Vacuum-assisted Black Liquor-recycling Enhances The Sugar Yield Of Sugarcane Bagasse And Decreases Water And Alkali Consumption

Amongst the various pretreatment methods,alkalic pretreatment has many advantages,including low temperatures and pressure,which significantly improves the enzymatic hydrolysis effect.However,black liquor(BL)remains a critical problem during alkalic pretreatment.To solve this issue,a novel pretreatment strategy termed vacuum-assisted black liquor-recycling pretreatment(VABLR),was established to pretreat sugarcane bagasse(SCB).Firstly,SCB was pretreated with 2% Na OH at 121°C for 1 h under vacuum condition.The produced BL was used for subsequent pretreatments after p H recovery with Na OH.The pretreated SCBs were subject to enzymatic hydrolysis and separate hydrolyzation and fermentation(SHF)without washing to neutral p H.BL was recycled for seven times.The results indicated that glucose yields did not significantly differ between pretreatment with Na OH and recovered BL.The enzymatic hydrolysis and the fermentation resulted in maximum 0.35 g/g of glucose yield and 116.5 g/Kg of ethanol yield respectively.Compared with conventional pretreatment with Na OH,the VABLR method showed high conversion rates of cellulose into monosaccharaides,whilst preserving ?20% and ?46% of alkali and water usage,respectively.Finally,the physicochemical characteristics of the pretreated SCB residues were analyzed by scanning electron microscopy(SEM),Fourier-transform infrared spectroscopy(FT-IR)and thermogravimetric analysis(TGA).These results suggested that some hemicellulose and lignin was removed during the pretreatment process.By recovering the p H,pretreatment using recycled BL could achieve similar effects to fresh Na OH solution.The overall results indicate that BL-recycling has economic benefit for SCB pretreatment and bioethanol production.