Sugarcane leaves: Pretreatment and ethanol fermentation by Saccharomyces cerevisiae

The susceptibility of sugarcane leaves to cellulase hydrolysis by GC220 cellulase (10 filter paper units (FPU)/gram dry weight basis (g, DS)) for 72 h was compared after pretreatment by autoclaving at 121 °C, 15 pounds per square inch (lb/in2) in the presence of either dilute sulfuric acid or lime. The optimal (from those evaluated) conditions for each type of pretreatment of green sugarcane leaves (20–40 mesh particle) at 6% weight by volume (w/v, DS), were found to be 1.5% (w/v) sulfuric acid and 2% (w/v) calcium hydroxide for 30 and 15 min, respectively. The acid pretreated samples released more glucose than the lime treated ones (5.7% and 3.9% weight by weight (w/w, DS), respectively). Accellerase™ 1000 hydrolysis (160 FPU/g, DS) of the dilute sulfuric acid pretreated ground sugarcane leaves suspended in 0.5 M citrate buffer, or in pretreatment hydrolysate yielded 0.104 and 0.163 g glucose/g (DS) of leaves after 6 h, respectively. Fermentation of the two above obtained glucose sources by Saccharomyces cerevisiae for 12 and 24 h, respectively, yielded ethanol at 4.8% and 8.0% (w/w, DS), respectively.