Two-step pretreatment of oil palm trunk for ethanol production by thermotolerent Saccharomyces cerevisiae SC90.

Oil palm (Elaeis guineensis) trunk chips were processed by steam explosion under different steam conditions, followed by alkaline extraction and fermentation to produce efficient lignocellulosic ethanol as sustainable alternative energy resource. The optimum condition of steam explosion was attained at 210°C for 4 min (α-cellulose: 58.83% and lignin: 27.12%). Taguchi 3 factor design [(sodium hydroxide concentration (NaOH), temperature and time)] was performed to optimize alkaline extraction. The optimum condition at 15% NaOH, 90°C for 60 min gave highest percentage α-cellulose: 87.14% and lowest percentage of lignin: 6.13%. Simultaneous saccharification and fermentation (SSF) involved 10% dry weight pretreated fibers, Celluclast 1.5L (15 FPU /gram substrate), Novozyme 188 (15 IU/gram substrate) and Saccharomyces cerevisiae SC90. The highest ethanol concentration (C) produced during SSF was 44.25 g/L. Nonetheless, pre-hydrolysis simultaneous saccharification and fermentation gave 31.22 g/L (C). All results suggested that optimized two step pretreatment produced efficient ethanol.