Killer yeasts as antifungal biocontrol agents
The ability of killer yeast to inhibit the growth of fungi, specifically wood decay fungi, has been investigated. An initial broad screen of 17 yeast versus 17 fungi demonstrated that killer yeast can and do exhibit antagonistic as well as growth stimulatory affects on fungi. Yeast from the Saccharomyces and Pichia genera exhibited the greatest and broadest spectrum o f antagonism towards fungi and two yeasts one from each genus were studied further, namely Saccharomyces cerevisiae K28 and Pichia anomola NCYC 750. Both yeast showed evidence of affecting fungal growth through the secretion o f volatile chemicals. Partially concentrated cell free supernatant from the two yeasts also displayed antagonistic properties towards fungi demonstrating that a substance exhibiting antimycotic properties is secreted during the growth of the two yeasts. The mechanism by which this antimycotic activity was mediated by the yeast Pichia anomola NCYC 750 was identified to be associated with a 27 kDa exoglucanase enzyme. The possibility that the antimycotic activity observed is associated with yeast killer toxins is discussed.
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