Supplement C BD Difco™ 6 x 5 ml. This is a desiccated yeast concentrate used to supplement media for cultivating fastidious organismswith exact growth requirements. BD Difco™ Supplement C contains the thermolabileand thermostable growth accessory factors of fresh yeast, including glutamine, coenzyme (Vfactor), hematin (X factor), cocarboxylase, and other growth factors required for the growth offastidious organisms.