Structural Changes of Oil Palm Empty Fruit Bunch (OPEFB) after Fungal and Phosphoric Acid Pretreatment

Abstract

Oil palm empty fruit bunch (OPEFB) was pretreated using white-rot fungus Pleurotus floridanus, phosphoric acid or their combination, and the results were evaluated based on the biomass components, and its structural and morphological changes. The carbohydrate losses after fungal, phosphoric acid, and fungal followed by phosphoric acid pretreatments were 7.89%, 35.65%, and 33.77%, respectively. The pretreatments changed the hydrogen bonds of cellulose and linkages between lignin and carbohydrate, which is associated with crystallinity of cellulose of OPEFB. Lateral Order Index (LOI) of OPEFB with no pretreatment, with fungal, phosphoric acid, and fungal followed by phosphoric acid pretreatments were 2.77, 1.42, 0.67, and 0.60, respectively. Phosphoric acid pretreatment showed morphological changes of OPEFB, indicated by the damage of fibre structure into smaller particle size. The fungal-, phosphoric acid-, and fungal followed by phosphoric acid pretreatments have improved the digestibility of OPEFB’s cellulose by 4, 6.3, and 7.4 folds, respectively.

Disruption of Oil Palm Empty Fruit Bunches by Microwave-assisted Oxalic Acid Pretreatment

“…In this study, the peaks at 1423 cm -1 and 902 cm -1 were more pronounced with increasing temperature, even though the LOI values of the untreated and the treated OPEFB were not different (Table 3). Structural changes in lignin and loss of aromatic units due to chemical bond disruption effects of the MAOxAc pretreatment can be observed by the increasing intensity in signals related to the lignin structure (1633, 1600, 1506, 1456 and 1255 cm -1 ) [27,31,33,34]. In the spectrum of the untreated OPEFB (Figure 4), the aforementioned peaks could be observed, even though they did not appear clearly.…”

“…These results show that the cellulose content in the OPEFB residue was increased, while the hemicellulose content was decreased. This is similar to the change in structure of sugarcane bagasse after dilute sulfuric acid pretreatment with microwave heating and the structure of OPEFB after fungal pretreatment followed by phosphoric acid pretreatment [23,31]. Nelson & Connor [32] proposed a crystallinity index called LOI, which is obtained by calculating the ratio between the absorption bands at 1429 and 893 cm -1 .…”

Characterization of Hemicelluloses From Oil Palm Empty Fruit Bunches Obtained by Alkaline Extraction and Ethanol Precipitation

“…The decrease in intensity at wavenumber 1165 cm -1 was greater than that at wavenumber 1277 cm -1 after alkaline extraction. This suggests that syringyl was more solubilized by alkaline extraction than guaicyllignin [22]. Band at ̴ 1035 cm -1 is responsible for typical of xylan-rich polysaccharides which indicated a dominant xylan of the hemicellulosic fractions [23].…”

Effect of cooking temperature on the crystallinity of acid hydrolysed-oil palm cellulose

“…Peaks at 1427 cm -1 and 1315 cm -1 was detected in all spectra relatively refered to intermolecular hydrogen at the C 6 and OH in-plane bending vibration respectively [12,16]. Peak at 895 cm -1 was assigned to the β-glycosidic linkage while peak around 1032-1022 cm -1 was assigned to C-O stretch of cellulose [25]. All functional groups encountered in cellulose molecule were present as expected.…”