Enhancing the enzymatic digestibility of sugarcane bagasse through the application of an ionic liquid in combination with an acid catalyst

Abstract

Various ionic liquids have been identified as effective pretreatment solvents that can enhance the cellulose digestibility of lignocellulose by removing lignin, one of the main factors contributing to the recalcitrant nature of lignocellulose. 1-Butyl-3-methylimidazolium methylsulfate ([BMiM]MeSO(4)) is a potential delignification reagent, hence its application as a pretreatment solvent for sugarcane bagasse (SB) was investigated. The study also evaluated the benefit of an acid catalyst (i.e., H(2) SO(4)) and the effect of pretreatment conditions, which varied within a time and temperature range of 0-240 min and 50-150°C, respectively. The use of an acid catalyst contributed to a more digestible solid and a higher degree of delignification. However, the [BMiM]MeSO(4)-H(2) SO(4) combination failed to produce a fully digestible solid, as a maximum cellulose digestibility of 77% (w/w) was obtained at the optimum pretreatment condition of 125°C for 120 min. Furthermore, up to half of the lignin content could be extracted during pretreatment, while simultaneously extensive, sometimes complete, removal of xylan, the presence of which, also hampers cellulose digestibility. Hence, [BMiM]MeSO(4) has been identified an effective pretreatment solvent for SB as the application thereof both significantly improved digestibility, and simultaneously removed two of the main factors contributing to the recalcitrant nature of lignocellulose. As xylan and lignin have potential value as precursor chemicals, the existing process may in future be extended toward substrate fractionation, a biorefinery concept where value is added to all feedstock constituents.

Sugarcane and Woody Biomass Pretreatments for Ethanol Production

“…However, in pretreatment of sugarcane bagasse catalyzed by acid, using HCl- [Bmim] [Cl] [132] [133], cellulose crystallinity remained unaltered even though a significant increase of cellulose digestibility was achieved. The authors suggested that digestibility increase was due to the highly effective and simultaneous removal of xylan and lignin that facilitated cellulose enzymatic saccharification efficiency.…”

Pretreatment of Japanese cedar by ionic liquid solutions in combination with acid and metal ion and its application to high solid loading

“…This result indicated that acid pretreatment in IL was superior to conventional acid pretreatment in water. According to previous study [21], below the glass transition temperature of lignin (<160°C), a digestible biomass was slightly produced in the absence of IL. Therefore, we believe the absence of an IL caused the low production of glucose.…”

“…Aqueous ionic liquid pretreatment solvent with two catalysts Acid-catalyzed pretreatment in IL has usually been combined with at least one kind of acid for improvement [19][20][21]. On the other hand, in the case of diluted acid pretreatment for the biomass in a water system, several studies have shown that inorganic salts also indicate the possibility of improvement for the hydrolysis rate of the hemicellulose and cellulose in biomass [22,23].…”

“…Recently, it was reported that a small amount of acid has a positive effect on the degradation of biomass in the presence of ILs and significant amounts of water [19][20][21]. Existing research has dictated that biomass pretreatments required the selective removal of lignin and hemicellulose from cellulose, in other words, 'biomass fractionation'.…”

Fruit waste streams in South Africa and their potential role in developing a bio-economy

“…Pretreatment of different agricultural residues, with the aid of a 15-L reactor steam gun, has been evaluated with South African sponsored research funding in anticipation of an emerging cellulosic ethanol industry. [115][116][117][118] Researchers have also developed the capacity to generate pyrolysis and gasification products from different cellulosic feedstocks to substitute fossil fuels such as coal, coking coal and reductants. 119,120 These studies also support developments toward the realisation of a bio-economy.…”