Enzymatic in situ saccharification of sugarcane bagasse pretreated with low loading of alkalic salts Na2SO3/Na3PO4 by autoclaving

- Combined Na2SO3/Na3PO4 with hot water in “one-pot” was firstly used to pretreat SCB.
- Dilute alkalic salt (0.4% Na3PO4, 0.03% Na2SO3) was chosen as pretreatment media.
- The optimum pretreatment temperature and time were 110 °C and 40 min, respectively.
- Saccharifications of 20-50 g/L SCB were obtained at 64.9-72.8% in alkalic salt media.
- Ethanol fermentability of SCB-hydrolysates was demonstrated in alkalic salt media.

Sugarcane bagasse (SCB) is an abundant, renewable and inexpensive agricultural byproduct for the production of biofuel and other biobased products. To effectively saccharify SCB with cellulases, combination with dilute alkali salts Na2SO3/Na3PO4 (0.4% Na3PO4, 0.03% Na2SO3) at 7.5% sulfidity and hot water (DASHW) in “one-pot” pretreatment media by autoclaving at 110 °C for 40 min was attempted to pretreat SCB in this study. Furthermore, FT-IR, XRD and SEM were employed to characterize the changes in the cellulose structural characteristics (porosity, morphology, and crystallinity) of the pretreated Na2SO3/Na3PO4-SCB solid residue, which indicated that combination pretreatment could effectively remove lignin and hemicellulose for enhancing enzymatic saccharification. After 72 h, the reducing sugars and glucose from the enzymatic in situ hydrolysis of 50 g/L Na2SO3/Na3PO4-SCB in dilute Na2SO3/Na3PO4 (0.27% Na3PO4, 0.02% Na2SO3) media were obtained at 33.8 and 21.8 g/L, respectively. Finally, the SCB-hydrolysates containing 20 g/L glucose were used for ethanol fermentation in the presence of dilute alkali salts. After 48 h, the ethanol yield was 0.42 g ethanol/g glucose, which represents 82.1% of the theoretical yield. In conclusion, this study provided an effective pretreatment strategy for enhancing SCB's saccharification, which has potential application of other lignocellulosic materials.