Abstract
Fungicides, particularly those used during grape maturation, as captan, can affect the natural yeast population of grapes, and can reach grape must affecting wine fermentation. The objective of the present work was to study the effect of captan on the viability and fermentative behavior of S. cerevisiae . S. cerevisiae (BY4741) on exponential phase was treated with captan (0 to 40 μM) for different periods, and their cell viability analyzed. Cell membrane integrity, thiols concentration, and reactive oxygen species (ROS) accumulation was determined. The fermentation experiments were conducted in synthetic must using wine yeast strain Y904. The results showed that under aerobic conditions, 20 μM of captan reduce 90% of yeast viability in 6 hours. Captan treated cells exhibited alteration of membrane integrity, reduction of thiol compounds and increase in intracellular ROS concentration, suggesting a necrotic and pro-oxidant activity of the fungicide. Fermentative experiments showed that concentrations above 2.5 μM captan completely inhibited fermentation, while a dose dependent fermentation delay associated with the reduction of yeast viability was detected in sub-inhibitory concentrations. Petit mutants increase was also observed. In conclusion, the captan induces yeast necrotic cell death on both aerobic and anaerobic conditions causing fermentation delay and/or sucking fermentations.
Highlights
Captan (N-cyclohex-4-ene-1, 2-di carboximide) is a broad spectrum fungicide of the phtalimide class, widely used to control several grapevine diseases, as downy mildew, phomopsis, black rot, ripe rot, and bitter rot
Captan reaction with thiol groups has been pointed as the main mode of action on phytopathogenic fungi, been responsible for the reduction of enzymatic activities, respiration, physiological changes, and fungal death [3]
In vitro genotoxicity studies indicated that phtalimide fungicides were associated to point mutations, and gene conversion [5, 6], been classified as potential human carcinogen
Summary
Captan (N-cyclohex (trichloromethylthio)-4-ene-1, 2-di carboximide) is a broad spectrum fungicide of the phtalimide class, widely used to control several grapevine diseases, as downy mildew, phomopsis, black rot, ripe rot, and bitter rot. Captan reaction with thiol groups has been pointed as the main mode of action on phytopathogenic fungi, been responsible for the reduction of enzymatic activities, respiration, physiological changes, and fungal death [3]. In the presence of exposed thiol groups, captan oxidize thiols and is hydrolyze to its reactive thiophosgene (SCCl3) moiety, and the 1,2,3,6-tetrahydrophthalimide ring [4]. In vitro genotoxicity studies indicated that phtalimide fungicides were associated to point mutations, and gene conversion [5, 6], been classified as potential human carcinogen. Based on in vivo and molecular analysis in mammals they were re-classified as nongenotoxic [7]
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