Abstract
Mated cultures of Blakeslea trispora, grown in a potato extract-glucose-thiamine medium, produced 10 to 15 times more beta-carotene than either unmated culture. Mated, but not unmated, cultures produced a family of compounds (beta factor) which stimulated carotenogenesis in unmated cultures. In fact, carotenogenesis was stimulated sixfold more in minus cultures than in plus cultures. By altering the relative amounts of plus and minus inocula used in fermentations of mated cultures, it was possible to separate the synthesis of beta factor from the synthesis of extra beta-carotene. The plus strain appeared to produce the beta factor; the minus strain appeared to produce most of the extra beta-carotene. Kinetic studies of beta-factor formation suggested that physical contact between the two strains may be required to initiate beta-factor synthesis.