Abstract
BackgroundEcological killer yeasts have had few studies compared with laboratory killer yeasts. The killer yeasts are known in excreting killer toxins that kill sensitive or susceptible yeasts. The killer toxins, such as TK and WK excreted from two yeast isolates (Torulaspora delbrueckii and Wickerhamomyces anomalus) have protenious nature with different molecular weight depending on yeast species.ResultsA qualitative test was conducted to determine the ability of both isolates to produce killer toxins on the media of yeast extract and malt extract broth when the two toxins were first purified by ammonium sulfate salt at 40% concentration and then by dialysis for the killer toxin TK and gel filtration method for WK. The molecular weight of TK was estimated at about 15 kDa, while WK was at 45 kDa. The chemical properties of the killer toxins were also studied. The results showed that the two killer toxins were with protenious nature.ConclusionBoth yeast isolates (Torulaspora delbrueckii and Wickerhamomyces anomalus) had the ability of producing different kinds of killer toxins. The two killer toxins (TK and WK) were identified for the first time in Iraq, and their production involves many steps of economically unexpansive purification method with a good quality and high purity of producing killer toxins. The results confirmed that the nature of killer toxins (WK and TK) was similar to protein compounds resulted from the transition in UV and functional groups.
Highlights
Killer yeasts are known in excreting killer toxins that kill sensitive or susceptible yeasts (Becker and Schmitt 2017)
The individual antifungal activity of each part of these protein peaks, only the first peak was contained the killer toxin (WK), while the other peaks were not showing any biological activity. This indicates that the killer toxin (WK) was fully separated at the first peak, and the toxin had a high molecular weight compared to the rest of other separated proteins
The molecular weight of killer toxin in the strain 28 (KT28) of S. cerevisiae was measured at 16 kDa, which is conformed to the findings revealed in the above study
Summary
Killer yeasts are known in excreting killer toxins that kill sensitive or susceptible yeasts (Becker and Schmitt 2017). Regarding the characteristics required to conduct alcoholic fermentation in industry for the non-Saccharomyces yeasts such as T. delbrueckii and W.anomalus that are identical to the referent, best-deemed, S. cerevisiae. As a result based on this background, the authors of this study were searching for killer toxins originated from ascomycetous yeasts in soil by using two type strains (Torulaspora delbrueckii and Wickerhamomyces anomalus) as examined strains. The killer yeasts are known in excreting killer toxins that kill sensitive or susceptible yeasts. The killer toxins, such as TK and WK excreted from two yeast isolates (Torulaspora delbrueckii and Wickerhamomyces anomalus) have protenious nature with different molecular weight depending on yeast species
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