Formulation of spore toxin complex of Bacillus thuringiensis and Lysinibacillus sphaericus grown under solid state fermentation

Abstract

Formulation of whole solid-state fermentation (SSF) products of Bacillus thuringiensis israelensis (Bti) and Lysinibacillus sphaericus (Ls14N1) and their extracts was studied. Results of formulation of final SSF products showed that drying at 40 °C was one of the most efficient methods for formulation of both tested cultures with preserving complete mosquitocidal activities for at least 8 months. Ls14N1 final whole SSF product was efficiently formulated by addition of propionic acid at 0.3% or acetic acid at 0.3% and was completely active against Culex pipiens larvae after 8 months storage at room temperature. Also, addition of ascorbic acid 0.05%, sodium benzoate 0.3%, citric acid 0.2% or sodium chloride 10% were promising preservatives for Ls14N1 SSF product. However, Bti SSF product was formulated by addition of 25–70% sugar and completely preserved active for 4 months. On the other hand, formulation of liquid extracts of SSF product was studied to have liquid and powder preparations. The best preservatives for spore toxin complex (STC) liquid extract of Ls14N1were calcium chloride 20–40%, sodium benzoate 3–6%, sodium chloride 10–100%, potassium sorbate 2% or acetic acid 1%. Also, STC liquid extract of Ls14N1 was efficiently formulated in solid form by addition of Chipsy starch, wheat flour or wheat germ meal as carriers. Those formulations were nearly mosquitocidal active after 10 months storage. For formulation of Bti liquid extract, sodium benzoate 3–6% or sodium chloride 10–20% were the best preservatives. On the other hand, Chipsy starch and wheat flour were the most promising carriers for preparation of solid formulation. All these Bti formulations were completely active for 8 months. This study may contain simple, cost effective and efficient methods for preparation of mosquitocidal formulations of Ls and Bti mosquitocidal toxins produced under SSF technology.