STABILIZATION AND INCREASED PRODUCTION OF INSECTICIDAL CRYSTAL PROTEINS OF BACILLUS-THURINGIENSIS SUBSP GALLERIAE IN STEADY-STATE AND TRANSIENT-STATE CONTINUOUS CULTURES

Bacillus thuringiensis subsp. galleriae, grown in continuous cultures, segregated to spontaneous asporogenic variants replacing the wild-typ e Spo(+) Cry(+) strains [Sachidanandham R, Jayaraman R (1993) Appl Mic robiol Biotechnol 40:504-507]. Realizing that this was due to specific but unknown nutritional requirements, we undertook further continuous -culture studies to identify growth requirement(s) by pulsing various medium components and growth factors. While carbon, nitrogen and pulse s of nutrients exhibited a neutral pulse response, a group of amino ac ids were shown to improve the stability and volumetric productivity of biomass. The formation of spores and insecticidal crystal proteins wa s found to be higher with amino acid supplementation. Comparison of ca rbon-limited steady-state continuous cultures under two different cond itions of growth brought forth the stabilizing effects of the amino ac id supplementation. Batch experiments carried out with these inputs de monstrated a better carbon utilization, resulting in a higher biomass as well as enhancement of bioinsecticidal activity.