Enzymatic synthesis of fatty acid esters of di-and trisaccharides is limited by the fact that most biological catalysts are inactivated by the polar solvents (e.g. dimethylsulfoxide, dimethylformamide) where these carbohydrates are soluble. This article reviews the methodologies developed to overcome this limitation, namely those involving control over the reaction medium, the enzyme and the support. We have proposed the use of mixtures of miscible solvents (e.g. dimethylsulfoxide and 2-methyl-2-butanol) as a general strategy to acylate enzymatically hydrophilic substrates.We observed that decreasing the hydrophobicity of the medium (i.e. lowering the percentage of DMSO) the molar ratio sucrose diesters vs. sucrose monoesters can be substantially enhanced. The different regioselectivity exhibited by several lipases and proteases makes feasible to synthesize different positional isomers, whose properties may vary considerably. In particular, the lipase from Thermomyces lanuginosus displays a notable selectivity for only one hydroxyl group in the acylation of sucrose, maltose, leucrose and maltotriose, compared with lipase from Candida antarctica. We have examined three immobilisation methods (adsorption on polypropylene, covalent coupling to Eupergit C, and silica-granulation) for sucrose acylation catalyzed by T. lanuginosus lipase. The morphology of the support affected significantly the reaction rate and/or the selectivity of the process.

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The concentration of malonaldehyde (MDA) was measured in human erythrocytes obtained from subjects suffering from senile dementia of the Alzheimer type (SDAT), non-demented elderly subjects, and from young controls by two methods: high-performance liquid chromatography (HPLC) and the thiobarbituric acid (TBA) test. The MDA concentration measured by HPLC showed significant differences between SDAT and young control groups (p < 0.01) and between SDAT and non-demented elderly groups (p < 0.01), respectively. Nevertheless, significant differences were not exhibited between young control and non-demented elderly. Moreover, the rate of accumulation of TBA-reactive substances was not significantly different among the three groups. Our results indicate that the HPLC method is highly specific and accurate and distinguishes between true MDA and other aldehydes that may react with TBA. Significant increases in the concentration of MDA of SDAT subjects were found in comparison with the two other groups, indicating that the measurement of MDA in erythrocytes could be used as a marker of oxidative damage in Alzheimer’s disease.

Lipases from different origins have been immobilized in supports chosen by its different aquaphilicity and used as biocatalysts for the hydrolysis of tributyrin. The changes of the concentration of tri-, di-, monobutyrin, glycerol, and butyric acid during the reactions catalyzed by soluble, as well as immobilized, lipases were evaluated by gas chromatography. The experimental data were fitted to a simple kinetic model for the sequential reaction of tributyrin hydrolysis. The calculated apparent rate constants were different for the biocatalysts used and were apparently related to diffusional effects and aquaphilicity of the supports. Maximal yields of dibutyrin were found with the soluble Candida lipase, whereas the highest yield of monobutyrin (90%) was obtained with the least aquaphylic derivative (Candida-Celite).