In early 1954, Demain moved to Danville, Pennsylvania, where he worked as a research microbiologist for Merck Sharp & Dohme, studying the synthesis of penicillin. His work helped identify the amino acids that form the nucleus of penicillin, established the mechanisms that enable primary metabolites and carbon sources to regulate secondary metabolite synthesis, and demonstrated that penicillin was the product of synthesis and inactivation during fermentation. In late 1955, Demain moved on to Merck's penicillin research laboratories in Rahway, New Jersey, where he worked on fermentation microbiology, â-lactam antibiotics, flavor nucleotides, and microbial nutrition.
