Deconstructing sugarcane bagasse lignocellulose by acid-based deep eutectic solvents to enhance enzymatic digestibility.

Biorefinery with deep eutectic solvent (DES) is an emerging processing technology to overcome the shortcomings of conventional biomass pretreatments. This work evaluates the biorefinery of sugarcane bagasse (SCB) with DES formulated with choline chloride as hydrogen bond acceptor and three hydrogen bond donors: lactic acid, citric acid, and acetic acid. Acetic acid showed unique ionic properties responsible for the selective removal of lignin and the deconstruction of cellulose to improve the digestibility of up to 97.61 % of glucan and 63.95 % of xylan during enzymatic hydrolysis. In addition, the structural characteristics of the polysaccharide-rich material (PRM) were analyzed by X-rays, ATR-FTIR, SEM, and enzymatic hydrolysis, and compared with the original material sample, for a comprehensive understanding of biomass deconstruction using different hydrogen bond donors (HBD) as DES pretreatment.

Morán-Aguilar MG ，Calderón-Santoyo M ，de Souza Oliveira RP ，Aguilar-Uscanga MG ，Domínguez JM ... -  《-》

Improving enzymatic digestibility of sugarcane bagasse from different varieties of sugarcane using deep eutectic solvent pretreatment.

Sugarcane bagasse, a fundamental by-product of the sugar industry, was utilised to improve its digestibility for bioenergy applications. Choline chloride based deep eutectic solvents (DESs) were used for pretreatment of five different varieties of sugarcane bagasse (SRA1, SRA5, Q208, MA239, ISB) and a comparative study of compositional and morphological changes was performed. Three eutectic mixtures - choline chloride: malonic acid (1:1), choline chloride: glycerol (1:2) and choline chloride: lactic acid (1:5) were used to selectively remove lignin and improve saccharification efficiency. Physico-chemical characterizations performed using FE-SEM, FTIR, TGA and XRD analysis consistently indicated disruption of bagasse structure after DES pretreatment. Glucose recovery was predominantly influenced by the glucose content, as SRA1 variety showed the highest recovery of 92.8% for choline chloride: glycerol DES pretreatment. Choline chloride: lactic acid DES pretreatment demonstrated the most efficient lignin removal of 81.6% for ISB variety and the enzyme amenability was prominently increased to 98.5%.

Chourasia VR ，Pandey A ，Pant KK ，Henry RJ ... -  《-》

Synergism of sweeping frequency ultrasound and deep eutectic solvents pretreatment for fractionation of sugarcane bagasse and enhancing enzymatic hydrolysis.

Sugarcane bagasse (SCB) is an abundant agricultural waste in China and the conversion of the waste into plethora of useful resources is very vital. To achieve this, fractionation of the waste is highly important in the biomass biorefinery. The present study aims at investigating the synergistic role of deep eutectic solvents (DES) with sweeping frequency ultrasound (SFUS) and fixed frequency ultrasound (FFUS) in the fractionation of SCB to enhance the enzymatic saccharification process. Therefore, the effects of ultrasound (US) and DES conditions on the pretreatment efficiency were investigated. Under optimum SCB pretreatment conditions, FFUS (40 kHz, 60 min) + DES (choline chloride (ChCl)-lactic acid (LA), 120 °C, 3 h) and SFUS (40 kHz, 60 min) + DES (ChCl-LA, 120 °C, 3 h), the lignin removal rates were 80.13 and 85.62%, respectively. The hemicellulose removal rates were 78.08 and 90.46%, respectively; and the contents of glucose, xylose and arabinose in the liquid fractions after FFUS + DES pretreatment were 7.07, 17.95 and 3.01%, respectively. However, the yield of glucose, xylose, and cellobiose after enzymatic hydrolysis of the SFUS + DES pretreated SCB were 86.76, 38.68, and 20.76%. Analytical studies revealed that the SFUS + DES pretreatment can effectively destroy the ultrastructure of SCB and reduce the crystallinity of cellulose. Furthermore, the mechanism of pretreatment with SFUS + DES was proposed, which confirmed the excellent performance of SFUS + DES. Thus, the application of SFUS + DES pretreatment was able to improve the removal of lignin and hemicellulose from SCBs.

Ji Q ，Yu X ，Yagoub AEA ，Chen L ，Fakayode OA ，Zhou C ... -  《-》

Comprehensive understanding of enzymatic saccharification of Betaine:Lactic acid-pretreated sugarcane bagasse.

Green solvents, especially deep eutectic solvents (DESs), are widely applied to pretreat biomass for enhancing its enzymatic hydrolysis. In this work, lactic acid was selected as the hydrogen-bond-donor to prepare Betaine-base DES (Betaine:LA), The DES was utilized to pretreat sugarcane bagasse (SCB) at 160 ℃ for 80 min (severity factor LogR0 = 3.67). The influences of Betaine:LA treatment on the chemical composition, crystal and microstructure structure of cellulose, and cellulase digestion were investigated. The results showed that the lignin (47.1%) and xylan (44.6%) were removed, the cellulase digestibility of Betaine:LA-treated SCB was 4.2 times that of the raw material. This improved efficiency was attributed to the enhanced accessibility of cellulose, the weakened surface area of lignin, the declined hydrophobicity, and the decreased crystallinity of cellulose. Several compelling linear correlations were fitted between enzymatic hydrolysis and these alterations of physicochemical features, comprehensively understanding enzymatic saccharification of Betaine:LA-pretreated SCB.

Chen Y ，Ma C ，Tang W ，He YC ... -  《-》

Unveiling the potential of water as a co-solvent in microwave-assisted delignification of sugarcane bagasse using ternary deep eutectic solvents.

Deep eutectic solvents (DESs) have become popular owing to their biodegradability and recyclability. In this study, the influence of water as a co-solvent is demonstrated to enhance the properties of choline based ternary DESs. A fast and energy-efficient microwave-assisted pre-treatment process was developed for delignification of sugarcane bagasse (SB). The effectiveness of SB fractionation was revealed by incorporating Lewis acids (MgCl2.6H20, NiCl2.6H20) with the DESs for pre-treatment and Choline chloride: Ethylene glycol: NiCl2.6H20 (CC:EG:NI) at a molar ratio 1:2:0.016 with 20w% water as a co-solvent provided the most promising result, with 84% delignification and 99% enzyme digestibility. Water was also employed as an anti-solvent to facilitate lignin solubility and exhibited up to 26w% lignin yield from DES liquor with maximum DES recovery of 95% (w/w). Water distinctly affects the density, viscosity, and intermolecular hydrogen bonding of the DES and its impact on the process dynamics is worth further exploration.

Chourasia VR ，Bisht M ，Pant KK ，Henry RJ ... -  《-》