Enzymatic esterification of pre-treated and untreated acid oil soapstock

Abstract

The soapstock oil presents high Free Fatty Acid (FFA) content, being potentially a sustainable alternative feedstock for biodiesel production. In the present work, enzymatic esterification using a suspension of Thermomyces lanuginosus lipase was conducted on pre-treated and untreated acid oil from soapstock derived from the refining of vegetable oil mixtures. The enzyme suspension was prepared by mixing it with a 1 M phosphate buffer (1:10 V/V, enzyme:buffer). Esterification was conducted in an orbital shaking incubator at 40.0°C using a molar ratio of acid to methanol of 1:3, during 24 h at 200 rpm; monitoring was performed at 0, 7 and 24 h. Around 80% FFA reduction was obtained using raw and pre-treated oil, showing that the use of suspended enzyme avoids the need for pretreatment. Fatty Acid Methyl Ester content was determined, indicating that both esterification and transesterification reactions occurred. (c) 2018 Taylor & Francis Group, London, UK.