 Base Ingredients of Microbiology Media by Merck

Primary source: www.merckmillipore.com/AG/en/technical-documents/technical-article/microbiological-testing/microbial-culture-media-preparation/base-ingredients-of-microbiology-media

Verified locator: Proteins (Protein Hydrolysate, Amino Acids, etc.): peptones as protein hydrolysates made by enzymatic digestion or acid hydrolysis from natural sources.