A novel sequential ultrasound-rhamnolipid assisted [EMIM]OAc pretreatment for enhanced valorization of invasive Cogongrass to bioethanol

• Published in: Fuel (Guildford) Vol. 290; p. 119997
• Main Author: Goshadrou, Amir
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.04.2021; Elsevier BV
• Subjects: Accessibility; Acetic acid; Biofuels; Biomass; Biorefineries; Cellulose; Digestibility; Ethanol; Fermentation; Fungi; Impregnation; Invasive species; Ionic liquid; Ionic liquids; Ions; Irradiation; Lignin; Lignocellulose; Low-intensity sonication; Pretreatment; Radiation; Rhamnolipids; Saccharification; Simons’ stain; Sonication; Substrates; Synergistic effect; Ultrasonic imaging; Ultrasound; Accessibility; M. hiemalis; [EMIM]OAc; Ionic liquid; DO15; Lignocellulose; FTIR; FHY; TCSA; WRV; IHY; US; SS; IL; LOI; FESEM; (L/H)USx; Simons’ stain; ACSA; DB1; RL; TCI; Low-intensity sonication; NSSF; RLx
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2020.119997

[Display omitted] •First-ever report of a novel sequential US-RL assisted IL treatment of Cogongrass.•Synergistic pretreatment enhanced delignification and inhibited lignin deposition.•Semi-quantitative analyses revealed substantially expanded ACSA after pretreatment.•Biomass enzymatic digestibility was markedly improved (~19%) upon US-RL assistance.•Almost 1.6-fold improvement in ethanol yield was observed upon US-RL assistance. Cogongrass, one of the most invasive pest species worldwide, was considered as a promising bioresource for second-generation ethanol production. For the first time, it was successfully valorized to bioethanol using a novel sequential ionic liquid pretreatment assisted by synergistic effects of ultrasound irradiation and biosurfactant impregnation. The biomass was sonicated (50 and 100 W, 20 kHz) for 15 and 30 min, suspended in rhamnolipid solution (1, 2, and 3% w/w), and finally pretreated with 1-ethyl-3-methylimidazole acetate at 120 °C. Enzymatic digestibility of the regenerated biomass substantially enhanced by ~ 1.2-fold, upon a fast and low-intensity sonication (15 min, 50 W) followed by impregnation with the diluted rhamnolipid solution (2% w/w). Accordingly, non-isothermal simultaneous saccharification and fermentation of the pretreated Cogongrass by fungus M. hiemalis led to a maximum ethanol yield of ~ 195 (g/kg dry substrate), which was almost 1.6-fold higher than that obtained from the conventionally ionic liquid pretreated biomass. Comprehensive semi-quantitative analyses of the biomass together with FTIR and FESEM measurements revealed major improvements in surface area, surface hydrophilicity, pore sizes and volumes, cellulose crystallinity, and morphological features following the pretreatment. The findings may also provide a promising approach for enhanced recycling of the expensive ionic liquid and lignin in a biorefinery framework; however, more investigation should be dedicated to this subject.