Characterization study of the sporulation kinetics of Bacillus thuringiensis

A wild-type and an rDNA strain of Bacillus thuringiensis were cultured in a net-draft-tube modified 20-L airlift bioreactor. A comparison of the sporu lation patterns suggests that the early sporulation strain has a lower fina l spore count. Results from off-gas analysis suggests that the CO2 profile could be an alternative indication to spore counts for the examination of f ermentation performance or even the mortality in bioassay of the cultivatio n product. The difference in mortality tests exhibited by the microorganism was attributed to different patterns of sporulation as well as different l evels of gene control inside the cell itself. The sporulation kinetics of B . thuringiensis was simulated by a simple modified Hill equation, where the initial glucose concentration could affect the timing of the onset of spor ulation. The equation matches well with the experimental sporulation data f or B. thuringiensis in both wild-type and rDNA strains. (C) 2000 John Wiley & Sons, Inc.