What corn-industry byproduct increased penicillin yield tenfold in Moyer and Heatley's work?

Corn steep liquor was the corn-industry byproduct that increased penicillin yield tenfold in Moyer and Heatley’s work.

Andrew J. Moyer encountered it at the U.S. Department of Agriculture’s Northern Regional Research Laboratory in Peoria, Illinois, where researchers routinely tested corn-processing byproducts for useful fermentation applications. Corn steep liquor is the nutrient-rich liquid left from corn wet-milling; it contains organic nitrogen, amino acids, peptides, vitamins, and minerals.

Moyer added it to the mould’s growth medium while Norman Heatley helped evaluate the resulting production process. The improvement was dramatic: the medium’s penicillin yield rose tenfold, helping turn laboratory-scale production into a practical industrial process. Moyer also replaced sucrose with lactose, another important improvement.

A common mix-up is confusing corn steep liquor with molasses. Molasses was important in some fermentation industries, but corn steep liquor was the specific byproduct associated with this penicillin breakthrough. Its role was nutritional, supporting the mould and its production of penicillin rather than acting as the antibiotic itself.