The aim of this work was the determination of the best experimental conditions for the production of amino acids from bovine serum albumin (BSA) by continuous sub-critical water hydrolysis. The results were compared with conventional acid hydrolysis in HCl. At a residence time of 30 s and a pressure of 25 MPa, the highest amount of amino acids was obtained at 5 83 K. An increase in residence time to 90 s led to a shift of the temperature optimum to 543 K. The highest amino acid yield in sub-critical water was obtained at 563 K and 65 s. No significant influence of operating pressure (15-27 MPa) could be observed at the tested temperature (523 K) and residence time (30 s). The addition of carbon dioxide led to an increase in amino acid yield due to the acceleration of acid hydrolyzed catalysis steps. This protein treatment may provide a practical and economical solution for the disposal of protein-rich sources like marine wastes, hairs, and feathers, which are considered as waste so far. (c) 2005 Elsevier B.V. All rights reserved.