Maintenance requirements in Bacillus sphaericus 1593M under dual substrate limitations estimated at zero growth rate in a total cell retention culture

Abstract

The maintenance requirement(s) exhibited by Bacillus sphaericus1593M was clearly established from the data on the steady state continuous cultures wherein the growth yield was found to be increasing with increase in dilution rate (4). In the present study we have attempted to estimate the maintenance coefficient of B. sphaericus 1593M by achieving zero growth rate in a total cell retention culture (TCRC). Zero growth rate was achieved at a cell density of 5.57 g l⁻¹ which remained constant reflecting a steady state in the TCRC. Based on the substrate flux calculations, maintenance coefficient was found to be 0.087 h⁻¹. Further, using this data of maintenance coefficient, steady state cell density and substrate profiles in continuous cultures of B. sphaericus 1593M were predicted by simulation, which showed a close relationship to that of the experimental data.