Enzymatic hydrolysis of soybean and waste cooking oils under ultrasound system

• Enzymatic hydrolysis of soybean and waste cooking oils in ultrasound system.
• Ultrasound increased the initial reaction with no damage to protein structure.
• FFA contents of about 60 wt% was obtained from soybean and waste cooking oils.
• Lipase could be reused over several cycles.
• Environmentally benign technique with great potential for large scale purposes.

This work reports the enzymatic hydrolysis of soybean and waste cooking oils in ultrasound system towards producing free fatty acids hence allowing faster esters production. For this purpose, the following experimental conditions were investigated: temperature (40–60 °C), molar ratio of oil to water (1:9; 1:10; 1:20, 1:40 and 1:46), enzyme (Lipozyme TL IM) concentration (1–10 wt%, based on the total mass of substrates), keeping the reaction time fixed at 2 h, 300 rpm stirring rate and ultrasonic output power of 132 W. Results showed a content of 60 wt% FFA for soybean oil while 61 wt% was reached for waste cooking oil. After the experimental design, a kinetic study was performed at the best temperature, molar ratio (oil:water), enzyme concentration varying reaction times (until 24 h) with and without ultrasound. The use of ultrasound showed to be effective, increasing the initial reaction, providing very satisfactory reaction yields at short reaction times with no damage to protein structure thus allowing enzyme reuse.

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