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

Abstract

AbstractHigh specific activity L‐35 S‐cysteine and L‐35 S‐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 Na2 35 SO4 (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‐35 S‐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, Na2 35 SO4, with a specific activity of 1350 Ci/mmole.