A cyclic pathway for the bacterial dissimilation of 2, 3-butanediol, acetylmethylcarbinol, and diacetyl. I. General aspects of the 2, 3-butanediol cycle.

It is a well established fact that all organic compounds produced by living cells can be broken down by microorganisms. During the dissimilation of carbohydrates by organisms such as Aerobacter and certain members of the genus BaciUus 2,3-butanediol (2,3-butylene glycol) is formed as the chief product of the fermentation. There are many organisms in the soil that can use 2,3-butanediol or acetylmethylcarbinol (AMC, acetoin) as the sole source of carbon and energy for growth (Lemoigne et al., 1952; Sebek and Randles, 1952; Juni, 1952a). Studies in this laboratory have revealed a new pathway for the dissimilation of 2,3-butanediol by these organisms (Juni and Heym, 1953). Although the breakdown of 2,3-butanediol is an aerobic process, nearly all the reactions involving its oxidation to acetic acid can take place anaerobically as well as aerobically. The new pathway is a cyclic process involving two new intermediates, diacetylmethylcarbinol (DAMC) and acetylbutanediol (ABD). The cycle appears to be a method for generating acetic acid, a compound which these organisms oxidize readily. The present paper will be concerned with the general aspects of the reactions of this pathway.