PROTEIN RELEASE AND FOAMING IN ESCHERICHIA-COLI CULTURES GROWN IN MINIMAL MEDIUM

Protein release was studied in Escherichia coli cultivations in minima l medium under different conditions. The energy source concentration w as oscillating either due to the cultivation technique or due to an ap plied on/off feed rate concept in fed-batch cultivations. It was found that the magnitude of protein release was dependent on the cultivatio n technique and the strain. The use of batch technique resulted in hig hest specific rate of protein release compared to fed-batch cultivatio ns. No dependence of protein release on oscillating glucose concentrat ion could be distinguished with oscillating periods of minutes of carb on starvation. Proteins released by cells acted as foaming agents and caused stabilisation of foam, during cultivation of Escherichia coli g rown in minimal medium. Since the total cell protein was reflected in the medium the protein release is considered to be caused by cell lysi s. However, only a few dominating proteins were present in the foam.