Improved biodiesel production from sludge palm oil catalyzed by a low-cost liquid lipase under low-input process conditions

Sludge palm oil is a by-product produced as a result of oil loss into waste streams during the palm oil milling process. It is non-edible, inexpensive and abundantly available, thus making it an attractive feedstock for biodiesel production. However, it contains high contents of water and free fatty acids, rendering the conventional alkali-catalyzed process unsuitable. Therefore, this research aimed to improve the production of biodiesel from sludge palm oil using a low-cost liquid lipase (Eversa (R) Transform 2.0) produced from a genetically modified Aspergillus oryzae. The activity of the liquid lipase was determined to be 9600 IU mL(-1). We performed the reaction using low-input process conditions with only 0.2 wt% enzyme concentration and 5:1 methanol-to-oil molar ratio at a low operating temperature of 45 degrees C. Under an optimum stirring speed of 750 rpm, a crude biodiesel with a high ester content of approximately 94 wt% could be produced. Additionally, the crude glycerol produced has a higher purity compared to that produced via a chemical-catalyzed process. Overall, an economical and sustainable enzymatic process for the conversion of sludge palm oil into high quality biodiesel and glycerol has been demonstrated in this study. (C) 2021 Elsevier Ltd. All rights reserved.