Yeast Potassium Nitrate Nitrogen Base contains Potassium Nitrate as a sole nitrogen source to test nitrogen assimilation. The addition of a carbon source is required. Histidine, Methionine and Tryptophan concentrations has been reduced to 10% of their original concentration as present in Yeast Nitrogen Base.
Yeasts which have grown on a rich medium like Yeast Agar may carry a reserve of nitrogen in the form of protein. To avoid errors due to this reserve of nitrogen it is advised to make two serial transfers in the medium. Seven days after the first inoculation the second inoculation is made in the same medium. If a positive result is obtained after seven days, the yeast cells assimilates nitrate as sole nitrogen source.
Suspend 2.7 gram powdered medium in 1 litre distilled water
Store dry at room temperature