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    Impact of Tween 80 during Bacillus thuringiensis fermentation of wastewater sludges

    Year: 2005

    Journal: Process Biochemistry 40 (2005) 2695-2705, 20111221

    Authors: S.K. Brar , M. Verma , S. Barnabe , R.D. Tyagi , J.R. Valero , R. Surampalli

    Organizations: a INRS-ETE, Universite du Quebec, 490, Rue de la Couronne, Que., Canada G1K 9A9 b Service Canadien des Forets, Centre de Foresterie des Laurentides, 1055 du P.E.P.S., P.O. Box 3800, Sainte-Foy, Que, Canada G1V 4C7 c US Environmental Protection Agency, P.O. Box 17-2141, Kansas City, KS 66117, USA

    The effect of a surface active agent, Tween 80 (0.2%, v/v) on production of Bacillus thuringiensis (Bt) based biopesticides using secondary wastewater sludge (non-hydrolysed (NH) and hydrolysed (TH)) as a raw material was studied in bioreactors. Hydrolysed sludge exhibited higher entomotoxicity (Tx) (49% increase) and cell/spore concentration vis-a-vis non-hydrolysed sludge. Amending the non-hydrolysed sludge with Tween 80 resulted in increase in cell and spore count by 1.67 and 4 times respectively, maximum specific growth rate (mmax) increased from 0.19 to 0.24 h-1 and Tx increased by 26.6%. However, addition of Tween 80 to hydrolysed sludge increased cell and spore count only by 2- and 2.4-folds, respectively and mmax increased from 0.28 to 0.3 h-1 with no change in Tx. Volumetric mass transfer coefficient varied significantly during fermentation and oxygen uptake rate (OUR) also increased 5 and 3.5 times for Tween 80 fortified nonhydrolysed and hydrolysed sludge, respectively. There were variations in viscosity during fermentation due to concerted effects of increase in viable cell and spores, cell lysis, agitation, aeration and anti-foam addition. The particle size decreased markedly in all cases at the end of fermentation.