Influence of pH Control Agents on Entomotoxicity Potency of Bacillus thuringiensis using Different Raw Materials |
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Authors: | Abdessalem Yezza Rajeshwar D Tyagi José R Valéro Rao Y Surampalli |
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Institution: | (1) Terre et Environnement, INRS Eau, 490, Rue de la Couronne, G1K 9A9 Québec, Canada;(2) Centre Foresterie des Laurentides, Service Canadien des Forêts, Canada;(3) US Environmental Protection Agency , USA |
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Abstract: | Summary In this investigation, ammonium hydroxide and acetic acid were used as pH control agents during Bacillus thuringiensis (Bt) fermentation in a pilot scale fermentor (150-l) employing two secondary wastewater sludges from two different wastewater
treatment plants (CUQS and JQS) and semi-synthetic soybean meal medium as raw materials. Regardless of the cultivation medium,
a substantial increase in total cell count, spore count, protease activity and entomotoxicity was achieved when the pH of
the culture was controlled using NH4OH/CH3COOH. At harvest, total cell count increased by almost 17%, 33% and 25%; protease activity was enhanced by 12%, 33% and 53%
and maximal spore count augmented by almost 28%, 48% and 33% in CUQS, JQS and soybean medium, respectively. Entomotoxicity
potency was improved by 22%, 21% and 14% in CUQS, JQS and soybean medium, respectively compared to results obtained with NaOH/H2SO4 as pH control agents. A higher entomotoxicity was also observed using sludge compared to the soybean medium. This improvement
of the Bt process performance was a consequence of the addition of rapidly utilizable carbon and nitrogen source through pH
control, which stimulated endotoxin production in the crystal and enhanced sporulation. |
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Keywords: | Bacillus thuringiensis entomotoxicity pH control protease activity sporulation wastewater sludge |
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