Development of a novel Escherichia coli assay for rapid and accurate quantification of lysine bioavailability

There is an increasing requirement from the food and feed industries for a more rapid and accurate approach to determine lysine bioavailability of protein sources. Lysine is an essential amino acid for humans and is often the first limiting amino acid in swine and poultry. Also, lysine is used as an indicator of protein quality. Consequently, assessing the bioavailability of lysine is critical to satisfy dietary requirements and for least cost formulation.; The overall objective of this research is to develop a rapid and accurate in vitro Escherichia coli assay for the determination of lysine bioavailability. This involved (1) characterizing the growth of an E. coli lysine auxotrophic mutant, (2) comparing two defined minimal media on growth of an E. coli lysine auxotroph and investigating the effect of inocula level as a potential means to reduce the total assay time, (3) determining the effect of soluble Maillard reaction products on the growth of E. coli strains, (4) cryopreserving lysine auxotroph culture, and (5) constructing a stable E. coli lysine auxotrophic mutant for the lysine assay. Completion of the objectives allowed for rapid determination of lysine bioavailability and potential replacement or reduction of utilizing animal assays.