Optimization of NaOH-catalyzed steam pretreatment of empty fruit bunch

Abstract

BackgroundEmpty fruit bunch (EFB) has many advantages, including its abundance, the fact that it does not require collection, and its year-round availability as a feedstock for bioethanol production. But before the significant costs incurred in ethanol production from lignocellulosic biomass can be reduced, an efficient sugar fractionation technology has to be developed. To that end, in the present study, an NaOH-catalyzed steam pretreatment process was applied in order to produce ethanol from EFB more efficiently.ResultsThe EFB pretreatment conditions were optimized by application of certain pretreatment variables such as, the NaOH concentrations in the soaking step and, in the steam step, the temperature and time. The optimal conditions were determined by response surface methodology (RSM) to be 3% NaOH for soaking and 160°C, 11 min 20 sec for steam pretreatment. Under these conditions, the overall glucan recovery and enzymatic digestibility were both high: the glucan and xylan yields were 93% and 78%, respectively, and the enzymatic digestibility was 88.8% for 72 h using 40 FPU/g glucan. After simultaneous saccharification and fermentation (SSF), the maximum ethanol yield and concentration were 0.88 and 29.4 g/l respectively.ConclusionsDelignification (>85%) of EFB was an important factor in enzymatic hydrolysis using CTec2. NaOH-catalyzed steam pretreatment, which can remove lignin efficiently and requires only a short reaction time, was proven to be an effective pretreatment technology for EFB. The ethanol yield obtained by SSF, the key parameter determining the economics of ethanol, was 18% (w/w), equivalent to 88% of the theoretical maximum yield, which is a better result than have been reported in the relevant previous studies.

Sodium Hydroxide-Steam Explosion Treated Oil Palm Empty Fruit Bunch: Ethanol Production and Co-Fermentation with Cane Molasses

“…Likewise, steam treatment at 180 C or above removes silica bodies from the OPEFB structure, increasing enzyme accessibility to the internal layers of OPEFB (Bahrin et al 2012). A combination of NaOH and steam pretreatment has an even greater effect (Ariffin et al 2008); lignin is effectively removed from OPEFB treated with NaOH and steam at 160 °C (Choi et al 2013). Subsequent fermentation to ethanol of the pretreated OPEFB by the simultaneous saccharification and fermentation (SSF) process yields ethanol at 29.4 g/L or 0.18 g/g OPEFB.…”

“…The reducing sugar liberated by cellulase hydrolysis was highest when the OPEFB was soaked in 2 M NaOH (Fig. 2), which reflects that the removal of lignin from the OPEFB fibers increased with higher concentrations of NaOH (Choi et al 2013). Thus, pretreatment with 2 M NaOH was used for subsequent experiments.…”

“…Lignin encases cellulose and hemicellulose in a structure that protects them from enzyme digestion (Ariffin et al 2008). The lignin content of a lignocellulosic biomass has the highest impact on its enzymatic digestion, as lignin reduces enzyme efficiency (Choi et al 2013).…”

Production of Xylitol from Oil Palm Empty Friuts Bunch: A Case Study on Bioefinery Concept

“…Physicochemical process is a combination of both involving the addition of chemical substances and extreme physical process, such as steam explosion. Different pretreatment process has been evaluated in utilizing EFB for bioethanol production, for example the research studied the dilute alkaline steam explosion (Choi et al, 2013), other research studied the combine use of white rot fungi and phosphoric acid (Isroi et al, 2012), and the use of bisulphite for EFB pretreatment (Tan et al, 2012). It should be noted that the main compound needed for xylitol production, the hemicellulose, is easier to degrade than cellulose or lignin.…”

Partial Simultaneous Saccharification and Fermentation at High Solids Loadings of Alkaline-pretreated Miscanthus for Bioethanol Production

“…However, this explosion was necessary to easily collect the samples from the reactor due to its structural limitation through the cyclone system. Choi et al (2013) optimized NaOH-catalyzed explosion pretreatment using response surface methodology (RSM) with the following conditions: 3% NaOH, 160 °C, and 11.3 min. The pressurized nitrogen gas was 20 bars , while that of the nitrogen in this study was 10 bars.…”