Elucidating multi-scale deconstruction of bamboo crystalline cellulose by novel acetylcholine chloride based deep eutectic solvents for enhanced enzymatic hydrolysis

Exploration and application of novel and sustainable deep eutectic solvents (DESs) on lignocellulose pretreatment are promising approaches to efficient bioconversion. However, comprehensive understanding on efficient DESs selection and inner mechanisms of lignocellulose deconstruction are still limited. Herein, bio-based acetylcholine chloride (AChCl) was firstly utilized as hydrogen bond acceptor in cooperation with lactic acid, urea and glycerol respectively for microwave-assisted pretreatment on moso bamboo in short time. High enzymatic conversion yield of bamboo cellulose (-85%) was achieved by lactic acid-AChCl DES due to its lower pH value and viscosity, followed by glycerol-AChCl and urea-AChCl DES. In addition to the features of proposed DESs, changed chemical and physical properties of highly recalcitrant bamboo biomass after pretreatments were systematically determined. Besides of great amount of lignin (-90%)/ xylan (100%) removal, micro- to nanoscale variations of cellulose structures including more dissociated microfibrils, lowered crystallinity, and enlarged crystallite sizes all played key roles in promoting bioconversion yields. Moreover, the multi-factors contributing to improved hydrolysis performance were integrated to evaluate the effects of novel DESs pretreatments on lignocellulose deconstruction, which may provide new strategies on bioconversion enhancement and process optimization.

Automated summary

Exploring and applying novel and sustainable deep eutectic solvents (DESs) for lignocellulose pretreatment is a promising approach for efficient bioconversion. However, the selection of efficient DESs and the inner mechanisms of lignocellulose deconstruction are still limited. In this study, bio-based acetylcholine chloride (AChCl) was used as a hydrogen bond acceptor with lactic acid, urea, and glycerol for microwave-assisted pretreatment of moso bamboo. The lactic acid-AChCl DES showed the highest enzymatic conversion yield of bamboo cellulose (-85%) due to its lower pH value and viscosity, followed by glycerol-AChCl and urea-AChCl DES. The chemical and physical properties of bamboo biomass after pretreatment were systematically determined, and it was found that the removal of lignin (-90%)/xylan (100%) and changes in cellulose structures played key roles in promoting bioconversion yields. The effects of novel DESs pretreatments on lignocellulose deconstruction were evaluated, which may provide new strategies for bioconversion enhancement and process optimization.