Enzymatic synthesis of alpha-butylglucoside linoleate in a packed bed reactor for future pilot scale-up

The enzymatic synthesis of a mixture of unsaturated fatty acid alpha-butylg lucoside esters, containing more than 60% alpha-butylglucoside linoleate, w as achieved through lipasecatalyzed esterification. The continuous evaporat ion under reduced pressure of the water produced enabled substrate conversi ons greater than 95% to be reached. Two immobilized lipases from Candida an tarctica (Chirazyme L2, c.-f., C2) and Rhizomucor miehei (Chirazyme L9, c.- f.) were compared in stirred batch and packed bed configurations. When the synthesis was carried out in stirred batch mode, C. antarctica lipase appea red to be of greater interest than the R. miehei enzyme in terms of stabili ty and regioselectivity. Surprisingly, a change in the process design to a packed bed configuration enabled the stability of R. miehei lipase to be si gnificantly improved, while the C. antarctica lipase efficiency to synthesi ze unsaturated fatty acid alpha-butylglucoside esters was slightly decrease d. Water content in the microenvironment of the biocatalyst was assumed to be responsible for such changes. When the process is run in stirred batch m ode, the conditions used promote the evaporation of the essential water sur rounding the enzyme, which probably leads to R. miehei lipase dehydration. In contrast, the packed bed design enabled such water evaporation in the mi croenvironment of the biocatalyt to be avoided, which resulted in a tremend ous improvement of R. miehei lipase stability. However, C. antarctica lipas e led to the formation of 3% diesters, whereas the final percentage of dies ters reached 21% when R. miehei enzyme was used as biocatalyst. A low conte nt of diesters is of greater interest in terms of alpha-butylglucoside lino leate application as linoleic acid carrier, and therefore the enzyme choice will have to be made depending on the properties expected for the final pr oduct.