Effect of crotonaldehyde on the metabolism of Candida utilis during the production of single cell protein from ethanol.

The effect of 20 low-boiling compounds on the yeast Candida utilis 49 was assessed by a screening test on agar medium. The highest toxicity was exhibited by crotonaldehyde, allyl alcohol and acrolein. Oxidation and assimilation experiments in a slightly aerobic environment showed that an increase in the level of crotonaldehyde in the medium in the range of 10--20 mg 1-1 brings about a lowering of intensity of metabolic processes in Candida utilis, suppression of ethanol utilization and aerobic oxidation rate, a drop in biomass yield, prolongation of cultivation time, etc. The inhibitory effect of crotonaldehyde depends strongly on the manner of its dosage into the medium (single or continuous) and other cultivation conditions (intensity of medium aeration, physiological state of the culture, etc). Crotonaldehyde is lost from the medium partially by volatilization and partially due to chemical and biochemical transformation.