Screening of impact factors on the enzymatic neutralization of Jatropha crude oil

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Abstract

Due to the high oil content of the seeds, Jatropha curcas L. became a focus of interest in the last decades. In order to prepare the oil for technical applications a refining is essential. This study is concerned with the enzymatic neutralization of aqueous-extracted Jatropha oil utilizing an immobilized lipase from Rhizomucor miehei. Free fatty acids were esterified with glycerol. Factors influencing the reaction were determined applying low acidic oil (acid number 4.2 mg KOH/g oil). Stirring rate of 300 rpm is adequate. The reaction rate was highest at 60°C. Free fatty acid content was reduced continuously with reaction time between 4 and 24 h. The variation of the free fatty acid content of Jatropha oil had only marginal influence on the reaction time. The amount of glycerol added to the reaction system was found to be optimal between 0.15 and 0.25 mol/L. Three percent w/w of immobilized lipase were enough to saturate the reaction system. A strong interaction between enzyme and glycerol content is likely and will be evaluated in an experimental design. The process designed after parameter screening yields acid numbers around 0.2 mg KOH/g oil. Remaining fatty acids are easily removed during the subsequent refining steps.

Practical applications: Enzymatic deacidification of Jatropha crude oil described in this study provides several advantages compared to the conventional alkaline process including lower oil losses, no wastewater generation and the avoidance of aggressive chemicals. On the basis of these benefits, an enzymatic approach holds potential to be applied industrially in the future since there is an increasing interest in more sustainable processes.

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