Cellulose fibers deconstruction by twin-screw extrusion with in situ enzymatic hydrolysis via bioextrusion.

The aim of this work was to study the cellulose fibers deconstruction by twin-screw extrusion with in situ enzymatic hydrolysis via bioextrusion, for cellulose nanofibrils (CNF) production. Cellulose pulp was extruded with an optimized screw profile, with or without (reference) the addition of an enzymatic solution. An increase of crystallinity index from 67.0% to 73.7% and decrease of DP from 1003 to 419 were observed with bioextrusion. Direct activity measurements of the enzyme confirmed its activity during the process (sugar content increasing from 0.07 ± 0.004 to 2.38 ± 0.003 mg/mL) and after the process (specific activities around 0.20 CMCU/mL). Enzymes were not deactivated during bioextrusion and could be recycled. CNF properties were higher with bioextrusion compared to reference (respective quality indices of 55.5 ± 2.7 and 39.8 ± 2.8), with a lower energy consumption. This proof of concept could be optimized for the industrial production of highly concentrated CNF.

Enzymatic hydrolysis of corn crop residues with high solid loadings: New insights into the impact of bioextrusion on biomass deconstruction using carbohydrate-binding modules.

Lignocellulosic biomass is a sustainable source of renewable substrate to produce low carbon footprint energy and materials. Biomass conversion is usually performed in two steps: a biomass pretreatment for improving cellulose accessibility followed by enzymatic hydrolysis of cellulose. In this study we investigated the efficiency of a bioextrusion pretreatment (extrusion in the presence of cellulase enzyme) for production of reducing sugars from corn crop agricultural residues. Our results demonstrate that bioextrusion increased the reducing sugar conversion yield by at least 94% at high solid/liquid ratio (14%-40%). Monitoring biomass surface with carbohydrate-binding modules (FTCM-depletion assay) revealed that well known negative impact of high solid/liquid ratio on conversion yield is not due to the lack of exposed cellulose which was abundant under such conditions. Bioextrusion was found to be less efficient on alkaline pretreated biomass but being a mild and solvent limiting pretreatment, it might help to minimize the waste stream.