1994 Volume 58 Issue 7 Pages 1302-1305
The possibility of using lysine-accumulating yeast cells as a rumen-stable source of lysine for ruminants was investigated. The Saccharomyces cerevisiae strain AJ14599 accomulated free lysine amounting to 15% of the dry weight of the cells when cultured in a medium with the lysine precursor, L-α-aminoadipate (AAA). A mutant, LA-1, which was induced from AJ14599 and resistant to S-(β-aminoethyl)-cysteine (AEC), accumulated 4% free lysine in AAA-free medium. In both LA-1 and AJ14599 cells, more than 90% of the free lysine was in vacuoles. In an in vitro evaluation, the intracellular lysine was stably maintained and protected from microbial degradation during incubation in intact rumen juice, but it was immediately and completely released in a digestive enzyme (pepsin) solution. Lysine in LA-1 cells was also nutritionally available for weanling rats. Thus, lysine-accumulating yeast cells were effective for use as a rumen-stable source of lysine.
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