PRODUCTION OF THERMALLY-INDUCED RECOMBINANT PROTEINS RELATIVE TO CELLBIOMASS IS INFLUENCED BY CELL-DENSITY IN ESCHERICHIA-COLI BATCH CULTURES

Fed-batch cultures of recombinant Escherichia coli were studied regard ing their ability to permit CI857(ts)-controlled gene expression at di fferent growth phases. Cells, growing at 50% pO(2) and 28 degrees C in a bioreactor, were transferred to a shaker flask at 42 degrees C and the product yield was analysed after a short incubation time. Within t he batch period, the synthesis of recombinant beta-galactosidase relat ive to the increase of biomass during the induction period was enhance d in an biomass-dependent fashion. Whereas in young cells biomass prod uction dominates over recombinant protein production, the available en ergetic resources of aged eels seem to be employed more efficiently fo r CI857-controlled biosynthesis of recombinant proteins than of cell m aterial. A model to describe this 'altruistic' behaviour of old cultur es is here proposed.