Indirect estimation of Bacillus thuringiensis var. israelensis biomass concentration using oxygen balance data

The kinetic analysis of Bacillus thuringiensis var. israelensis (Bti) growth is often hindered by the impossibility of using conventional methods to measure biomass concentration in natural raw-material-based media, which normally have a high content of insoluble solids. In this work, application of a mathematical model based on respiratory parameters in the estimation of Bti biomass concentration was evaluated. The values obtained for the respiratory parameters true cell yield from oxygen consumption and maintenance coefficient for oxygen (m(O)) were 0.091 g cell/mmol O-2 and 2.1 mmol O-2/g cell/hour, respectively. With these constants and the oxygen uptake rates obtained from oxygen balance calculations, cell concentrations of Bti were estimated in batch runs with initial glucose concentrations from 10 to 80 g/L and were found to be in good agreement with experimental data.