Effect of ammonium ions on delta 5,7-sterol synthesis in Saccharomyces cerevisiae.

The effect of ammonium concentration in the medium on delta 5,7-sterol synthesis was examined. Higher concentrations of this nitrogen source in the medium decreased sterol synthesis and accumulation during growth. An intermittent supply with ammonium resulted in a proportional synthesis of delta 5,7-sterols and biomass. The carbon to nitrogen molar ratio of greater than or equal to 40 allowed the maximum accumulation of delta 5,7-sterols with our strain of baker's yeast.