Studies into Saccharomyces cerevisiae baker's yeast capacity for binding magnesium under batch conditions
Duszkiewicz-Reinhard, W.E-mail:reinhard@alpha.sggw.waw.pl | Gniewosz, M. | Blazejak, S. | Bankowski, A.(Warsaw Agricultural University (Poland). Dept. of Food Biotechnology, Microbiology and Food Evaluation)
The capacity for natural binding of magnesium by baker's yeast (S. cerevisiae No. 102) was investigated under batch conditions (with aeration) on control medium (YPD) and experimental media enriched with Mg2+ ions at the following doses: 0.25 g/L, 0.5 g/L and 1.25 g/L. The source of Mg2+ ions were magnesium salts: MgSO4 x 7H2O or MgCl2 x 6H2O, which were added to the culture media at the beginning of incubation and at the end of the logarithmic growth phase of yeasts. Magnesium content was determined with the AAS method in non rinsed biomass (magnesium not permanently bound with cells) and biomass rinsed twice with deionised water (magnesium permanently bound with cells). There was more magnesium not permanently bound with yeast cells. The medium enriched with chloride salt was found to bind more magnesium ions than the medium supplemented with sulphate salt. The content of magnesium permanently bound with cell biomass obtained after 6h incubation with the addition of chloride salt (3.50 - 3.71 mg Mg/g d.s.) was twice as high as the content of magnesium bound with the biomass from control medium. The applied concentrations of Mg2+ ions had no significant effect on the content of magnesium permanently bound with cell yeasts. Magnesium addition to media at the end of the logarithmic growth phase was found not to increase magnesium content in the yeast cell biomass after 24h and 48h of incubation. The addition of magnesium chloride to YPD medium intensified considerably the growth rate between the 6th and 24th h of culture and had a positive effect on the final yield of yeast cell biomass
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