Penicillin production in liquid submerged cultures of the strains shown to produce an antibacterial compound that was inactivated by β-lactamase (see Table 1 and text). Strains depicted here are P. nalgiovense 16a (⧫), P. nalgiovense INBCC103 (commercial starter culture) (▪), P. chrysogenum AK (▴), P. griseofulvum NRRL 991 (□), P. griseofulvum NRRL 2152 (-), P. griseofulvum NRRL 994 (○), P. griseofulvum NRRL 992 (×), P. griseofulvum NRRL 989 (□), and P. griseofulvum NRRL 2300 (◊). Error bars, standard deviations.