EFFECT OF ANTIFOAM AGENTS ON THE MEDIUM AND MICROBIAL CELL PROPERTIESAND PROCESS PERFORMANCE IN SMALL AND LARGE REACTORS

The influence of four antifoam agents (AFA): S184 (pure silicon oil), SLM54474 (polypropylene glycol; PPG), VP1133 (silicon oil/PPG mixture) , and SE9 (aqueous emulsion with 10% silicon oil component) of Wacker- Chemie Co., was determined on the foaminess of cultivation media of re combinant Escherichia coli, Penicillium chrysogenum and Cephalosporium acremonium. The effect of these AFAs was evaluated during the cultiva tion of recombinant E. coli on the following process variables: gas ho ldup, bubble velocity, oxygen volumetric mass transfer coefficient (K( L)a), cell mass concentration (X), specific growth rate (mu), product (fusion protein) concentration (P), specific product activity (SP), pl asmid stability, number of colony-forming units (CFU), specific glucos e uptake rate (SG), acetate production rate, oxygen transfer rate (OTR ), CO2 production rate (CPR) and respiratory quotient (RQ) The antifoa m agents in the following initial concentrations, 100 (VP1133), 300 (S LM54474), 1000 and 2000 ppm (S184) were effective in foam depressing d uring batch cultivation off. coli in small reactors and had a slight o r positive effect on process performance Their presence enlarged X and CFU. The addition of SLM54474 and/or VP1133 increased P and SP, and s lightly reduced Lc. Addition of S184 reduced P and SP but did not infl uence mu. In large reactors SE9 and VP1133 proved to be the most effic ient in foam suppression, but pure silicon oil (S184) and pure PPG (SL M54474) were inefficient.