Correlation of theoretical and experimental yields of phenylalanine from non-growing cells of a rec Escherichia coli strain

Abstract

Phenylalanine production from an auxotrophic plasmid-harboring Escherichia coli mutant ( E. coli W3110 Δ trp, Δ tyr, Δ phe/pJN6 carrying the genes aroF, pheA FBR, Tc R and Ap R) was studied in batch cultures. Phenylalanine was produced in the stationary phase due to the release of feed-back inhibition after depletion of tyrosine. The physiological state of the inoculum seriously affected the kinetics of phenylalanine production. The specific rate of phenylalanine production reached a maximum directly after cessation of growth and the production continued for at least 40 h. During an interval in this period the specific rate of phenylalanine production remained constant while the specific rate of glucose consumption decreased resulting in a yield of phenylalanine from glucose (0.27 g g −1) that corresponded to the estimated maximum theoretical yield coefficient. Detailed analyses of carbon balances showed that before and after this period a by-product not coupled to carbon dioxide production was formed. During the specific interval all glucose consumed was finally recovered in produced phenylalanine and carbon dioxide. This situation can only be achieved with non-growing cells.