Final answer:
Casein, a protein found in milk, can be isolated and identified using techniques such as isoelectric focusing, high-pressure liquid chromatography (HPLC), and mass spectrometry.
Step-by-step explanation:
Casein is a protein found in milk. Isolation and identification of casein can be done using several techniques. One method is isoelectric focusing, where the pH is adjusted to the isoelectric pH of casein, causing it to precipitate. Another method is high-pressure liquid chromatography (HPLC), where the proteins are separated and then digested into smaller peptide fragments. Mass spectrometry is used to identify these peptide fragments and compare them with known microorganisms to identify the unknown protein.