Biocatalytic Synthesis of Polyglycerol Polyricinoleate: A Comparison of Different Commercial Lipases

S. Ortega, J. L. Gómez, J. Bastida, M. F. Máximo, M. C. Montiel and M. Gómez

Abstract
This paper describes the studies carried out to select the most suitable lipase as catalyst for the esterification of polyglycerol with polyricinoleic acid to yield polyglicerol polyricinoleate (PGPR), a value-added, bio-based food emulsifier. The enzymes assayed were lipases from Rhizopus arrhizus, Rhizopus oryzae and Mucor javanicus, previously selected because of their suitable activity and moderate cost. First, the reaction was catalyzed by free lipases in a batch reactor and the influence of different operating conditions (initial water content, amount of enzyme and temperature) on the progress of the reaction was studied. Next, the three lipases were immobilized by physical adsorption on the anion exchange resin, Lewatit MonoPlus MP 64, providing derivatives with a high activity and stability. Recovery of the immobilized derivative from the reaction medium was conducted with very good yields (≥ 99 %) and no loss of activity of the derivative with successive uses was proved. Finally, a high performance reactor, operating at low pressure and a dry atmosphere, was used to synthesise PGPR using the immobilized enzymes. Both Rhizopus arrhizus and Rhizopus oryzae lipases allowed the production of a PGPR which fulfils the “specific purity criteria on food additives other than colours and sweeteners” established by the Commission of the European Communities (AV ≤ 6 mg KOH/g), with an acid value of 4.91 and 5.31 mg KOH/g respectively.

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Keywords
Polyglycerol polyricinoleate, lipase, immobilized enzymes, heterogeneous reaction, enzyme biocatalysis, vacuum reactor