Production of glucose from mixed oil palm biomass using hydrothermal pretreatment

As the world second biggest palm oil producer, Malaysia has most of its agricultural land planted with oil palm (Elaeis guineensis Jacq.). In conjunction with that, various and bulky amount of oil palm biomass were produced from the plantations and mills which contained a high amount of lignocellulosic components. The conversion of oil palm biomass into a value added product such as glucose helps to reduce the abundance of oil palm biomass. However, the structure of the biomass is compact and tough to be broken down. Therefore, pretreatment process is required to open up the lignocellulosic structure for enzymatic reaction thus improving the production of glucose. Hydrothermal pretreatment process is an effective and environmental-friendly process for biomass fractionation due to its ability to solubilize hemicellulose; open the lignocellulosic structure and contributes to self-association of water molecules to create hydronium ions that can turn water pH into acidic, thus increasing the efficiency of pretreatment. Previous studies were using individual biomass in various pretreatment processes had shown a great effect on glucose conversion. In this study, hydrothermal pretreatment process was tested on mixed oil palm biomass to accommodate the huge amount of biomass produced daily. The aims of this experiment are to determine the effectiveness of hydrothermal pretreatment towards the lignocellulosic composition of mixed oil palm biomass and also to improve the glucose yield from pretreated mixed oil palm biomass using Acremonium cellulase. Different weight ratios of oil palm biomass mixture were treated, i.e. 1:1:1, 1:1:2, 1:2:1 and 2:1:1 of oil palm frond fiber: oil palm empty fruit bunch: oil palm mesocarp fiber (OPFF:OPEFB:OPMF), respectively. The individual and mixed biomass were then subjected to hydrothermal pretreatment with different severity factors (log R0) of 3.37 – 3.96 using miniclave reactor. The individual samples were represented as a control to investigate the effectiveness of mixed samples. The morphological structure was examined with scanning electron microscope, wide-angle x-ray diffraction, Fourier-transform infrared spectral analysis and Brunauer-Emmett-Teller surface area analyses to observe the structure of oil palm biomass before and after pretreatment. The compositional analysis results were obtained by following National Renewable Energy Laboratory (NREL) method using dilute acid hydrolysis. Enzymatic hydrolysis of untreated and treated individual and mixed oil palm biomass was performed using 10 FPU of Acremonium cellulase per g of biomass was studied. The enzymatic hydrolysis was conducted at 50˚C for 72 hours in shaking condition. Acremonium cellulase has endocellulase and β-glucosidase activities which converted cellulose into monosaccharides mainly glucose. In conclusion, the hydrothermal pretreatment had shown positive feedback towards high cellulose amount (53.8 ± 0.4%) of 1:2:1 mixed ratio under 190˚C for 10 min. The highest glucose yield also produced from the same mixed ratio under the same condition at 99.0 ± 0.8% under oil palm biomass ratio of 1:2:1 (OPFF:OPEFB:OPMF). Besides, the mixed sample also showed an increment of 22% of glucose conversion increment compared to the individual sample