Stability of recombinant protein production by Penicillium chrysogenum in prolonged chemostat culture

Abstract

A strain (WKW2) of Penicillium chrysogenum transformed with heterologous fungal acetamidase ( amdS) and bacterial β-galactosidase ( lacZ) was grown at a dilution rate of 0.17 h −1 (doubling time of approx. 4.1 h) for 1600 h in a glucose-limited culture. By the end of the experiment the original strain had been almost completely replaced by spontaneous, morphological mutants, but the acetamidase and β-galactosidase activities of the culture were essentially unaltered. Furthermore, when WKW2 and the non-transformed parental strain (NRRL1951) were grown together in glucose- or NH 4 +-limited chemostat cultures, neither strain had a selective advantage over the other. Thus, heterologous gene expression does not result in NRRL1951 having a selective advantage over WKW2. These results suggest that continuous flow culture systems could be used for efficient (and cost effective) production of recombinant proteins.