Integrated Bioethanol Production from Sugarcane Bagasse Using Betaine-PEG 400 Water Binary-Deep Eutectic Solvent: Enzymatic Hydrolysis, Fermentation, Inhibitor Profiling, and Techno-Economic Assessment

Abstract

This study presents integrated bioethanol production from sugarcane bagasse (SCB) using a water binary deep eutectic solvent (WB-DES) of betaine and polyethylene glycol 400 (PEG 400). Unlike prevailing acidic DES systems, this non d betaine–PEG 400 WB-DES enables selective lignin solubilization at mild temperatures while suppressing furan and acid-catalyzed degradation. The novelty lies in coupling WB-DES pretreatment with SHF and SSF bioconversion, inhibitor profiling, mass balance closure, and preliminary techno-economic assessment within one framework not previously reported for betaine–PEG 400 with SCB. Optimized pretreatment achieved 49.1 ± 1.8% delignification, 90.2 ± 2.1% cellulose recovery, higher crystallinity (59.8%), and a five-fold surface-area increase, improving enzymatic accessibility. Hydrolysis at 20 FPU/g yielded 82.3 ± 1.8% glucose (27.1 g/L). SHF produced 55.8 ± 1.6 g/L ethanol (83 ± 2.4% yield); SSF produced 51.5 ± 1.3 g/L (78 ± 2.0% yield) at higher productivity (0.54 g/L/h). Low inhibitor levels (furfural <0.12 g/L; HMF <0.06 g/L; acetic acid 0.9–1.3 g/L) eliminated detoxification. The process yielded ~158 mL ethanol per kg dry SCB, at an estimated minimum ethanol selling price of $0.42–0.48/L. This detoxification-free route provides a benchmarking dataset linking pretreatment chemistry, hydrolysis, fermentation, and economics for non-acidic WB-DES biorefineries.