Removal of Bioactive Compound (γ-Oryzanol) from Rice Bran Oil-Based Biodiesel Using Deep Eutectic Solvent

Rice bran oil-based biodiesel contains high level of unsaponifiable matters (4.0 - 5.4 %) including bioactive compounds, such as γ-oryzanol, which have antioxidant activity. To fulfil the standard biodiesel specification, crude biodiesel should be refined. Isolation and purification of bioactive compounds from rice bran oil-based biodiesel are attractive options to further reduce the production cost of biodiesel since bioactive compounds can be sold separately at high price. The objective of this work is to study the effect of extraction time on the separation of fatty acid methyl ester (FAME) and -oryzanol from rice bran oil-based biodiesel using deep eutectic solvent (DES). Acid catalysed methanolysis was employed to convert rice bran oil into biodiesel at the following operation conditions: T = 60 °C, t = 8 h, molar ratio of oil to methanol = 1 : 10, and H2SO4 = 1 % of oil. Crude biodiesel obtained contains 89.05 % of FAME, 2.59 % of γ-oryzanol and less than 0.05 % of free fatty acids (FFA). The DES was prepared by mixing of choline chloride and ethylene glycol at a molar ratio of 1 : 2. The extraction temperature was varied at 30 °C, 45 °C and 60 oC. The extraction time was varied from 15 min to 240 min at constant temperature 30 °C and molar ratio crude biodiesel to DES 1/2 and 1/4. The highest FAME content (96.60 %) and the lowest γ-oryzanol (1.18 %) was obtained after extraction time of 240 min at 30 oC and molar ratio 1 : 4. This work shows that DES has a potential to purify biodiesel and reduce unsaponifiable matter (γ-oryzanol) from rice bran oil-based biodiesel.