2,3-butanediol fermentation produces smaller amounts of acid than mixed acid fermentation, and butanediol, ethanol, CO and H are the end products. While equal amounts of CO and H are created during mixed acid fermentation, butanediol fermentation produces more than twice the amount of CO because the gases are not produced only by formate hydrogen lyase as they are in mixed acid fermentation.
2,3 Butanediol is produced at varying levels in aerated fermentations as long as the dissolved oxygen level is limiting (i.e., the culture is trying to consume more oxygen than is available). The degree of oxygen limitation dictates the ratios of 2,3-butanediol to by-products produced.