A membrane filtration separation process used to separate fine particles and molecules. The membrane consists of a polymeric microporous material with a pore size of between 0.1 and 10 micrometres. The filtration separation uses an applied pressure across the membrane as the driving force. It is typically used for the separation of proteins from yeast cells following the process of fermentation, clarification of liquid beverages, separating cream from whey in milk, and the sterilization of liquids by filtering out microorganisms.