22,23-Dihydroavermectin B1, ivermectin, derived from avermectin B1 by selective hydrogenation using Wilkinson's homogenous catalyst [Ph3P)3RhCl], was shown to be a highly effective drug for the treatment of a wide variety of metazoan parasitic diseases in animals.

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This study investigated high-solid loading deep eutectic solvent (DES) pretreatment for lignocellulose fractionation and subsequent conversion into platform chemicals (i.e., furfural, 2,3-butanediol). Switchgrass was pretreated with choline chloride:ethylene glycol (ChCl:EG) under acidic condition at high solid loadings of 20% and 27%. Cellulose was enriched to as high as 72.6% in pretreated switchgrass due to substantial removal of lignin and xylan but minor cellulose loss. Highly concentrated sugar hydrolysate containing up to 241.2 g/L fermentable sugars (206.5 g/L glucose and 34.7 g/L xylose) with 86.2% glucose yield was obtained from pretreated switchgrass via 25% solid loading enzymatic hydrolysis for only 48 h. The high sugar concentration allowed the production of 90.2 g/L 2,3-butanediol upon fermentation, a record high titer produced from lignocellulose hydrolysate without additional sugar concentration. ChCl:EG showed good recyclability, and its reuse facilitated lignin recovery from pretreatment liquor. The pretreatment liquor resulting from four pretreatment cycles was enriched with xylan-based sugars (96.8 g/L xylose equivalents), of which 84.6% was converted to furfural. 2D HSQC NMR revealed that β-O-4 interunit linkage experienced substantial cleavage during the pretreatment. The degree of bond cleavage depended on the solid loading for pretreatment. Lignin derived from a higher solid loading pretreatment preserved the original structure of natural lignin better, thus producing increased amounts of phenolic monomers upon pyrolysis. This study demonstrated that high-solid loading, ChCl:EG pretreatment was not only effective for biomass fractionation but also enabled industrially relevant production of concentrated sugar hydrolysate, furfural, and 2,3butanediol.

Biomass pretreatment enabling extraction of lignin with desirable properties (especially well-preserved β−O−4 linkages) while ensuring improved cellulose digestibility remains a challenge for sustainable biorefinery. This study aimed to address this challenge using a deep eutectic solvent (DES) comprising choline chloride and ethylene glycol (ChCl/EG) for switchgrass fractionation. Extensive characterization of extracted DES lignin was performed to understand how the lignin properties, including purity, molecular weight, thermal stability, and abundance of the β−O−4 linkages, were changed in the DESs under varied pretreatment conditions. Finely tuning the solvent system would steer DES-based biomass fractionation toward synchronizing the production of uncondensed lignin and digestible pulp. Appealing lignin properties, such as high-purity (91.4%), well-preserved β− O−4 linkages, and high volatility similar to that of cellulolytic enzyme lignin (CEL), is obtainable in this designer solvent system. At least 65% lignin can be removed, with the highest delignification reaching near 90% within 30 min. Overall, this versatile and tunable DES system is promising for lignocellulosic biomass processing and would fit into different biorefinery configurations toward valueadded valorization of lignocellulosic biomass.