Impact of kefir yeasts on Fusarium graminearum growth and production of deoxynivalenol

The kefir granules are a microbial consortium with numerous properties, among which their antifungal action has been reported. The aim of this research was to evaluate the antifungal capacity of yeasts isolated from kefir against Fusarium graminearum for its possible application as biocontrol agents. The inhibition of fungal growth was analyzed, according to dual tests, and the production of volatile organic compounds. The inhibition of the production of the mycotoxin deoxynivalenol was also analized. The six isolates studied belonged to the species Geotrichum candidum (2), Saccharomyces cerevisiae (1), Pichia kudriavzevii (2) and Pichia membranifaciens (1). They were isolated from kefir and identified in a previous work. The yeasts tested produced a reduction in the growth of F. graminearum in all assays. In particular, three of the isolates, 1 belonging to the species S. cerevisiae and 2 to the species P. kudriavzevii , generated volatile organic compounds that significantly inhibited the growth of the fungus in a 49.61, 51.46 and 49.61% respectively. The yeasts produced an inhibition of the mycotoxin deoxynivalenol correlated with a reduction in the growth of the fungus. The isolates of Geotrichum candidum (Gc30) and Pichia kudriavzevii (Pk27, PK20) significantly reduced the deoxynivalenol content of F graminearum by 86, 89 and 88%, and the range of growth inhibition in the assay was 16 to 62%. The data obtained about yeasts of novel origin are promising for their possible use as fungal biocontrol agents in foods as an alternative to agrochemicals