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Keywords:

  • 1,3-DAG;
  • Esterification;
  • Lecitase® Ultra;
  • Reaction conditions;
  • Solvent-free system

Abstract

Lecitase® Ultra, a phospholipase, was explored as an effective biocatalyst for direct esterification of glycerol with oleic acid to produce 1,3-DAG. Experiments were carried out in batch mode, and optimal reaction conditions were evaluated. In comparison with several organic solvent mediums, the solvent-free system was found to be more beneficial for this esterification reaction, which was further studied to investigate the reaction conditions including oleic acid/glycerol mole ratio, temperature, initial water content, enzyme load, and operating time. The results showed that Lecitase® Ultra catalyzed a fast synthesis of 1,3-DAG by direct esterification in a solvent-free medium. Under the optimal reaction conditions, a short reaction time 1.5 h was found to achieve the fatty acid esterification efficiency of 80.3 ± 1.2% and 1,3-DAG content of 54.8 ± 1.6 wt% (lipid layer of reaction mixture mass). The reusability of Lecitase® Ultra was evaluated via recycling the excess glycerol layer in the reaction system. DAG in the upper lipid layer of reaction mixture was purified by molecular distillation and the 1,3-DAG-enriched oil with a purity of about 75 wt% was obtained.

Practical applications: The new Lecitase® Ultra catalyzed process for production of 1,3-DAG from glycerol and oleic acid described in this study provides several advantages over conventional methods including short reaction time, the absence of a solvents and a high product yield.