Subcritical Water-Carbon Dioxide Pretreatment of Oil Palm Mesocarp Fiber for Xylooligosaccharide and Glucose Production.

Norlailiza Ahmad,Mohd Rafein Zakaria,Mohd Ali Hassan,Hiroyuki Inoue,Hidayah Ariffin,Shinji Fujimoto,Yoshihoto Shirai,Mohd Zulkhairi Mohd Yusoff

doi:10.3390/molecules23061310

Abstract

The present work aimed to investigate the pretreatment of oil palm mesocarp fiber (OPMF) in subcritical H2O-CO2 at a temperature range from 150–200 °C and 20–180 min with CO2 pressure from 3–5 MPa. The pretreated solids and liquids from this process were separated by filtration and characterized. Xylooligosaccharides (XOs), sugar monomers, acids, furans and phenols in the pretreated liquids were analyzed by using HPLC. XOs with a degree of polymerization X2–X4 comprising xylobiose, xylotriose, xylotetraose were analyzed by using HPAEC-PAD. Enzymatic hydrolysis was performed on cellulose-rich pretreated solids to observe xylose and glucose production. An optimal condition for XOs production was achieved at 180 °C, 60 min, 3 MPa and the highest XOs obtained was 81.60 mg/g which corresponded to 36.59% of XOs yield from total xylan of OPMF. The highest xylose and glucose yields obtained from pretreated solids were 29.96% and 84.65%, respectively at cellulase loading of 10 FPU/g-substrate.

Highlights

Malaysia is the second largest oil palm producer, with more than 15 million tonnes of palm oil produced, along with the production of biomass such as oil palm empty fruit bunch (OPEFB), oil palm mesocarp fiber (OPMF) and oil palm frond fiber (OPFF) [1]
Due to the high demand and potential uses of XOs in the industry as well as abundant sources of OPMF from the oil palm industry, the present study aimed to evaluate the production of XOs and glucose from OPMF using subcritical H2 O-CO2 pretreatment under isothermal and non-isothermal conditions
Subcritical H2 O-CO2 pretreatment of OPMF was successfully performed under an optimal condition at CSPCO2 = −0.19 (180 ◦ C, 60 min, 3 MPa)

Summary

Introduction

Malaysia is the second largest oil palm producer, with more than 15 million tonnes of palm oil produced, along with the production of biomass such as oil palm empty fruit bunch (OPEFB), oil palm mesocarp fiber (OPMF) and oil palm frond fiber (OPFF) [1]. OPMF is one of the potential and attractive biomass which can be used as a biomaterial to produce many bio-products such as biosugar, biogas, biochar and biocomposite which can be further used by various industries. Due to the complex structure of OPMF, different pretreatments have been performed to disrupt the lignocellulose structure to give maximum access of enzymes to hemicellulose and cellulose [2,5]. Subcritical H2 O-CO2 pretreatment has become more attractive as it offers benefits such as the mild conditions used, less formation of undesirable by-products and the use of non-toxic gases [8]. Subcritical H2 O-CO2 pretreatment produces carbonic acid that facilitates the hydrolysis of hemicellulose in biomass with no negative impact on the environment since when the pressure is released, the gas will be neutralized [9,10]. It was reported that high-pressure CO2 penetrates the small pores in the biomass and helps in disrupting the biomass structure, improving the hydrolysis rate of hemicellulose in the biomass [8,11]

Methods

Results

Conclusion