Enhancing Effect of Residual Lignins from D. Sinicus Pretreated with Fenton Chemistry on Enzymatic Digestibility of Cellulose

Abstract

To screen and evaluate possible functional factors in the bamboo lignin moiety that could block non‐productive adsorption of enzyme proteins on lignin, milled wood lignin (MWL) and Fenton oxidized lignin (FOLs) were prepared and incorporated in the enzymatic hydrolysis of Avicel. The addition of MWL decreased the 72 h glucose yields of cellulose from 57.1 % to 45.3 %, while FOLs effectively improved the enzymatic digestibility up to 69.5 %, which was 22 % higher than the system without the use of FOLs. The adsorption affinity and binding strength of cellulase with FOLs were lower than that with MWL. After Fenton pretreatment, hydrophilicity of lignins increased due to formation of C−O− and O−C=O bonds. Furthermore, high surface negative charges on FOLs resulted in strong electrostatic repulsion against the negatively charged cellulases. Finally, analysis of FOLs with 13C and 2D‐HSQC NMR indicated that the cleavage of β‐O‐4 linkages and demethoxylation occurred, and that less condensed structures at the Cβ and Cγ positions were observed. These oxidation reactions of the bamboo lignin lead to the formation of functional factors to alleviate irreversible adsorption of cellulase onto FOLs, and thus were responsible for promoting enzymatic digestibility efficiency.

Effect of alkaline lignin modification on cellulase–lignin interactions and enzymatic saccharification yield

“…Sodium sulfite of 2 g was mixed with the above solution to carry out sulfonation reaction at 95 °C and 3 h [ 36 ]. Oxidized Lignin (OL) was prepared based on the Fenton oxidation reaction reported in previous literature [ 37 , 38 ]. In brief, AL (5 g) was dissolved in 100 mL deionized water with a little NaOH at 50 °C and the pH was adjusted to 3–5.…”

Effect of Pretreatments on the Enzymatic Hydrolysis of High-Yield Bamboo Chemo-Mechanical Pulp by Changing the Surface Lignin Content

“…CTMP fibers were deeper in color than the APMP and SCMP fibers, which may be related to more lignin on the surface of CTMP fibers. After hydrogen peroxide and ethanol pretreatments, the color of the APMP, SCMP, and CTMP fibers became lighter, while the color of the APMP, SCMP, and CTMP fibers became deeper after Fenton pretreatment, possibly due to the highly active hydroxyl free in the Fenton reagent-oxidized lignin to generate the additional carbonyl structure [ 23 ], and to form more chromophoric groups, and, therefore, the fiber color became deeper [ 24 ].…”