Organic or mineral nitrogen source during Penicillium camembertii growth on a glucose limited medium

Penicillium camembertii was cultivated on a carbon-limited medium (glucose). Two nitrogen sources were compared, a mineral, ammonium, and an organic nitrogen source, lysine. Among the amino acids convenient nitrogen sources for P. camembertii, lysine was chosen since it cannot be assimilated as a carbon source for cell biosynthesis. During culture on glucose and ammonium, a decline phase immediately followed growth after glucose depletion, since no energy source remained in the medium. On the contrary, on glucose and lysine, a stationary state was recorded after glucose depletion, since lysine was used as the energy supply for cell maintenance, leading to the release of the corresponding carbon as CO2, while nitrogen from lysine was released as ammonium.