Simple technique for simultaneous on-line estimation of biomass and acetate from base consumption and conductivity measurements in high-cell density cultures of Escherichia coli.

In high-cell density cultures of Escherichia coli, the amount of ammonia required to maintain a constant pH was an effective on-line measure of biomass. When acetic acid formation occurred, biomass estimates were corrected by additional measurements of the culture conductivity. In the absence of acetic acid excretion, the culture conductivity decreased approximately linearly during the fed-batch phase of the high-cell density cultivation. Upward deviation of the culture conductivity from this trend was proportional to the acetate concentration in the medium. Thus, simultaneous determination of the acetic acid concentration and correction of biomass estimates from ammonia consumption were possible by conductivity measurements. Copyright 2000 John Wiley & Sons, Inc.