Specificity of Escherichia coli lysine auxotroph growth kinetics and lysine assay response to various soluble Maillard reaction products
2002
Li, Xunjing | Ricke, S.C.
Lysine availability in foods or feeds can be rapidly assessed by an Escherichia coli lysine auxotroph (lys(-)) based assay. The overall objective of these studies was to examine if the accuracy of this lysine assay was affected by the presence of different soluble Maillard reaction products (MRP) in a model system. The standard curve without addition of MRP was parallel to the standard curves with addition of histidine-MRP (histidine with glucose) or arginine-MRP (arginine with glucose). The y-axis intercept of the standard curve without addition of MRP was significantly (P < 0.05) greater than the y-axis intercepts of the standard curves with addition of MRP. This data indicated that MRP inhibited lys(-) growth when limited by lysine concentration, and accurate determination of lysine availability in food or feed sample may require an internal standard curve where known lysine increments are added to the samples to be analyzed.
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