Insight into the high-pressure CO2 pre-treatment of sugarcane bagasse for a delivery of upgradable sugars

Highlights: • CO₂-based pre-treatment provides more sustainable technology of biomass valorisation. • CO₂/H₂O pre-treatment causes enhanced hydrolysis of hemicellulose. • Improved enzymatic yield of leftover produced with high-pressure CO₂. • CO₂ demonstrates chemical and physical effects on biomass processing. This work provides an insight into sugarcane bagasse pre-treatment carried out with greener and more sustainable CO₂/H₂O system. Temperatures and residence times at a fixed initial CO₂ pressure were studied to verify their effects on pre-treatment efficiency with regard to the chemical composition of both water-soluble and water-insoluble fractions as well as to the susceptibility of the latter to enzymatic hydrolysis at high total solids. Also, trends in enzymatic hydrolysis were analysed in function of biomass crystallinity. This work provides an integrated approach in the analysis of upgradable sugars that are released as a result of pre-treatment and enzymatic hydrolysis. At optimal pre-treatment conditions, 17.2 g⋅L⁻¹ sugars were released in the water-soluble fraction mainly as pentoses in monomeric and oligomeric forms. The enzymatic hydrolysis of solids produced at these pre-treatment conditions gave 76.8 g⋅L⁻¹ glucose in the substrate hydrolysate. The overall sugar yield delivered in both pre-treatment and enzymatic hydrolysis was 73.9 mol%. These results were compared to the chemical effect of hydrothermal and/or physico-chemical effects of N₂-aided hydrothermal processes and showed that the greener processing of biomass pre-treatment with CO₂ is advantageous for the integrated valorisation of industrial residues and delivery of upgradable sugars within the biorefinery concept.