13C-Pattern of Natural Glycerol: Origin and Practical Importance

The average δ 13 C-value of glycerol from plant origin is 4−5‰ more negative than that of carbohydrates from the same source. This depletion is exclusively dealing with position C-1 of the molecule. This is also observed for glycerol from other natural sources, although to a smaller extent, while synthetic glycerol shows a statistical 13 C-pattern. On the basis of these data an illegal addition of glycerol to wine should be detectable. In fermentations of glucose with yeast the extent of the depletion in position C-1 of glycerol proved to be reciprocal to its yield. Furthermore a total carbon and isotope balance showed that the depletion of glycerol is a compensation for small 13 C-enrichments in the corresponding positions of main products. An isotope effect on the aldolase reaction and a noncomplete equilibration of the triose phosphates are discussed as main reasons for these findings.