Kinetics of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> var. <Emphasis Type="Italic">israelensis</Emphasis> growth on high glucose concentrations |
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Authors: | M A Berbert-Molina A M R Prata L G Pessanha M M Silveira |
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Institution: | Laboratório de Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, CEP 28013-602, RJ, Brazil. mberbert@uenf.br |
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Abstract: | The kinetic and general growth features of Bacillus thuringiensis var. israelensis were evaluated. Initial glucose concentration (S
0) in fermentation media varied from 10 to 152 g/l. The results afforded to characterize four morphologically and physiologically
well-defined culture phases, independent of S
0 values: Phase I, vegetative growth; Phase II, transition to sporulation; Phase III, sporulation; and Phase IV, spores maturation
and cell lysis. Important process parameters were also determined. The maximum specific growth rates (μ
X,m) were not affected with S
0 up to 75 g/l (1.0–1.1 per hour), but higher glucose concentrations resulted in growth inhibition by substrate, revealed by
a reduction in μ
X,m values. These higher S
0 values led to longer Phases III and IV and delayed sporulation. Similar biomass concentrations (X
m = 15.2–15.9 g/l) were achieved with S
0 over 30.8 g/l, with increasing residual substrate, suggesting a limitation in some other nutrients and the use of glucose
to form other metabolites. In this case, with S
0 from 30.8 to 152 g/l, cell yield (Y
X/S
) decreased from 0.58 to 0.41 g/g. On the other hand, with S
0 = 10 g/l growth was limited by substrate, and Y
X/S
has shown its maximum value (0.83 g/g). |
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Keywords: | |
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