Site-specific natural isotope fractionation measured by deuterium NMR (SNIF-NMR) was used for investigating the deuterium transfers occurring in the fermentation of sugars into ethanol. In contrast to carbon-13, which is usually assumed to be randomly distributed within the glucose skeleton, very large deviations with respect to a statistical repartition are determined for deuterium. By transforming glucose samples from different origins into acetates and nitrates, the absolute values of the D/H ratios in the nonexchangeable sites were obtained. The hydroxyl sites were considered to contribute to the isotope content of the starting water medium. The site-specific isotope parameters were determined for more than 50 ethanol samples obtained by fermenting glucose samples issued from different starches and sucroses in water media with different isotope ratios. Several concentrations of sugar, several strains of the same yeast, and different temperatures of fermentation were considered. The whole set of isotope parameters characterizing the nonexchangeable sites of glucose, the starting and end water media, and the methyl and methylene sites of ethanol was submitted to factor analysis. The results are satisfactorily reproduced on the basis of two main factors which may be associated with the independent contributions of the isotope ratios of glucose and water. The isotope parameters of the end products and of the starting materials were then considered to be related by a set of linear equations and the coefficients of the redistribution matrix were calculated by multidimensional analysis. Thus the isotope ratio of the methyl site of ethanol exhibits a strong sensitivity toward the nonexchangeable sites of glucose and depends to a lesser extent on the isotope content of the starting water medium. By contrast, no direct connection is found between glucose and the methylene site which is only sensitive, with a strong discriminating effect against deuterium, to the isotope content of water. A redistribution coefficient slightly less than unity (0.96 for a concentration of sugar of 100 g L-I) is found between the isotope ratio of the end and starting water media. Although the bioconversion of glucose into ethanol occurs with high fractionation effects which are the source of high deuterium depletions in the methyl and methylene sites of ethanol as compared to glucose, constant redistribution parameters can be obtained in appropriate conditions and the isotope parameters measured in alcohols may be used as a fingerprint for characterizing the sugar and aqueous juice from which they have been produced. The site-specific natural isotope-parameters of ethanol therefore constitute a faithful and powerful probe for investigating the physiological biochemical and climatological effects which have governed the photosynthesis of sugars in natural conditions.The first issue of this journal, which appeared in 1879, began with a paper by D. P. Ricketts' which was devoted to the characterization of sugars from different origins. More t...

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