Production of oleic acid ethyl ester catalyzed by crude rice bran (Oryza sativa) lipase in a modified fed-batch system: problem and its solution

Abstract

A fed-batch system was modified for the enzymatic production of Oleic Acid Ethyl Ester (OAEE) using rice bran (Oryza sativa) lipase by retaining the substrate molar ratio (ethanol/oleic acid) at 2.05: 1 during the reaction. It resulted in an increase in the ester conversion up to 76.8% in the first 6 h of the reaction, and then followed by a decrease from 76.8% to 22.9% in 6 h later. Meanwhile, the production of water in the reaction system also showed a similar trend to the trend of ester production. The water was hypothesized to lead lipase to reverse the reaction which resulted in a decrease in both (water and esters) in the last 6 h of the reaction. In order to overcome the problem, zeolite powders (25 and 50 mg/ml) were added into the reaction system at 5 h of the reaction. As the result, final ester conversions increased drastically up to 90 - 95.7% (1.17 – 1.24 times). The addition also proved a hypothesis that the water was involved in reducing the ester conversion in the last 6 h of the reaction. Thus, the combination was effective to produce the high final ester conversion.

Keywords

• Fed-batch system
• rice bran (Oryza sativa) lipase
• substrate molar ratio (ethanol/oleic acid)
• water
• zeolite powders