The Biosynthesis of Certain Gamma-Lactones from Glutamic Acid by Film Yeast Activity on the Surface of Flor Sherry

¹ CIBA-GEIGY Corp., P.O. Box 1830, Greensboro, NC 27419-8300
² Department of Chemistry, University of California, Davis, CA 95616
³ Department of Viticulture and Enology, University of California, Davis, CA 95616

Addition of I-2-¹⁴C-glutamic acid to simulated sherry under an actively growing film of Saccharomyces fermentati yielded, after extraction, radioactive gamma-butyrolactone, diethyl succinate, -ethoxy -butyrolactone, 4-hydroxy-5-oxohexanoic acid gamma-lactone, (4R,5S:4S,5R) 4,5-dihydroxy-hexanoic acid gamma-lactone, ethyl pyroglutamate, and an unidentified mixed ester, thus confirming their production from glutamic acid according to proposed pathways. When unlabeled glutamic acid was added to similar cultures, concentrations of the same compounds, along with 3-(methylthio)-propanol and an unidentified lactone, were enhanced. The 4R,5R:4S,5S isomers of 4,5-dihydroxyhexanoic acid gamma-lactone were found in a simulated sherry extract after three years of freezer storage, while only the 4R,5S:4S,5R enantiomeric pair was found in a fresh extract and separated by capillary GC.

Key words: biosynthesis, film sherry, gamma lactones, glutamic acid

Submitted on February 22, 1988