Effect of saccharides on growth, sporulation rate and δ-endotoxin synthesis of Bacillus thuringiensis

cfu/ml). However, the presence of appropriate quantity of glucose was required to trigger -endotoxin formation. The presence of -endotoxin with molecular weight of 130 kD assayed using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), was only detected after 48 h of cultivation using 8 g/L glucose as the sole carbon source. Although good growth with high spore production was obtained in cultivation using a mixture of glucose (4 g/L) with other sugars, the spores produced contained no endotoxin. The existence of -endotoxin was also observed in cultivation using a mixture of various sugars (fructose, sucrose, maltose and lactose) with 8 g/L glucose, indicating that high glucose (> 8 g/L) must be present in the culture to trigger -endotoxin formation in the spores of Bacillus thuringiensis MPK13.