TdKT, a new killer toxin produced by Torulaspora delbrueckii effective against wine spoilage yeasts

Abstract

Microbiological spoilage is a major concern throughout the wine industry, and control tools are limited. Thispaper addresses the identification and partial characterization of a new killer toxin from Torulaspora delbrueckiiwith potential biocontrol activity of Brettanomyces bruxellensis, Pichia guilliermondii, Pichiamanshurica and Pichiamembranifaciens wine spoilage. A panel of 18 different wine strains of T. delbrueckii killer yeasts was analysed, and the strain T. delbrueckii NPCC 1033 (TdKT producer) showed a significant inhibitory effect on the growthof all different spoilage yeasts evaluated. The TdKT toxin was then subjected to a partial biochemical characterization. Its estimated molecular weight was N30 kDa and it showed glucanase and chitinase enzymatic activities. The killer activity was stable between pH 4.2 and 4.8 and inactivated at temperature above 40 ° C. Pustulan andchitin - but not other cellwall polysaccharides - prevented sensitive yeast cells from being killed by TdKT, suggestingthat those may be the first toxin targets in the cell wall. TdKT provoked an increase in necrosis cell deathafter 3 h treatment and apoptotic cell death after 24 h showing time dependence in its mechanismsof action. Killertoxin extracts were active at oenological conditions, confirming their potential use as a biocontrol tool inwinemaking.