Batch Fermentation Kinetics Of Bacillus Thuringiensis

Dipicolinate (DPA) is the important metabolite in the spore and its percentage keeps constant for the same bacterial. However, as for different strains and different culture condition, the relationship between the concentration of DPA and spore number was different. To validate this kind of relationship whether available under the different condition or not, data about DPA concentration and spore number from BMB005 cutivated in Hg> H9 as well as half of H8 cultures was managed through F test by SAS software. We got the result that environmental condition had no significant influence on the corresponding relationship of the concentration of DPA and spore number. As for BMB005, Equation y=L528x-96.19535 could represent this relationship under these three different condition (x denoted the concentration of DPA (ug/ml); y denoted spore number (X 107/ml)). Therefore, the concentration of DPA might give information about the spore concentration under the different condition for the same strain by this quick and accurate means during the industrial fermentation of Bacillus thwingiensis.Carbon metabolic model was developed for the vegetative growth phase and sporulation phase of Bacillus thuringiensis BMB005 in this research. This model mainly took cell growth, limiting-substrate consumption, production and consumption of PHB, and production of DPA as well as crystal proteins into account. Estimation of all these parameters and model validation were conducted using data from carbon-limited batch experiments by the software MATLAB 6.5. We found that the model successfully simulated the behavior of active biomass, PHB, DPA and crystal proteins and that the parameters such as Um, YX/G (1.1172 /h and 2.2928 g/g respectively) were also reasonable.These models hi this study well matched experimental data for the strain YBT1463, its no plasmid mutant BMB171 and BMB871 with only one plasmid named pBMBSOl encoding cry]Ac gene. It turned out that plasmid presence had positive effect on all these values of the parameters especially YX/G and Yp/o during the vegetative growth. It was suggested that plasmids in Bacillus thuringiensis did not cause the additional metabolic load on these cells. However, apparently, degradation of PHB regulated probably by plasmids also significantly affected spore synthesis metabolism with the exception of ^-endotoxin synthesis metabolism during the sporulation. This mechanism of action has not yet been definitively explained. The most important of all, we understood in this communication that how to regulate PHB synthesis and degradation by some means might be critical to radically ascertain its full-scale metabolism. It can further bring forward some favorable advice for boosting the yield of crystal toxin with the help ofcomparing the influence of plasmids on carbon metabolic kinetics for two phases in Bacillus thuringiensis.In the end, the research on DPA and crystal protein synthesis by feeding several metabolites during the different course of BMB005 fermentation was also studied. The results were as follows: glucose-fed at the given time could make the production of DPA and crystal protein increased; lactate-fed at these four phases led to the lowest yields of DPA and crystal protein; which were slightly raised by feeding sodium pyruvate and sodium succinate at the four courses. Feeding sodium acetate at the different phase might lead to the opposite results of the production of DPA and crystal protein, raised at a large scale at the stationary phase and diminished at the end of log-phase of fermentation.