Title : Processing of advanced bioenergy crops using natural deep eutectic solvents (nadess) for sustainable biorefinery developments
Abstract:
Continuous exploitation of fossil resources and increasing energy consumption have urged the worldwide scientific community to look for a new alternative renewable feedstock for the production of bio-based materials, fuels, and chemicals. In view of this, a newly developed transgenic crop, i.e., oilcane, has been genetically engineered to accumulate vegetative lipids and carbohydrates in their plant tissues, thus can be considered as an alternative feedstock to cater for the enhanced biofuel yield by providing lipids along with cellulosic sugars for largescale biodiesel and bioethanol production. However, these components are entrapped in a highly recalcitrant lignin-carbohydrate matrix, which limits the efficient recovery of these components from transgenic crops for their downstream processing. Thus, natural deep eutectic solvents (NADES), a combination of hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA), have demonstrated exceptional solvent characteristics, an alternative to conventional organic solvents and benefited with easy preparation, low toxicity, high biodegradability, and high fractionation efficiency. NADES can act as adjuvants for weakening the lignin-carbohydrate recalcitrance matrix at the desired temperature of 100 to 160 °C and pretreatment circumstances while enhancing lignin solubilization. Thus, herein, we have synthesized several choline chloride-based NADES using bio-derived precursors, i.e., lactic acid, oxalic acid, glycerol, ethylene glycol, acetic acid by varying the molar ratio of HBD and HBA (1:1, 1:2) at 60 to 80 °C and were further employed for the pretreatment of oilcane bagasse for the fractionation of lipids and carbohydrates. Compositional analysis showed that oilcane bagasse is enriched with 3.3% of total lipids and 51% of carbohydrates. The initial study showed that the suitable eutectic combination of NADES, i.e., choline chloride and lactic acid in a 1:1 molar ratio at 60 to 80 °C, could effectively solubilize >80% lignin while enabling high biomass digestibility (>85%), and enhance lipid recovery (>80%). The research findings would further promote the design and fabrication of low-cost, environmentally friendly, biodegradable NADES-assisted pretreatment for enhanced lipid and sugar recovery from transgenic oilcane for renewable production under a circular biorefinery.
Keywords: Bioenergy crops, biofuels, fermentation, lignin, green solvents, eutectic solvents
