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Acta Tropica
111, No. 1, 2009; Pages: 7 - 14

Photostabilization of Bacillus thuringiensis fermented wastewater and wastewater sludge based biopesticides using additives

K.D. Adjalle, S.K. Brar, R.D. Tyagi, J.R. Valéro, R.Y. Surampalli

INRS Eau, Terre et Environnement (INRS-ETE), 490, de la Couronne, CP 7500, Québec, Québec, Canada G1K 9A9.


Photoprotection (against UV-A and UV-B radiations) of the active components of Bacillus thuringiensis var. kurstaki obtained from the fermentation of various culture media was investigated. The culture media comprised: starch industry wastewater; secondary wastewater sludge (non-hydrolyzed and hydrolyzed) and soya (used as a reference). Photoprotection was carried out by using various UV-protection additives, namely, para-aminobenzoic acid, lignosulfonic acid and molasses at different concentrations (0.1%, 0.15% and 0.2%, w/w). In the absence of UV-protection agents, secondary sludge demonstrated natural UV protection with half-lives ranging from 3.25 to 3.4 d. The half-life for soya and starch industry wastewater was 1.9 and 1.8 d, respectively. Para-amino-benzoic acid as a UV-protection agent at 0.20% (w/w) gave excellent UV-protection for soya and starch industry wastewater with half-lives being 5.9 and 7 d, respectively. Likewise, lignosulfonic acid at 0.20% (w/w) was an effective photostabilizer for hydrolyzed and non-hydrolyzed secondary sludge with half-lives of 7.25 and 8 d, respectively. Hence, when similar concentration of the UV-protection additives was used, photoprotection was higher for the alternative media than the conventional soya medium, validating the technical feasibility of using three additives.

Keywords: Bacillus thuringiensis; Entomotoxicity; Secondary sludge; Starch industry wastewater; UV radiations



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