n 1  :  any of various protein derivatives that are formed by the partial hydrolysis of proteins (as by enzymes of the gastric and pancreatic juices or by acids or alkalies), that are not coagulated by heat, and that are soluble in water but unlike proteoses are not precipitated from solution by saturation with ammonium sulfate  2  :  a complex water-soluble product that contains peptones and other protein derivatives, is obtained by digesting protein (as meat) with an enzyme (as pepsin or trypsin), and is used chiefly in nutrient media in bacteriology .
 
 
 
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