Novel approach for large-scale, biocompatible, and low-cost fractionation of peptides in proteolytic digest of food protein based on the amphoteric nature of peptides

A large-scale, biocompatible, and low-cost procedure for peptide fractionat ion based on the amphoteric nature of peptide is developed. A sample cell ( 120 x 100 x 50 mm) with four joint tubes (17 mm i.d. and 20 mm in length) o n the front and back tvas prepared. On the end of the joint tubes, a nylon screen (100 mesh)-supported agarose gel layer was formed. Five or nine of t he sample cells were connected. A tryptic digest of casein (2.0-3.6 L) was applied to the sample cells. At each end of the sample cell apparatus, an a dditional cell filled with 0.1 M H3PO4 or NaOH was connected and used as an ode and cathode compartments, respectively. Reproducible fractionation of p eptide could be achieved by collecting fractions with specific pH values wh en voltage reached a plateau by applying direct current at constant power. Running time necessary for fractionation of peptide was inversely proportio nal to electric power and directly proportional to sample volume.