Inhibitory Effect of Fusarium Mycotoxins on Growth of Brewing Yeasts. 1 Zearalenone and Fumonisin B1*

Abstract

The Fusarium mycotoxins zearalenone (ZEA) andfumonisin B7 (FBj) added to the growth medium in low and high concentrations, were investigated as a possible cause of inhibition ofgrowth of Saccharomyces cerevisiae lager and ale strains. Toxic effects were assessed by measurement of dry weight or growth relative to controls, cell number, viability and conductance changes of the growth medium using indirect and direct methods. Hie Fusarium mycotoxins studied affected growth on brewing yeasts, but the inhibitory effect was dependent on concentration. Low concentrations (0.1-2 \iglml) had no significant effect on growth compared to controls. Although high concentrations of both mycotoxins strongly affected growth, the inhibitory effect depended on toxin concentration and type, yeast strain, length of incubation and method used to assess growth. The lowest concentrations ofmycotoxin causing significant inhibition on growth of these brewing yeasts were 50 \iglml ZEA for both yeast strains, and 10 \ig/ml FBj for the lager strain and 50 [ig/mlfor the ale strain.

The Microbiology of Malting and Brewing

“…The toxicogenic effects of DON and related mycotoxins are well established for animals and humans (for a review, see reference 165), leading to the adoption of strict quality standards for DON in malt. In addition to potentially threatening human health, high concentrations of these mycotoxins have been shown to inhibit yeast growth during beer fermentation (166,167).…”

Properties and Fermentation Activity of Industrial Yeasts Saccharomyces cerevisiae, S. uvarum, Candida utilis, and Kluyveromyces marxianus Exposed to AFB1, OTA, and ZEA

“…The variation in the mycotoxin effects in our study may partly be owed to the differences in the structure of the plasma membrane between the species and even between the strains of the same species (18).…”

“…Dziuba et al (5) reported strong inhibition of yeast growth by diacetoxyscirpenol (DAS), a trichothecenes mycotoxin, while ZEA and OTA had a weaker effect. Boeira et al (18)(19)(20) reported significant yeast growth inhibition by the Fusarium toxins, ZEA, DON, and fumonisin B1 (FB1). Similar findings were reported for the trichothecene, T-2 toxin by Foszczyńska and Dziuba (6), and some authors (5,8,17,21,22) have reported that mycotoxins inhibit alcohol dehydrogenase activity and consequently fermentation, lower CO2 release, and affect the production of volatile fermentation by-products.…”

Toxigenic fungi and mycotoxins in the barley-to-beer chain

“…Many factors influence the concentration in the final product (raw materials, production steps in the breweries such as the mashing step, fermentation, yeast type). They have been shown to disturb yeast metabolism during fermentation (Boeira, Bryce, Stewart, and Flannigan, 1999a, 1999bKoshinsky, Crosby, & Khachhatourians, 1992;Whitehead & Flannigan, 1989). Several mycotoxins, like trichothecenes, are water soluble and are extracted into wort during mashing.…”

“…Cantrell (2008) concluded that the majority (65-100%) of T-2 and HT-2 toxins present in malt persist into beer. The degree of growth inhibition has been shown to depend on the toxin concentration, yeast type, fermentation conditions and length (Boeira et al, 1999a(Boeira et al, , 1999bBoeira, Bryce, Stewart, Flannigan, 2002). Furthermore, mashing conditions and enzymatic activity may contribute to the release of mycotoxins from the grain matrix during mashing (Wolf-Hall, 2007).…”