Optimization of culture conditions for high-level expression of dextransucrase in Escherichia coli

The use of lactose as inducer for the expression of dextransucrase was investigated in high density of Escherichia coli. Different culture conditions including carbon source, nitrogen sources, inorganic salts, inoculum density (OD 600 ) and lactose concentrations were optimized, and high-level expression of dextransucrase in E. coli was achieved via an optimal culture conditions. The results indicated that glycerol and tryptone were suitable carbon source and nitrogen source for dextransucrase expression respectively; organic nitrogen sources were found to enhance the enzyme production. Optimal conditions were added lactose of 5 g l when OD 600 reached 3.0 and cultivation continued at 25°C for 7 h. Maximal activity under these conditions was 60.18 U/ml.