Bioconversion of Saccharum officinarum Leaves for Ethanol Production Using Separate Hydrolysis and Fermentation Processes

The leaves of sugarcane (Saccharum officinarum) are agricultural wastes that can be converted to bioethanol by separate hydrolysis and fermentation (SHF) processes. The effect of dilute acid hydrolysis conditions such as acid concentration, sugarcane leave concentration and hydrolysis time on sugar production were investigated. The optimized conditions were at 1%v/v of H2SO4, 100g/L of sugarcane leaves, and hydrolysis time 60min. The hydrolysate yielded sugar monomers at a concentration of 14.48g/L of xylose and 2.59g/L of glucose that was neutralized prior to fermentation. The fermentation process was carried out using shaken and unshaken stages. The shaken stage was maintained at 30 degrees C at 150rpm for 24h. It was found that Pichia stipitis BCC 15191 consumed only glucose then xylose after glucose depletion, while Candida shehatae TISTR 5843 used the both sugars concurrently in the exponential phase. Aggregation of P. stipitis BCC 15191 cells occurred during the stationary phase. Maximal ethanol yields of 0.21 and 0.20g (Ethanol)/g (Sugar consumptions) were obtained for C. shehatae TISTR 5843 and P. stipitis BCC 15191, respectively. This study demonstrates the potential value of this agricultural waste as a useful feedstock for biological generation of bioethanol.