The objective of this study was to investigate an effect of magnesium (MgCl₂·6H₂O) added to the culture medium on the growth of inoculum and the fermentation properties of brewer’s yeast Saccharomyces cerevisiae, strain N°1 (originating from the authors’ own collection). Two culture media were used to grow inoculum: YPG, which was a control medium, and a brewer’s wort. The two media were enriched with magnesium by adding 1.25 g Mg/dm³ to them. The yeast cultures were developed using the following methods: a) a stationary method – 48 hrs; b) a method with the aeration during a period of 24 hrs and 48 hrs; c) a method with the aeration during the 24 hrs, the next 24 hr period without aeration; at 28°C, and with a pH value equaling 5,0 in the case of the YPG, and 5.5 in the case of the wort. According to what has already been proved in previous experiments, the rate of magnesium being absorbed by cells was very high, and, at the same time, the biomass yield of yeast was low. It was stated that regardless of the type of medium, the enrichment with magnesium stimulated the growth and biomass of the yeast; the biomass yield was higher on the YPG medium than on the brewer’s wort. Furthermore, the magnesium was better absorbed by cells in the YPG medium. When inoculum grown on the brewery wort was used, the level of the brewery fermentation was higher, although the increase in the content of magnesium in the yeast was of no significant effect.