Bioethanol from pineapple peels using Saccharomyces cerevisiae through simultaneous saccharification and fermentation

In present study, pineapple (Ananas comosus) peel, being one of the most abundant agricultural wastes available in Malaysia and food processing by-products especially in pineapple canning factories, was used as the lignocellulosic feedstock for the production of bioethanol. Due to the natural recalcitrance of the lignocellulosic biomass, delignification by alkaline pretreatment was carried out prior to hydrolysis by acid pretreatment. During the experiment, two types of sequential alkaline-acid pretreatments, which are 2% sodium hydroxide (NaOH) pretreatment and 2% alkaline hydrogen peroxide (AHP) pretreatment, followed by 1% sulphuric acid (H2SO4) pretreatment were applied on the pineapple peels according to their optimized pretreatment conditions from other related studies. The solid portion of delignified hydrolysate was subjected to Simultaneous Saccharification and Fermentation (SSF) together with enzyme cellulase and inoculation of Saccharomyces cerevisiae. The fermentation processes were carried out under constant pH 4.5, for different fermentation temperatures (27, 37 and 40°C) and times (24, 48 and 72 hours) respectively. After distillation, the highest percentage of 16.11% (vlv) ethanol-water mixture can be obtained in NaOH pretreatment at 40°C, a better performance than the highest percentage of 10% (v/v) obtained in AHP pretreatment at 27°C. Based on the results of Fourier-Transform Infrared (FTIR) spectroscopic analysis, the presence of bioethanol can be detected in NaOH pretreated samples which were fermented at temperatures of 27°C and 40°C.