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Enzymatic Transesterification of Ethyl Ferulate with Fish Oil and Reaction Optimization by Response Surface Methodology

Zhiyong Yang1, Marianne Glasius2 and Xuebing Xu1*


1Department of Engineering, Aarhus University, Gustav Wieds Vej 10, DK-8000 Aarhus C, Denmark

2Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C, Denmark

Article history:

Received October 21, 2010
Accepted March 15, 2011

Key words:

transesterification, ethyl ferulate, fish oil, HPLC, HPLC-ESI-TOF-MS, feruloyl acylglycerol species, RSM

Summary:

The enzymatic transesterification of ethyl ferulate (EF) with fish oil from cod liver was investigated with Novozym® 435 as catalyst under solvent-free conditions. The purpose of the study is to evaluate the synthesis system for the production of feruloyl fish oil in industry. The modified HPLC method was first set up to characterise the reaction products together with liquid chromatography electrospray time-of-flight mass spectrometry (HPLC-ESI-TOF-MS). The influence of the addition of glycerol to the system on the feruloyl acylglycerol profile was investigated in terms of transesterification performance. The bioconversion rate of EF can be significantly increased with the increased formation of feruloyl fish oil products when appropriate amount of glycerol is present in the reaction. Therefore, an equivalent molar amount of glycerol was added to EF for the practical optimization of the system. The mutual effects of temperature (40 to 70 °C), reaction time (1 to 5 days), enzyme load (2 to 20 %) and molar ratio of fish oil and EF in the substrate (1 to 5) were thus studied with the assistance of response surface methodology (RSM) for the purpose of maximizing the formation of feruloyl fish oil. The models were well fitted and verified. The optimized conditions were found to be: temperature 70 °C, enzyme load 4.3 %, substrate ratio 4.7, and reaction time 5 days. Under these conditions, the maximum conversion of EF reached 92.4 %, and the formation of feruloyl fish oil reached 80.4 %, but the formation of by-product was minimized to 11.4 % only.


*Corresponding author:           xu@mb.au.dk
                                               ++45 8942 5089
                                               ++45 8612 3178

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