LAUSR

Kluyveromyces marxianus yeast is often isolated from dairy products and used as probiotic agents in food. As a producer-yeast they must be genetically stable, have simple nutrient requirements, be effective in hostile conditions, grow on inexpensive nutrient media and be easy to store and distribute. Nineteen strains of K. marxianus isolated from natural biotopes were tested for their ability to grow on various carbon sources. For this, the YPD medium (1% yeast extract, 2% peptone, 2% dextrose, pH 5.5) was used with the addition of 20 g/L of one of the following carbon sources: glucose, sucrose, lactose, maltose, mannitol, arabinose, xylose, and galactose. The cultivation was carried out for 1–3 days. All isolates were also tested for their ability to grow in YPD broth at different temperatures (4, 27, 37, 40, 42, 46 and 48 °C) and pH (5; 3 and 2). K. marxianus strains showed widespread use of the substrate and high resistance to elevated incubation temperatures. All tested strains grew at 27 and 37 °C and one strain grew at 46 °C. None of the strains showed active growth at pH 2 and all cultures grew actively at pH 3. At the same time five strains showed growth at pH 5.0. All strains fermented galactose, 16 - xylose, 9 - glucose, 7 - lactose, 12 - maltose, 11 - arabinose, 5 - sucrose, 13 - mannitol. It should be noted that all strains in this study have showed fully restored growth after 2 hours’ incubation at pH 2. It indicates that they could survive when passing through the gastric passage into the intestine. These properties make the use of K. marxianus and its metabolites indispensable in agriculture as a feed additive. This work was supported by the Ministry of Science and Higher Education of Russia.