Supercritical Fluids: A Promising Technique for Biomass Pretreatment and Fractionation

Abstract

Lignocellulosic biomasses are primarily composed of cellulose, hemicelluloses and lignin and these biopolymers are bonded together in a heterogeneous matrix that is highly recalcitrant to chemical or biological conversion processes. Thus, an efficient pretreatment technique must be selected and applied to this type of biomass in order to facilitate its utilization in biorefineries. Classical pretreatment methods tend to operate under severe conditions, leading to sugar losses by dehydration and to the release of inhibitory compounds such as furfural (2-furaldehyde), 5-hydroxy-2-methylfurfural (5-HMF), and organic acids. By contrast, supercritical fluids can pretreat lignocellulosic materials under relatively mild pretreatment conditions, resulting in high sugar yields, low production of fermentation inhibitors and high susceptibilities to enzymatic hydrolysis while reducing the consumption of chemicals, including solvents, reagents, and catalysts. This work presents a review of biomass pretreatment technologies, aiming to deliver a state-of-art compilation of methods and results with emphasis on supercritical processes.

Material utilization of green waste: a review on potential valorization methods

“…1 Components of lignocellulose. Chemical structures of cellulose (a), the lignin building blocks coniferyl alcohol, p-coumaryl alcohol, and sinapyl alcohol (b) as well as hemicellulose from grass (c) adapted from Escobar et al (2020) concentrations of cellulose and hemicellulose, than leaves (Jung et al 2015). At the same time, leaves contain a higher amount of extractives (Jung et al 2015).…”

Advances in Pretreatment of Straw Biomass for Sugar Production

“…Carbon dioxide, ammonia, water, and hydrocarbons (propane and butane) are the most common supercritical fluids. Supercritical carbon dioxide (Sc-CO 2 ) is one of the most popular utilized compressed fluids for lignocellulose feedstock processing attributed to generate no byproducts without requiring any separation process (Escobar et al, 2020). Moreover, Sc-CO 2 is based on the application of CO 2 as a supercritical fluid.…”

“…Other supercritical fluid approaches such as supercritical ammonia and supercritical ethanol are also employed in the area of biomass fractionation and conversion. In addition, in comparison with subcritical ethanol, the supercritical ethanol pretreatment exhibited higher lignin fractionation and higher purity and stability of cellulose (Escobar et al, 2020). Then, the water present in lignocellulosic feedstocks coupled with carbon dioxide produces carbonic acid, which could facilitate the efficiency of hemicellulose degradation (Daza Serna et al, 2016;Fockink et al, 2018).…”

Strategies to Increase the Biological and Biotechnological Value of Polysaccharides from Agricultural Waste for Application in Healthy Nutrition

“…Other techniques are being investigated for the modification of polysaccharides, such as cold plasma processing [ 154 , 155 ], pulsed electric field processing [ 156 ], high pressure [ 83 ], high-pressure UAE [ 157 , 158 ], supercritical fluids [ 159 , 160 ] and degradation with ascorbic acid [ 161 , 162 ].…”