Process strategies for recovery of oil, sugars, and lipids from oilcane bagasse using natural deep eutectic solvents (NADES)

Authors: RAJ, TIRATH - University Of Illinois; Dien, Bruce; SINGH, VIJAY - University Of Illinois

Submitted to: Chemical Engineering Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2024
Publication Date: 5/29/2024
Citation: Raj, T., Dien, B.S., Singh, V. 2024. Process strategies for recovery of oil, sugars, and lipids from oilcane bagasse using natural deep eutectic solvents (NADES). Chemical Engineering Journal. https://doi.org/10.1016/j.cej.2024.152657.
DOI: https://doi.org/10.1016/j.cej.2024.152657

Interpretive Summary: There is a vast unmet need for production of low carbon intensity bioenergy crops that can be refined to bioethanol, biodiesel, and sustainable aviation fuel (SAF). Unfavorable economics has been a major barrier for commercial development. ARS researchers are working with collaborators to develop new high productivity bioenergy crops that are engineered to store oil in their stems. Economic analysis indicates that co-production of the valuable oil makes for a profitable venture. Oilcane is the name given to sugarcane plant engineered to produce oil and which are now being grown on experimental plots. This research demonstrates two technologies for processing the new crop that allow for collection of the cane sugar, plant oil, and “cellulosic” sugars. The most favorable process allowed for additional recovery of a third co-product called lignin, which had multiple potential market applications. The research is of immediate interest to the sugar mills located in Florida and Mississippi as well as the aviation industry in search of new ways to produce SAF.

Technical Abstract: Sugarcane is being enhanced as a bioenergy crop by engineering it to accumulate and store lipids along with polymeric sugars in vegetative tissues. However, there is no existing process that allows for processing this new crop to recover both oil and cellulosic sugars from the oilcane bagasse. Therefore, a comprehensive investigation of two pretreatment methods—natural deep eutectic solvents (NADES) and chemical-free hydrothermal pretreatment (HT) was conducted to judge their suitability for recovering fermentable sugars, lipids, and lignin from bagasse. Two NADEs, i.e., choline chloride: lactic acid (ChCl: LA) and betaine: lactic acid (BT: LA) were prepared using a 1:2 molar ratio and were evaluated for pretreatment of oilcane bagasse at 10, 20, and 50% (w/w) solids, followed by enzymatic hydrolysis at 10% (w/w) solids. Notably, ChCl: LA NADES treatment at 10%w/w solids at 140 °C for 2 h, solubilized 78.8% of lignin and 80.4% of hemicellulose and allowed 82.7% enzymatic conversion of glucans to glucose. In contrast, HT pretreatment removed approximately 87.6% of the hemicellulose and provided an enzymatic glucose yield of 69.7%. Furthermore, ChCl: LA operated at 50% solids loading enriched lipids 3-fold (9.2 wt.%) in recovered solids compared to HT (6.4%) and BT: LA (5.1%) pretreatment processes. NMR-HSQC analysis showed that ChCl: LA also cleaved the most lignin ß–O–4 linkages. This study demonstrates that NADES pretreatment is an effective method for recovering lipids, sugars, and lignin from bioenergy crops at high solid loading (50% w/w) within the context of an integrated biorefinery.