Butanol fermentation is also called ABE fermentation because of the co-production of acetone: butanol: ethanol during the fermentation process.
The butanol producing bacteria are from the Clostridium genus and are obligate anaerobes. The well-known industrial strains are C. acetobutylicum, C. saccharoperbutylicum, and C.beijerinckii.
In recent years, several other Clostridial strains have been reported for butanol production, most importantly without acetone production. This is a key advancement since, unlike ethanol and butanol,
acetone do not have fuel properties and hence should be removed completely at signifiant down-stream processing expense.
Traditional butanol fermentation has focused on sugary (sucrose) and starchy materials but the focus has recently shifted towards hydrolysates from lignocellulosic biomass.
However, butanol fermentation is one of the difficult fermentation pathways due to substrate and product inhibition. This can be avoided by fed-batch fermentation and in situ stripping of butanol.
Also, reducing the feedstock and enzyme costs will make the process more
economically viable. Through using industrial waste streams (negative costs), enzymatic cocktails tailored for the feedstock (allowing low-enzyme dosages), and
with high sugar yields, the right choice of microbial strain, and an effective in-situ removal technology, it is possible to develop an economically-viable butanol process.