> When 2,3-butanediol (2,3-BDO) is produced through microbial fermentation, common byproducts include ethanol, acetoin (acetylmethyl-carbinol), lactic acid, acetic acid, formic acid, succinic acid, CO2, and H2, depending on the microorganism and fermentation conditions, with acetoin and diacetyl being key intermediates in the pathway.

The intermediate diacetyl appears to have a potentially major side effect which, at scale, may make it a non-starter.

> Inhalation of vapors can cause bronchiolitis obliterans, a severe and irreversible lung disease, leading to coughing, wheezing, and shortness of breath, notes CDPH