Emmanuel Boures

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.

Lipase-catalyzed α-butylglucoside lactate synthesis in organic solvent for dermo-cosmetic application

Abstract α -Butylglucoside can be used as a vector for lactic acid: α -butylglucoside lactate synthesis can be achieved through transesterification catalyzed by immobilized Candida antarctica lipase. Synthesis was performed in an inert tertiary alcohol, 2-methyl-2-butanol. The reaction rapidly reached a thermodynamic equilibrium which could be shifted towards synthesis by alcohol product removal under reduced pressure: more than 95% of α -butylglucoside could be converted. However, the denaturating effect of lactate donor polar species affected lipase stability. A fed-batch process proved to be the most interesting method because it enables both high α -butylglucoside lactate concentrations to be obtained (∼150 g l −1 ) and lipase to be better protected from denaturation. Irritation tests on model skin and on butchered beef cornea finally showed the value of α -butylglucoside lactate as a lactic acid vector, offering the cosmetic benefits of the α -hydroxy acid but also eliminating the adverse effect of the free acid.

Enzymatic synthesis of AHA derivatives for cosmetic application

Abstract An immobilized lipase from Candida antarctica (Novozym 435) was used to catalyze synthesis of α-butylglucoside lactate by transesterification between α-butylglucoside and butyllactate in a solvent free medium. The influence of the reaction pressure on yield was investigated. The elimination of butanol co-product under reduced pressure resulted in the shift of the reaction equilibrium position in favor of synthesis. More than 95% of 0.5 M α-butylglucoside was converted in only 30 h. Consequently, very high α-butylglucoside lactate concentration (170 g/l) was obtained in a single batch reaction. Moreover, one purification step was enough to obtain α-butylglucoside lactate with a purity above 95% (w/w). Properties of α-butylglucoside lactate have been evaluated. This derivative is far less harmful than free lactic acid: a 0.55 M aqueous preparation is far less irritant than a lactic acid solution of a similar concentration.

Production, purification, and characterization of thermostable α-transglucosidase from Talaromyces duponti–application to α–alkylglucoside synthesis

Abstract The microorganism Talaromyces duponti ATCC 20805 can produce an extracellular glucosyltransferase (EC 2.4.1.24) with a high transglucosylating activity. A 100-h culture using maltodextrins as the carbon source gave an enzyme production of 11 U ml −1 . The enzyme was further purified to homogeneity by fractionation steps involving ammonium sulfate precipitation, hydrophobic interaction chromatography, ion-exchange chromatography, and chromatofocusing. The enzyme gave a single protein band on gel electrophoresis ( Mr = 170,000) but two protein bands on isoelectrofocusing (pI values 4.19 and 4.26). It is composed of two isoforms both showing transglucosylase activity. The two isoforms could be separated and their carbohydrate content evaluated. These were equal to 2.30 and 2.84% (w/w). The optimum pH and temperature for the enzymatic reaction are 4.5 and 70°C, respectively. The transglucosidase retained 50% activity after 73.2 h at 60°C. The high thermostability of the enzyme makes it particularly suitable for α-butylglucoside synthesis in biphasic medium by transfer of glucosyl moieties from maltooligosaccharide donors onto butanol.

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

The enzymatic synthesis of a mixture of unsaturated fatty acid α‐butylglucoside esters, containing more than 60% α‐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 α‐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 α‐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.