Isolation of Some Minor Milk Proteins, Distributed in Acid Whey from Approximately 100,000 to 250,000 Daltons of Particle Size

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Abstract
Milk proteins in acid whey were separated into five fractions according to molecular size by gel filtration chromatography. The second peak, P2, contained proteins between approximately 250,000 and 100,000 daltons. Proteins in P2 were concentrated. After separation into albumins and globulins, each protein group was isolated by DEAE chromatography and hydrophobic interaction chromatography. Isolated albumin fractions were a yellow-colored protein of 89,000 daltons, an unidentified protein of 73,000 daltons, a .beta.-lactoglobulin of 18,3000 daltons, and a red-colored protein of 87,000 daltons. Two types of globulin fractions were isolated: 1) a globulin fraction that coagulated in saturated sodium sulfate but did not coagulate when dialyzed against deionized water included a brown-colored protein of 150,000 daltons, and 2) a bovine serum albumin of 67,000 daltons with unidentified 170,000 and 30,000 daltons bands. A true globulin fraction contained a 77,000 dalton unidentified protein with several faint bands. The red-colored protein was identified as lactoferrin and the brown-colored protein as xanthine oxidase (EC 1.2.3.2.). A yellow-collored protein was concluded to be the denatured protein of contaminated lactoperoxidase (EC 1.11.1.7).