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-butylglucoside esters, containing more than 60% alpha-butylglucoside linoleate, was achieved through lipase-catalyzed esterification. The continuous evaporation under reduced pressure of the water produced enabled substrate conversions greater than 95% to be reached. Two immobilized lipases from Candida antarctica (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 appeared to be of greater interest than the R. miehei enzyme in terms of stability and regioselectivity. Surprisingly, a change in the process design to a packed bed configuration enabled the stability of R. miehei lipase to be significantly improved, while the C. antarctica lipase efficiency to synthesize unsaturated fatty acid alpha-butylglucoside esters was slightly decreased. Water content in the microenvironment of the biocatalyst was assumed to be responsible for such changes. When the process is run in stirred batch mode, the conditions used promote the evaporation of the essential water surrounding the enzyme, which probably leads to R. miehei lipase dehydration. In contrast, the packed bed design enabled such water evaporation in the microenvironment of the biocatalyt to be avoided, which resulted in a tremendous improvement of R. miehei lipase stability. However, C. antarctica lipase led to the formation of 3% diesters, whereas the final percentage of diesters reached 21% when R. miehei enzyme was used as biocatalyst. A low content of diesters is of greater interest in terms of alpha-butylglucoside linoleate application as linoleic acid carrier, and therefore the enzyme choice will have to be made depending on the properties expected for the final product.

Enzymatic synthesis of unsaturated fatty acid glucoside esters for dermo-cosmetic applications.

Unsaturated fatty acid alpha-butylglucoside esters were prepared by enzymatic esterification of alpha-butylglucoside in nonaqueous media. Conditions were firstly optimized using oleic acid as acyl group. Synthesis was possible in several solvents but the presence of water co-product in the medium limited the reaction to a thermodynamic equilibrium corresponding to a maximal conversion yield of 62%. In pure molten substrates, the removal of water under reduced pressure enabled yields superior to 95% to be obtained. Product profiles depended on enzyme origin : whatever the support, immobilized lipase B from Candida antarctica proved to be far more regioselective for the primary hydroxyl group of glucose than immobilized lipase from Rhizomucor miehei. Results obtained could be easily transposed to the acylation of alpha-butylglucoside with a commercial mixture of unsaturated fatty acids containing more than 60% of linoleic acid. The biocatalyst could be recycled more than ten times without any significant activity loss.

Enzymatic synthesis of alpha-butylglucoside lactate: a new alpha-hydroxy acid derivative.

An alpha-hydroxy acid derivative, alpha-butylglucoside lactate, was successfully prepared by enzymatic transesterification of alpha-butylglucoside with a lactate alkyl ester in a non-aqueous medium using immobilized lipase as biocatalyst. Ester synthesis in organic solvent was optimized. Solvent choice was made on the basis of substrate solubility and enzyme stability in the medium. A solvent-free reaction using butyllactate as lactate donor led to the highest yields. In the presence of 0.5M alphabutylglucoside and 100 g/L Novozym(R), a 67 % yield could be obtained within 40 h at 50 degrees C. However, the presence of butanol by-product limited the reaction to a maximum that could not be exceeded in closed systems. The elimination of the alcohol under reduced pressure resulted in the complete equilibrium shift of the transesterification reaction in favor of synthesis; below 15 mbars, more than 95% of 0.5M alpha-butylglucoside could be converted within 30 h. Moreover, simultaneous evaporation of water allowed hydrolysis of butyllactate to be eliminated. Consequently, a very high alpha-butylglucoside lactate concentration (170 g/) could be obtained in a single batch reaction. A single purification procedure, consisting of butyllactate extraction with hexane, enabled the product to be obtained at a purity above 95% (w/w). 1H and 13C NMR analysis later demonstrated that lactic acid was exclusively grafted onto the primary hydroxyl group of alphabutylglucoside.