Probiotic Yeast and their Impact in EM

  • 12 December 2019

EM is a multi-species, multi strain blend of beneficial naturally-occurring organisms that can be applied as inoculants to increase the microbial diversity of soil ecosystem. The inoculant is widely reported to consist mainly of the photosynthesizing bacteria, lactic acid bacteria, yeasts, actinomycetes and fermenting fungi but it is not limited to these microbes. These microorganisms are physiologically compatible with one another and can coexist in liquid culture. The real benefits however are in the impact each of these remarkable microbes has on the soil and on each other. In this blog series we are going to breakdown each group looking at the function of these unique microbes.

Another group of organisms found in EM include several species of probiotic yeasts. These yeasts are crucial as they synthesize antimicrobial and other useful substances required for plant growth from amino acids and sugars secreted by bacteria, organic matter and plant roots. Bio-active substances such as hormones and enzymes produced by yeasts promote active cell and root division. Their secretions are useful substrates for the other microbes in EM such as lactic acid bacteria and actinomycetes. A growing number of studies indicate that plant root growth may be directly or indirectly enhanced by yeasts in the rhizosphere. Species including the yeasts present in EM are able to nitrify ammonium to nitrate via nitrite in vitro (Al-Falih, 2006). Whereas the ascomycetous genera Williopsis and Saccharomyces were able to oxidize elemental sulfur in vitro to produce phosphate, tetrathionate, and sulfate (Al-Falih and Wainwright, 1995).

Saccharomyces cerevisiae are particularly active in the quick conversion of sugars into alcohol and carbon dioxide, thus contributing to the limited availability of nutrients for other organisms inhabiting the plant organs. In addition, they are capable of producing so-called “toxin killers” which, as protein complexes, exhibit very strong inhibitory properties of pathogens located in the same environment.

This amazing yeast has many interactions with bacteria, other fungi and higher eukaryotes. This is shown in the below image:


Nitrification, S-oxidation and P-solubilization by the soil yeast Williopsis californica and by Saccharomyces cerevisiae

Effect of soil amendment with yeasts as bio-fertilizers on the growth and productivity of sugar beet



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