Identification of Levica yeasts as a potential ruminal microbial additive

Abstract

The objective of this study was to identify and characterize yeast strains isolated from the ruminal ecosystem that are capable of enhancing fermentation in bovines that consume high-fibre diets recommended by livestock feed guidelines in Cuba. The yeasts were isolated from the rumen of Holsteincows that had been fed a biofermented product. Isolated colonies were purified, identified, and characterized using biochemical and molecular methods, and their effects on ruminal fermentation were compared by measuring in vitro gas production. Thirteen new strains enhancing gas production with potential use as additives in ruminal fermentation were identified and named Levica. These strains grew successfully in detection medium for non-Saccharomyces wild yeasts and had long survival periods in the rumen. PFGE analysis found four karyotypes and homology of D1/D2 domain of gene 26S rDNA sequence was similar to that of I. orientalis, R. mucilaginosa, P. guilliermondii, and C. tropicalis. Phylogenetic analysis classified the strains into clades A and B. Clade A was further divided into groups AI, AII, BI, and BII. The AI cluster contained Levica (L)23, L24, L29, L33, and formed a monophyletic group with I. orientalis, while group AII contained L18 and formed a monophyletic group with R. muciloginosa. The BI cluster contained L13, L15, L17, L27, L28, and L32, all derived from P. guilliermondii. Cluster BII was composed only of L25 located in a separate subclade, forming a monophyletic group with C. tropicalis. The most useful strain for preparing microbial feed products to improve ruminal fermentation was L25 because it showed an increase in gas production.

Keywords

• fermentation
• bovine
• rumen ecosystem