Enzymatic digestibility of lignocellulosic wood biomass: Effect of enzyme treatment in supercritical carbon dioxide and biomass pretreatment

Pawan Kumar; Azadeh Kermanshahi-Pour; Satinder Kaur Brar; Chunbao Charles Xu; Quan Sophia He; Sara Evans; Jan K Rainey

doi:10.1016/j.heliyon.2023.e21811

Enzymatic digestibility of lignocellulosic wood biomass: Effect of enzyme treatment in supercritical carbon dioxide and biomass pretreatment

Heliyon. 2023 Oct 31;9(11):e21811. doi: 10.1016/j.heliyon.2023.e21811. eCollection 2023 Nov.

Authors

Pawan Kumar¹, Azadeh Kermanshahi-Pour¹, Satinder Kaur Brar², Chunbao Charles Xu³, Quan Sophia He⁴, Sara Evans⁵, Jan K Rainey^{5

6}

Affiliations

¹ Biorefining and Remediation Laboratory, Department of Process Engineering and Applied Science, Dalhousie University, Halifax, Nova Scotia B3 J 1Z1, Canada.
² Department of Civil Engineering, Lassonde School of Engineering, York University, North York, Toronto, Ontario M3J 1P3, Canada.
³ School of Energy and Environment, City University of Hong Kong, Hong Kong SAR, Hong Kong.
⁴ Department of Engineering, Faculty of Agriculture, Dalhousie University, Truro, Nova Scotia B2N 5E3, Canada.
⁵ Department of Chemistry, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
⁶ Department of Biochemistry & Molecular Biology and School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.

Abstract

Energy and resource intensive mechanical and chemical pretreatment along with the use of hazardous chemicals are major bottlenecks in widespread lignocellulosic biomass utilization. Herein, the study investigated different pretreatment methods on spruce wood namely supercritical CO₂ (scCO₂) pretreatment, ultrasound-assisted alkaline pretreatment, and acetosolv pulping-alkaline hydrogen peroxide bleaching, to enhance the enzymatic digestibility of wood using optimized enzyme cocktail. Also, the effect of scCO₂ pretreatment on enzyme cocktail was investigated after optimizing the concentration and temperature of cellulolytic enzymes. The impact of scCO₂ and ultrasound-assisted alkaline pretreatments of wood were insignificant for the enzymatic digestibility, and acetosolv pulping-alkaline hydrogen peroxide bleaching was the most effective pretreatment that showed the release of total reducing sugar yield (TRS) of ∼95.0 wt% of total hydrolyzable sugars (THS) in enzymatic hydrolysis. The optimized enzyme cocktail showed higher yield than individual enzymes with degree of synergism 1.34 among the enzymes, and scCO₂ pretreatment of cocktail for 0.5-1.0 h at 10.0-22.0 MPa and 38.0-54.0 °C had insignificant effect on the enzyme's primary and global secondary structure of cocktail and its activity.

Keywords: Biomass pretreatment; Cellulase; Enzymatic hydrolysis; Enzyme pretreatment; Fermentable sugars; Lignocellulosic biomass; Supercritical CO2.