Virginiamycin is a streptogramin, and a mixture of Virginiamycin M1 and Virginiamycin S1. The commercial mixture is 75 % Virginiamycin M1 and 25 % Virginiamycin S1, along with less abundant S analogs. The mixture can be used to reduce contaminating bacteria during yeast fermentation for bioethanol production. Virginiamycin is soluble in DMSO and DMF.