[Influence of various ions in sporulation and the formation of delta-endotoxin in Bacillus thuringiensis cultures].

This paper deals with studies related to the influence of several ions on growth, spore formation and endotoxin formation by a Bacillus thuringiensis HD-1 strain commonly used for bioinsecticide production. Two basal media (4 and 5, Table 1) containing glucose, (NH4)2 SO4, phosphates and yeast extract or bacto peptone as organic nitrogen sources were supplemented with several ions in different concentrations, as shown in table 1. The experiments were conducted in 1000 ml Erlenmeyer flasks, containing 100 ml of medium, located in a rotary shaker at 30 degrees C. Several estimations were carried out, mainly biomass by optical density and colony forming units (CFU), glucose, Mg+2 and Mn+2 consumption and delta-endotoxin by a rocket immunoelectrophoretic method. The results obtained (Table 2) clearly show the importance of the addition of Ca+2, Mg+2 and Mn+2 to the basal media, because the highest values of CFU/l and delta-endotoxin (expressed as protein in g/l) were achieved in those media supplemented with the ions mentioned. It was also proved that the supplementation with Ca+2 was also essential for maintaining the thermal stability of the spores (Table 3). It can be concluded that an adequate formulation of media mainly related with the content of Mn+2, Mg+2 and Ca+2 is essential for obtaining high yields of spore crystal production of a Bacillus thuringiensis HD-1 strain.