ABSTRACT
Bacillus thuringiensis (Bt) can use a variety of carbon sources: glucose, fructose, maltose, ribose, sucrose, lactose, starch, whey, soybean oil, glycerol, organic acids and amino acids. The different Bacillus thuringiensis varieties produce a wide range of Cry insecticidal proteins, which exemplifies the progressive adaptation of the microbe to the ecological niche constituted by insects. The bacteria have developed several strategies to massively overproduce the endotoxins: for example, multiple copies of cry genes, strong promoters, extended half-life mRNAs and the crystallization process to resist proteases. Medium composition and process conditions should direct all of those phenomena to the overproduction of Cry and good cell growth. Bt research is primarily focused on its molecular biology, genetics and isolation of new strains. Bt have been produced using two fundamental technologies: semisolid and submerged fermentations. At the laboratory and pilot plant scales, three alternatives have been studied for submerged Bt production: extended-batch, fed-batch and continuous culture.
