Chiral analysis of amino acids from conventional and transgenic yeasts.

Autolysis of Saccharomyces cerevisiae yeast is the main source of molecules that contribute to the quality of sparkling wines made by the traditional method. In this work, a genetically modified yeast (LS11) is compared to its isogenic wild type strain (BY4741) after autolysis. Chiral micellar electrokinetic chromatography with laser-induced fluorescence detection (chiral-MEKC-LIF) is used to identify and quantify the main D- and L-amino acids from both strains after accelerated autolysis. The procedure includes amino acids extraction, derivatization with FITC and chiral-MEKC-LIF separation in a background electrolyte composed of 100 mM sodium tetraborate, 30 mM SDS, 20 mM beta-CD at pH 10.0. The D- and L-forms of Arg, Asn, Ala, Glu and Asp, corresponding to the major amino acids found in these samples, are separated in less than 30 min with efficiencies up to 800,000 plates/m and high sensitivity (i.e., LODs as low as 40 nM were obtained for D-Arg for a signal to noise ratio of three). From these results it is corroborated that the genetic modification brings a faster autolysis of the yeast, releasing a higher amount of L-amino acids to the medium in a short time. Interestingly, the pattern of release of D-amino acids was also different between the transgenic and the conventional yeast strains.