Extracellular lysine production by various fungi.

Cultures of over 600 fungi were screened for the production of extracellular free lysine in submerged agitated culture on a medium containing urea, cerelose, and mineral salts. Sixty-three of the isolates produced free lysine in quantities sufficient to be detected by a turbidimetric bio-assay procedure, and 12 of these produced 5-15 γ lysine per milliliter of culture nitrate. With two strains of Ustilago, yields were increased to 200–300 γ lysine per milliliter culture mixture by adjustment of cultural conditions. The addition of ammonium acetate or of acetic acid, or the increasing of the amount of urea in the medium from 0.06% to 0.6%, resulted in increased yields from certain organisms.