Glucose and ammonium limitation

In comparison with oxygen, ammonium is absolutely required for growth if no other nitrogen source is available. In fact it is a non-substitutable nutrient for biosynthesis whereas oxygen is an electron acceptor that can be substituted by glucose (reduced to ethanol). If glucose conversion is not complete due to ammonium limitation, the restriction of ammonium supply compared to glucose uptake is expressed as  

Four observations were made from experiments performed with S. cerevisiae and K. marxianus grown in continuous cultures on glucose with different ammonium feed concentration [39-41]  

Calorimetric measurements are used in addition to other on-line measurements such as roj, rcoj, PO2 or pH evolution. The information is both qualitative, to detect physiological events, and quantitative. 

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