Regulation of ethanolic fermentation in bell pepper fruit under low oxygen stress

Bell pepper fruit were stored under a continuous flow of 0 and 1% O-2 (balance N-2) or air for 7 days at 20 degreesC to study the regulation of ethanolic fermentation. The concentrations of ethanol and acetaldehyde were very low during storage at 1% O-2 and air. At 0% O-2, ethanol and to a lesser extent acetaldehyde, rapidly accumulated in the tissue. Pyruvate decarboxylase (PDC) activity greatly increased in fruit exposed to 1% O-2, while activity in fruit exposed to 0% was only slightly higher than that of the control. Alcohol dehydrogenase (ADH) activity greatly increased in fruit exposed to 1% but at 0% O-2 was at the same level as the control. The activity of ADH was about 10 times that of PDC during storage. Changes in ADH isozymes correlated well with changes in ADH activity. Concentration of NADH did not change during storage in air, but in fruit in 0 and 1% O-2 showed a significant increase. Concentrations of pyruvate were very low and did not change during storage at 1% O-2 and air. At 0% O-2, pyruvate rapidly accumulated in the tissue. The K-m of ADH in bell pepper fruit was 0.74 mM for acetaldehyde, and 0.33 mM for NADH. The K-m of PDC in bell pepper fruit was 0.92 mM for pyruvate. Possible regulation of ethanolic fermentation is briefly considered. (C) 2002 Elsevier Science B.V. All rights reserved.