To Örebro University

The ascomycetous yeast Pichia anomala J121, inhibits mould growth in malfunctioning airtight storage systems for moist animal feed grain. Extensive studies of P. anomala J121 have given detailed knowledge of growth physiology and limiting environmental factors, which is necessary to understand the inhibitory activity. Our main objective is to identify the mechanisms behind the inhibitory activity. We have two non-exclusive working hypothesis: ^I)P. anomala produces antifungal substances and ^II)P. anomala out-competes the mould for space, nutrients, and oxygen. We have found that volatile metabolites restrict radial growth and sporulation of moulds in mouth-to-mouth assays where agar plates are placed facing each other with the yeast inoculated on the upper plate and the mould on the lower. Previous studies of P. anomala have shown that it produces high quantities of ethyl acetate - a mould-inhibitory substance. We are working to identify homologous genes in P. anomala J121 to the acetyltransferase encoding genes ATF1 and ATF2 in Saccharomyces cerevisiae. Another approach has been to identify intra- and extracellular metabolites during aerobic and oxygen limited growth. Intracellular metabolites were identified by Magic Angle Spinning-High Resolution-Nuclear Magnetic Resonance (MAS-HR- NMR) that allows analysis of living cells. Extracellular metabolites were analysed with HPLC. Glycerol, well known for its role during osmotic stress, is accumulated in response to oxygen stress.