulase mixture from T. reesei is composed of 60% CBH1 and 12% EG2 (Zhang and Lynd, 2004).…”

“…According to an endo-exo synergistic model of free-form cellulase, the EG:CBH ratio should be lower than 1; CBH is the major contributor to cellulose hydrolysis, with EG synergistically enhancing hydrolytic efficiency of CBH (Hu et al, 2015). According to an endo-exo synergistic model of free-form cellulase, the EG:CBH ratio should be lower than 1; CBH is the major contributor to cellulose hydrolysis, with EG synergistically enhancing hydrolytic efficiency of CBH (Hu et al, 2015).…”

Limitation of cellulose accessibility and unproductive binding of cellulases by pretreated sugarcane bagasse lignin

“…Alkaline pretreatments are more efficient in lignin removal, substantially increasing cellulose digestibility, even after removing only part of the lignin [13–15]. Since most of the hemicellulose remains in the solid fraction, accessory enzymes (xylanases, esterases, and some oxidases) are necessary in the enzyme mixture [16, 17]. …”

Carbon Materials as Phase‐Transfer Promoters for Obtaining 5‐Hydroxymethylfurfural from Cellulose in a Biphasic System

“…[3] 5-Hydroxymethylfurfural (5-HMF) is considered to be amongt he most relevanto nes, with many interesting valorization routes as buildingb lock for the productiono fp olymers (biopolyester building blocks), fuel additives (2,5-dimethylfuran, 5-ethoxymethylfurfural, ethyl levulinate, etc. [5] However,t he high sensitivity of these technologies, as well as their high cost, limit their industrial implementation.T herefore, chemical hydrolysisi sn owadays in the spotlight as ap romisinga lternative to the enzymatic route. [4] 5-HMF production from cellulose requires two main steps, as summarized in Figure 1: (1) hydrolysis of cellulose towards glucose;a nd (2) glucose dehydration to produce 5-HMF.…”

“…The hydrolysis can be enzymatically catalyzed. [5] However,t he high sensitivity of these technologies, as well as their high cost, limit their industrial implementation.T herefore, chemical hydrolysisi sn owadays in the spotlight as ap romisinga lternative to the enzymatic route. Severe conditions in terms of pressure and temperature as well as the use of mineral acids such as HCl and H 2 SO 4 with Brønsted acid sites are widespread.…”