Abstract: The production of natural delta-decanolide and/or delta-dodecanolide or mixtures thereof, by means of the biohydrogenation of a substrate containing the corresponding unsaturated lactones, delta-decen-2-olide and delta-dodecen-2-olide, respectively, and mixtures thereof, is performed by means of the use of a microorganism chosen from the group consisting of Saccharomyces delbrueckii, Pichia ohmeri, Hansenula anomala, Pichia stipitis, Debaromyces hansenii, Zymomonas mobilis, Zygosaccharomyces rouxii, Schawnniomyces occidentalis, Sarcina lutea and Geotrichum candidum.

Abstract: Process for the production of gamma- or delta-lactones according to the general formula: ##STR1## in which R is a saturated, mono-, di- or triunsaturated linear alkyl chain comprising from 2 to 10 carbon atoms and in which R.sub.1 is alkylene comprising 2 or 3 carbon atoms, entailing the operation which consists in culturing, in a substrate comprising a hydroxide or hydroperoxide of linoleic acid or of linolenic acid, of their esters or of their glycerides, or of an oleic acid derivative obtained by the photooxygenation of oleic acid or autoxidation of fats which contain it, a microorganism capable of performing beta-oxidations of said substrate.

Abstract: The process for the microbiological production of gamma (R) decanolide and/or gamma (R) octanolide involves the culture of a micro-organism selected from the group comprising Aspergillus niger, Cladosporium suaveolens, Phanerochaete chrysosporium and Pichia etchellsii in a culture medium that includes a vegetable oil, particularly castor oil, sunflower oil and coconut oil and their hydrolysates.