Studies on the growth metabolism of Bacillus thuringiensis and its vegetative insecticidal protein engineered strains by microcalorimetry

The metabolic power-times curves of Bacillus thuringiensis and its vegetative insecticidal protein-engineered strains were determined at 30°C using a thermal activity monitor, air Isothermal Microcalorimeter, and ampoule method. From the power-times curves, the maximum power (Pmax) in the log phase, growth rate constant (k), generation times (tG), time of the maximum power (tmax), heat effects (Qlog) for log phase, and the total heat effect in 45 h (Qtotal) of. B. thuringiensis strains can be obtained. The results indicate that their power-times curves are different. The relationship between their metabolic power-times curves and character of bacteria metabolism, and thermokinetics and gene expression were analyzed and discussed. The character of the bacteria power-times curves reflected the physiologic character of gene expression. The microcalorimetric method proved to be a reliable and sensitive tool for the assessment of growth metabolism, heat output in bacteria and its engineered strains. The determination of the thermokinetic character is beneficial to the control of fermentation.