Growing cultures of Colletotrichum gloeosporoides CBS 193.32 reductively transformed sorbic acid 10 and the structurally related isomeric mono‐unsaturated acids 11 and 12 into the corresponding unsaturated and saturated alcohols. In the case of 10 and 12, there was accumulation in the fermentation medium of up to 25% and 10%, respectively, of the intermediate aldehydes 7 and 5. The process, if applied to acid 10 of extractive botanical origin, would represent an access to the natural forms of the C6 odorants (E,E)‐2,4‐hexadienal 7 and (E)‐4‐hexen‐1‐ol 9. Copyright © 1999 John Wiley & Sons, Ltd.