Study on the chemical modification of alkali lignin towards for cellulase adsorbent application

The research of cost-efficient lignin-based adsorbents is a practical strategy for the recovery of cellulase. In this study, alkali lignin was modified to increase the phenolic hydroxyl (Ph-OH) content for cellulase adsorption applications. After phenolation, compared with the lignin reference, the maximum adsorption cellulase capacity of lignoresorcinol (LigR) and lignopyrogallol (LigP) was improved from 76.5 mg/g to 842.1 mg/g and 911.4 mg/g, respectively. The enzyme activity of the adsorbed cellulase on LigR was higher than that on LigP, which could migrate to the fresh substrates during enzymatic hydrolysis. The adsorbed cellulase could be easily recovered from two lignin-based adsorbents by adjusting pH. The distinct cellulase adsorption behavior of two lignin-based adsorbents was closely related to the high Ph-OH contents and low S/G ratio in phenolated lignin samples characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Heteronuclear Single Quantum Coherence-Nuclear Magnetic Resonance (HSQC-NMR).

Separation of lignocresol from eucalyptus lignocresol-cellulase complex using organic solvents

A functional lignin-based material, lignocresol, was synthesized from eucalyptus wood meal by using phase separation treatment with p-cresol and 72% sulfuric acid. Lignocresol physically adsorbs Trichoderma reesei cellulase and functions as an immobilized cellulase. Lignocresol-immobilized cellulase was treated with acetone or ethanol to separate the enzyme and its support. Most lignocresol was dissolved in organic solvents and then precipitated in diethyl ether. The recovery yield of lignocresol using acetone was 85% and that using ethanol was 72%, with very low or negligible residual cellulase. Lignocresol is an innovative recyclable enzyme support that can be easily separated using only organic solvents after deactivation of the immobilized enzyme.

Behavior of lignin-binding cellulase in the presence of fresh cellulosic substrate

A model lignin-binding cellulase was prepared from Trichoderma reesei cellulase and lignocresol, which was synthesized from softwood or hardwood lignin. Filter paper was incubated with the lignocresol-cellulase complex, and it was observed that only a limited amount of cellulase migrated to the filter paper. The cellulase adsorption isotherms for the lignocresols and filter paper were fitted to a Langmuir absorption model, and the determined Langmuir constants were as follows: softwood lignocresol>hardwood lignocresol>>filter paper. The calculations demonstrated that lignin-binding cellulase can potentially be recovered by the addition of a sufficient quantity of cellulosic substrate. As a result, the lignocresol-binding cellulase is highly stable and lignocresol can potentially be used for immobilizing cellulase in the active state.