Abstract
The lignocellulosic residue from the palm oil industry, oil palm empty fruit bunch (OPEFB), represents a challenge to both producing industries and environment due to its disposal difficulties. Alternatively, OPEFB can be used for the production of valuable products if pretreatment methods, which overcome OPEFB recalcitrance and allow tailored valorization of all its carbohydrates and lignin, are developed. Specifically, high-value applications for lignin, to increase its contribution to the feasibility of lignocellulosic biorefineries, demand high-purity fractions. In this study, acid-catalyzed organosolv using ethanol as a solvent was used for the recovery of high-purity lignin and digestible cellulose. Factors including catalyst type and its concentration, temperature, retention time, and solid-to-liquid (S/L) ratio were found to influence lignin purity and recovery. At the best conditions (0.07% H2SO4, 210 °C, 90 min, and S/L ratio of 1:10), a lignin purity and recovery of 70.6 ± 4.9% and 64.94 ± 1.09%, respectively, were obtained in addition to the glucan-rich fraction. The glucan-rich fraction showed 94.06 ± 4.71% digestibility within 18 h at an enzyme loading of 30 filter paper units (FPU) /g glucan. Therefore, ethanol organosolv can be used for fractionating OPEFB into three high-quality fractions (glucan, lignin, and hemicellulosic compounds) for further tailored biorefining using low acid concentrations. Especially, the use of ethanol opens the possibility for integration of 1st and 2nd generation ethanol benefiting from the separation of high-purity lignin.
Highlights
As a result of being one of the largest crude palm oil producers in the world, Indonesia produces around 37 million tons of oil palm empty fruit bunch (OPEFB) yearly [1]
OPEFB is mainly composed of cellulose, hemicellulose, and lignin that account to 24–65 wt%, 21–34 wt%, and 14–31 wt% of the material, respectively [5]
Derived sugars from the acid treatment of samples for compositional analysis and glucose released during enzymatic hydrolysis were measured using High Performance Liquid Chromatography (HPLC)
Summary
As a result of being one of the largest crude palm oil producers in the world, Indonesia produces around 37 million tons of oil palm empty fruit bunch (OPEFB) yearly [1]. Agronomy 2020, 10, 674 of OPEFB are crucial, and at a starting point, the existence of areas with higher production of palm oil can be used as an advantage for valorization by decreasing transportation costs [2]. OPEFB is mainly composed of cellulose, hemicellulose, and lignin that account to 24–65 wt%, 21–34 wt%, and 14–31 wt% of the material, respectively [5]. The holocellulosic (cellulose and hemicellulose) fragments can be enzymatically converted into simple sugars [6] for further conversion into value-added products. Enzymatic digestibility of lignocellulosic materials is limited by a number of factors such as the presence of lignin, cellulose crystallinity, degree of polymerization, acetyl groups bound to hemicellulose, surface area, and biomass particle size [7,8]
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