Prevention of Aerobic Spoilage of Maize Silage by a Genetically Modified Killer Yeast,Kluyveromyces lactis, Defective in the Ability To Grow on Lactic Acid

ABSTRACT In this study, we propose a new process of adding a genetically modified killer yeast to improve the aerobic stability of silage. Previously constructed Kluyveromyces lactis killer strain PCK27, defective in growth on lactic acid due to disruption of the gene coding for phosphoenolpyruvate carboxykinase, a key enzyme for gluconeogenesis, inhibited the growth of Pichia anomala inoculated as an aerobic spoilage yeast and prevented a rise in pH in a model of silage fermentation. This suppressive effect of PCK27 was not only due to growth competition but also due to the killer protein produced. From these results, we concluded that strain PCK27 can be used as an additive to prolong the aerobic stability of maize silage. In the laboratory-scale experiment of maize silage, the addition of a killer yeast changed the yeast flora and significantly reduced aerobic spoilage.