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Production of Bio-Ethanol by Integrating Microwave-Assisted Dilute Sulfuric Acid Pretreated Sugarcane Bagasse Slurry with Molasses

Yu, Na, Tan, Li, Sun, Zhao-Yong, Tang, Yue-Qin, Kida, Kenji
Applied biochemistry and biotechnology 2018 v.185 no.1 pp. 191-206
bioethanol, biomass, ethanol, ethanol production, feedstocks, fermentation, hydrolysis, microwave treatment, molasses, saccharification, slurries, sugarcane bagasse, sugars, sulfuric acid, toxic substances
Sugarcane bagasse (SCB) and molasses, known as carbohydrate-rich biomass derived from sugar production, can serve as feedstock for bio-ethanol production. To establish a simple process, the production of bio-ethanol through integration of whole pretreated slurry (WPS) of SCB with molasses was investigated. The results showed that microwave-assisted dilute sulfuric acid pretreatment reduced the formation of toxic compounds compared to a pretreatment process involving “conventional heating”. Pretreatment at 180 ᵒC with 10% w v⁻¹ solid loading and 0.5% w v⁻¹ H₂SO₄ was sufficient to achieve efficient enzymatic saccharification of WPS. By conducting separate hydrolysis and fermentation (SHF), an ethanol yield of 90.12% was obtained from the mixture of WPS and molasses, but the ethanol concentration of 33.48 g L⁻¹ was relatively low. By adopting fed-batch SHF, the ethanol concentration reached 41.49 g L⁻¹. Assuming that the molasses were converted to ethanol at an efficiency of 87.21% (i.e., ethanol was obtained from fermentation of molasses alone), the ethanol yield from WPS when a mixture of WPS and molasses was fermented was 78.30%, which was higher than that of enzymatic saccharification of WPS (73.53%). These findings suggest that the production of bio-ethanol via integration of WPS with molasses is a superior method. Graphical Abstract ᅟ