Biotechnological production of high specific activity L-35S-cysteine and L-35S-methionine by using a diploid yeast Saccharomyces cerevisiae

Article abstract of DOI:10.1002/jlcr.2580340612

High specific activity L-³⁵S-cysteine and L-³⁵S-methionine were synthesised by using a wild type diploid strain of baker's yeast- Saccharomyces cerevisiae. Yeast cells were grown in a sulphur depleted synthetic medium in which Na₂³⁵SO₄ (50 mCi/ml) was supplemented as the sole sulphur source. The level of incorporation was 60% on an average. The protein hydrolysate of the cultured cells was subjected to paper and column chromatographic separations to get the individual L-³⁵S-aminoacids. The radiochemical yields of cysteine and methionine were 6-7% and 18-20% respectively. The radiochemical purity of the products was >95%. The highest specific activity for the products obtained by employing this method was 1100 Ci/mmole from the starting material, Na₂³⁵SO₄, with a specific activity of 1350 Ci/mmole.