The effect of #alpha#-lactalbumin and #beta#-lactoglobulin hydrolysates on the metabolic activity of Escherichia coli JM103

摘要

Bovine milk proteins #alpha#-lactalbumin (#alpha#-la) and #beta#-lactoglobulin (#beta#-lg) were hydrolysed with seven different proteolytic enzymes, and the effect of various hydrolysates on a genetically modified luminous Escherichia coli JM103 was tested in vitro with a bioluminescence assay for bacterial growth and metabolism. Undigested proteins did not inhibit the activity of tested E. coli JM103 at a concentration as high as 0.1 g ml~(-1). At the same concentrations, #alpha#-la hydrolysed with pepsin or trypsin and #beta#-lg hydrolysed with alcalase, pepsin or trysin, showed a lower metabolic activity during the first 8 h of growth. The activity of E. coli JM103 in the presence of 25 mg ml~(-1) #alpha#-la or #beta#-lg hydrolysed with pepsin and trypsin was only 21% of the control after incubation for 6 h. The preliminary results indicated that ultrafiltration through 10 kDa and 1 kDa molecular mass cut-off membranes may be used to enrich bacteriostatic properties.