Integrating the coproduction of cellulose nanofibers and biobutanol from eucalyptus pulp using an environmentally friendly process

Abstract

The combination of enzyme-mediated pretreatment with mechanical fibrillation has become an environmentally friendly and low-energy strategy to extract cellulose nanomaterials (CNM) from lignocellulosic biomass. The use of hydrolytic enzymes to produce CNM allows the coproduction of sugars that can be further converted to biofuels and/or value-added products. This work evaluated the integration of biobutanol production via fermentation of sugars released at high solid concentration with the biochemical platform of cellulose nanofibers (CNF) production. Cellulose fibers were partially hydrolyzed at low enzyme loadings (5 FPU/gsolid) and high solid concentrations (4-16%) obtaining a separate sugar stream (50 g/L), which was completely converted to biobutanol and coproducts (up to 15 g/L) by Clostridium beijerinckii strains. The cellulosic residue was mechanically defibrillated by ball milling to produce CNF (4-14 nm width, 220-230 aspect ratio). The enzyme fractionation represents a promising strategy to integrate the coproduction of CNF and biobutanol from cellulosic pulp.