Quantitative determination of ?-endotoxin contents in spray-dried preparations ofBacillus thuringiensis strain GC-91

Abstract

This report describes a method for quantifying δ-endotoxin contents in spray-dried preparations ofBacillus thuringiensis strain GC-91. δ-Endotoxin is solubilized in the pro-toxin form and separated from other soluble compounds by ion exchange chromatography. The method does not discriminate between the different δ-endotoxins produced by strain GC-91. It is suitable for quality control, since δ-endotoxin concentrations found in different preparations correlate inversely with the LC 50 in bioassays on artificial diet against freshly hatched larvae ofSpodoptera littoralis. A typical batch of spray-dried material contains 1.22%±0.08% δ-endotoxin. The method is most accurate with preparations containing 0.5 to 2.0% toxin, for which triplicate estimations give standard errors close to±0.2%.

Importance of Cry Proteins in Biotechnology: Initially a Bioinsecticide, Now a Vaccine Adjuvant

“…Bt is a Gram-positive, catalase-positive, oxidase-negative, strictly aerobic bacterium with peritrichous flagella that enable motility. It is generally found in soils, but it is also present in water, insects, some grains, and the environment [11,[22][23][24][25]. Bt has two life cycles: vegetative growth and a sporulation phase.…”