Inter-Strain Hybridization of Kluyveromyces lactis for creating efficient lactose-fermenting Yeast

Abstract

A molecular genetic study of Kluyveromyces lactis yeasts isolated from various dairy products in the countries of the former Soviet Union and other regions of the world has been carried out. Based on physiological tests, four strains were selected that carry different LAC loci and are characterized by good fermentation intensity: VKM Y-1339 (LAC3), VKM Y-1333 (LAC3), NRRL Y-1118 (LAC1), and NRRL Y-1140 (LAC2). Eleven hybrids of the selected strains with different rates of lactose fermentation were obtained. No correlation was found between the intensity of lactose fermentation and the amino acid sequences of the LAC12 lactose permease gene of the LAC1, LAC2, and LAC3 loci. Apparently, a specific combination of genotypes of crossed strains has a more significant effect on the fermentation activity. The results obtained showed that inter-strain hybridization of K. lactis dairy yeast is an effective method for creating new strains with high fermentation capacity. Hybrids H2-3 (NRRL Y-1118 × VKM Y-1333) and H3-3 (NRRL Y-1140 × VKM Y-1333) with the highest ability to ferment lactose are of interest for further molecular genetic research and breeding programs. Key words: Kluyveromyces lactis, β-galactosidase, lactose permease, LAC4, LAC12, LAC1 locus, LAC2 locus, LAC3 locus, inter-strain hybridization, lactose fermentation, heterosis Acknowledgment - The authors are grateful to the Genomic Center of the Kurchatov Institute SRC---GosNIIgentika for sequencing the nucleotide sequences of the LAC12 genes for lactose permease on the Applied Biosystems 3730 automated analyzer. Funding - This work was supported by an internal grant from the National Research Center Kurchatov Institute (order of the National Research Center Kurchatov Institute No. 1779).