Combining solvent engineering and thermodynamic modeling to enhance selectivity during monoglyceride synthesis by lipase-catalyzed esterification.

Monoglyceride synthesis by Rhyzomucor miehei lipase was investigated via direct esterification between glycerol (adsorbed onto silica gel) and oleic acid in organic solvents. The main difficulty is to avoid the unwanted production of di- and tri-glycerides. It was demonstrated that an increase in solvent polarity, using mixtures of n-hexane and 2-methyl-2-butanol (2M2B), improves drastically the selectivity toward monoglyceride formation. In pure n-hexane, the monoglyceride represents only 6 molar % of the total products at the thermodynamic equilibrium (34 and 60% for di- and tri-glyceride respectively). Use of an equivolume mixture of n-hexane/2M2B enables a product mixture to be obtained containing 94% of monoglyceride at equilibrium (2.4 and 0% for di- and tri-glyceride respectively). This positive effect is counterbalanced by a decrease both in initial velocities and in substrate conversion at thermodynamic equilibrium.A modeling, able to predict the three thermodynamic equilibria governing the 3 consecutive reactions, based on activity coefficient calculations using the UNIFAC model, is proposed. It takes into account both the partition of water between solvent and immobilized catalyst, and the partition of glycerol between solvent and silica gel. A good correlation with experimental data obtained in n-hexane/2M2B mixtures was observed.

[Dementia syndrome and intercurrent pathologies in the elderly. A study of 100 patients over 75 years of age in a geriatrics internal medicine unit]. / Syndrome démentiel et pathologies intercurrentes chez les sujets âgés. Etude de 100 patients de plus de 75 ans en Unité de médecine interne gériatrique.

Elderly people with dementia are admitted in ever increasing number to Internal Medicine units for exploration of dementia and treatment of intercurrent diseases. The purpose of this prospective study of 100 demential subjects aged 75 or more (mean: 85.3 +/- 5.4 years) was to discover the cause of dementia, to investigate the associated diseases and to evaluate the effects of treatment of these pathologies on the patients' cognitive performance. The mean duration of stay in hospital was 25.5 +/- 14.5 days (extreme: 6-100 days); 69 returned home, 17 were institutionalized and 14 died. Dementia was degenerative and of the Alzheimer type (73%) with vascular lesions (24%) associated with brain tumours (2%) or normal-pressure hydrocephalus (1%). On average, 2 pathologies were associated with Alzheimer's dementia and 3.5 with dementia cum vascular brain lesions. Repeated evaluation of cognitive performance was carried out using Folster's Mini Mental Status (MMS), a global evaluation test. It showed that 18% of the patients were significantly improved while the other diseases were being treated. The hypothesis of regressive confusional elements superimposed on dementia is accepted by the authors as it fits the model of geriatric multipathology morbidity. Since there is no specific treatment for most types of dementia, particular attention must be paid to associated diseases likely to aggravate the clinical expression of dementia.