Combining the mechanical ball milling of the carbohydrate and the use of low solvent reaction media for the synthesis of fructose fatty acid esters by immobilized lipases

Abstract

Synthesis of carbohydrate fatty acid esters catalyzed by immobilized lipases is a pathway to obtain specific isomers from renewable feedstock, compared to unselective chemical esterification. While the use of low-solvent reaction media (≤ 10 %) offers advantages, the interactive effects of these media with biocatalysts and substrates should be modulated towards high catalytic efficiency and substrate availability. Among the investigated co-solvents, tert-butanol and DMSO in a mixture of lauric acid substrate/co-solvent (90/10; v/v) resulted in high bioconversion yields using either Novozym® 435 or Lipozyme® RM IM, as biocatalysts. Increased hydrophobicity of the Novozym® 435 immobilization support favored bioconversion, while polar substrate surface area enlargement by ball-milling improved productivity through enhancement of fructose availability. A compromise between bioconversion yield (19.7 %) and productivity (9.45 µmol/L min) was obtained in the reactions catalyzed by Novozym® 435 using ball-milled fructose at a concentration of 0.2 mol/L. Combining mechanical ball-milling of the substrates with low-solvent reaction media is expected to enhance and expand enzymatic synthesis of carbohydrate fatty acid esters.