Abstract:
Sugarcane leaves pretreated by dilute sulfuric acid was more susceptible to cellulase than those pretreated by lime. Optimal condition for the dilute sulfuric acid pretreatment was 6% (w/v) substrate (20-40 mesh particle size) loading, 1.5% (w/v) H2SO4 at 121oC, 15 lb/in2, 30 min. Hydrolysis of the dilute sulfuric acid pretreated sugarcane leaves slurry by cellulase (10 FPU/g, dry weigh basis (DS): β-glucosidase 3.55 salicin Unit/ml) for 6h yield 0.057 glucose g/g DS. Hydrolysis of the dilute sulfuric acid pretreated sugarcane leaves by AcellulaseTM1000 at 160 FPU/g (DS) (β-glucosidase 400 pNPGU/g) for 6 h resulted in glucose 9.8 g/l. The glucose was further fermented to ethanol by Saccharomyces cerevisiae TISTR 5596 for 24 h. Ethanol yield was 4.71 g/l (0.48 g/g glucose) or 0.20 g/g cellulose (0.08 g ethanol/g (DS) sugarcane leaves). Pretreatment of sugarcane leaves by dilute sulfuric acid released xylose 0.11 g/g (DS) which was the same as glucose released after cellulase hydrolysis (0.12 g/g (DS)). So, both of xylose and glucose were fermented to ethanol by Pichia stipitis and S.cerevisiae TISTR 5596, respectively. Flask scale fermentation gave ethanol from xylose (3.12 g/l or 0.35 g/g xylose) at 96h, and from glucose (2.9 g/l or 0.46 g/g glucose) at 12h. Total ethanol yield in flask scale was 6.02 g or 0.10 g ethanol/g (DS) sugarcane leaves. Three liters scale fermentation in 5L fermenter gave ethanol from xylose (4.08 g/l or 0.47 g/g xylose) at 96h, and from glucose (3.05 g/l or 0.49 g/g glucose) at 12h. Total ethanol yield in 3L fermenter scale was 7.13 g or 0.12 g ethanol/ g (DS) sugarcane leaves.
