Biology of Killer Yeast and Technological Implications
The killer phenomenon has been reported among various genera of yeast. Potential ability of certain yeast (killer yeast) to kill the other yeast (sensitive yeast) was first observed in the strains of Saccharomyces cerevisiae. The killer yeasts secrete ext
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Abstract The killer phenomenon has been reported among various genera of yeast. Potential ability of certain yeast (killer yeast) to kill the other yeast (sensitive yeast) was first observed in the strains of Saccharomyces cerevisiae. The killer yeasts secrete extracellular protein toxin that is fatal for the sensitive yeast, and kills the latter. Killer toxin producer yeasts are immune towards their own toxin but can kill the other sensitive yeasts by employing variety of mechanisms like targeting several cellular components viz. cell wall, plasma membrane, tRNA, DNA etc. The genetic information for production of killer toxin (killer phenotype) is generally present as extra-chromosomal genetic elements like dsRNA or linear DNA, or on the chromosome. The protein toxins produced by several killer yeasts have been thoroughly studied after purification and characterization. Killer toxins encoding genes have been cloned, characterized and expressed in heterologous systems. Significance of yeast-derived killer toxins and/or killer yeasts have been implicated in various areas including food fermentations/yeast-based bioprocesses. Yeast killer phenomenon may play a substantive role in stabilizing the ecosystem. Killer toxins of yeast may have potential for application as biopreservatives, biocontrol agents and as new therapeutic molecules especially against multidrug resistant pathogens. For ethanol-based industries like distilleries, breweries, and wineries, killer yeast can be employed as starter industrial yeast cultures to protect against the wild contaminants. Current article presents recent developments on biological and technological implications of killer yeasts. Keywords Killer yeast visiae Applications
Yeast killer toxin Receptor Saccharomyces cere-
B.K. Bajaj (&) S. Singh School of Biotechnology, University of Jammu, BAWE WALI RAKH, Jammu 180006, India e-mail: [email protected] © Springer Science+Business Media Singapore 2017 T. Satyanarayana and G. Kunze (eds.), Yeast Diversity in Human Welfare, DOI 10.1007/978-981-10-2621-8_7
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1 Introduction The origin of the word ‘yeast’ has been originated from a Dutch word ‘gist’ that means froth/foam produced due to metabolic activities of yeast during brewing (Hatoum et al. 2012). Yeasts, the eukaryotic microorganisms are extensively spread in various natural environments viz. the food products, fruits, vegetables, body surfaces of plants, animals and humans and several other ecological niches (Satyanarayana and Kunze 2009; Bajaj et al. 2013). Generally nutrient rich substrates are more frequently and rapidly colonized by yeasts. Yeasts are integral and very important components of several complex ecosystems especially due to their tremendous capability for potential interactions with other microorganisms of those ecosystems. The most common mode of vegetative growth of yeast is by budding but yeasts may have both sexual and asexual states. The genus Saccharomyces of the phylum Ascomycota is one of the most studied yea
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