The separation of racemic tryptophan and its analogs can be performed by ultrafiltration in a solution system using bovine serum albumin (BSA) as a complexing agent. Three models have been tested to simulate the complexation mechanism of tryptophan and kynurenine enantiomers to BSA protein. In the pH range from 7 to 11, the most probable complexation mechanism was a competitive binding of D- and L-enantiomers on a single site. Based on these results the enantiomeric separation of these amino acids can be optimized in order to improve the selectivity and recovery of the BSA solution process.