Lignin fractionation to realize the comprehensive elucidation of structure-inhibition relationship of lignins in enzymatic hydrolysis

Elucidating the nonproductive adsorption mechanism of cellulase with lignin fractions from hydrothermally pretreated poplar using multi-dimensional spectroscopic technologies

“…At each pretreatment temperature, the β-O-4, β–β, and β-5 linkage contents of SL are significantly lower than those of RL, suggesting that SL has undergone more depolymerization than RL. 21 Therefore, lignin β-O-4 was fractured in an acidic environment, and the partially dissolved lignin fragments condensed with carbohydrates in a pretreatment solution again to form SL with small molecular weight. In addition, the content of the linkage bonds (β-O-4, β–β) decreased with increasing pretreatment temperature for both SL and RL.…”

“…These forces are difficult to quantify individually and can be affected by several factors (temperature, pH, and ionic strength). 20,21,66 In the process of lignin and cellulase interactions, ΔH and ΔS values can provide insights into the relative contribution of different forces to the overall interaction (entropy change (ΔS), free energy change (ΔG), and enthalpy change (ΔH) following eqn (S3)-(S5)). For example, if the interaction between lignin and cellulase is primarily driven by hydrogen bonding, the ΔH value is negative, indicating that energy is released during the formation of the bond.…”

“…[16][17][18][19] For example, Lou et al 20 discovered that an increased pH value significantly enhances the surface negative charge of lignin, leading to increased hydrophilicity of lignin and reduced binding affinity with cellulase enzymes. Lai et al 21 isolated two lignin fractions (ethanol-soluble and ethanol-insoluble lignin) from different pretreated poplar wood and found that lignin heterogeneity, condensed aromatic units, and phenolic hydroxyl content are critical factors determining lignin's inhibitory effects on enzymatic hydrolysis. Jia et al 16 discovered that with the increasing severity of hydrothermal pretreatment, the β-O-4 linkages of the lignin deposited on the wood chips decreased whereas the S/G ratio increased.…”

“…In recent years, the influence of re-deposited lignin on enzyme hydrolysis has been investigated by Koo et al , 22 Hansen et al , 23 and Wu et al , 24 who identified that this type of surface lignin was the significant obstacle for the decrease in enzyme hydrolysis rate. Lai et al 21 and He et al 25 observed that the nonproductive adsorption of cellulase enzymes onto lignin is influenced not only by the physicochemical properties of lignin and its content in biomass but also by its distribution. During the pretreatment process, the redeposit lignin on the surface of biomass can also be reacted with carbohydrate byproducts, resulting in the formation of pseudo-lignin.…”

Integrated Nondestructive Spectroscopic Technology to Reveal the Influence Mechanism of Lignins from Pretreated Corn Stover on Cellulose Saccharification

“…Consequently, this causes the enzymatic hydrolysis of the pretreated solid matrix to occur less efficiently. A growing body of research has revealed that the lignin’s nonproductive adsorption onto cellulase is not only influenced by its physical and chemical properties and its content in the pretreated material but, most importantly, by the lignin’s distribution. ,, To further elucidate the lignin’s distribution in pretreated materials and distinguish residual lignin, herein, these soluble lignin, deposited lignin, and pseudolignin of pretreated biomass are collectively defined as “surface lignin” (SL) . While in-depth research into the adsorption mechanisms of lignin from pretreatment and cellulase continues to progress, the debate persists concerning the different contributions of lignin’s distribution to the ultimate cellulase’s adsorption behavior.…”