AhmadWeek3

Part 1: Experimenting with different levels of ammonia

• Saccharomyces cerevisae, a type of yeast, uses ammonia as its primary nitrogen source
  • Past research has shown that ammonia concentration affects growth
  • In this paper, the researches wanted to know if ammonia flux, and not concentration, is the limiting factor
• Physiological Parameters
  • S. cerevisae was first grown in cultures with different levels of ammonia, but fixed glucose concentrations
  • Increases in the ammonia concentration from 29 to 61 mM showed a change in biomass from 4.9 to 8.2 g/L
  • After 61 mM, however, there was no significant increase in biomass
  • Formula to calculate ammonia flux: [dilution x (input ammonia concentration - residual ammonia concentration)/biomass]
  • At a level above 44 mM, oxygen consumption was equal to carbon dioxide production
• Ketoglutarate, Glutamate, Glutamine concentrations as ammonia concentrations were increased
  • Ketoglutarate: Decreased
  • Glutamate: Increased
  • Glutamine: Increased
• Figure 1
  • X axis: NH4 concentration
  • Y axis:
    • A: Residual NH4 concentration
    • B: 02 consumption/CO2 production
    • C: Ketoglutarate, Glutamate, Glutamine concentrations