The butanediols (BDOs), 2,3-, 1,4- and 1,3-butanediol, are platform chemicals that are mainly produced from fossil hydrocarbons but may be obtained through fermentation. However, low product concentration, by-product formation and high boiling temperatures of BDOs hinder downstream processing and increase overall fermentation costs. This study increases the competitiveness of industrial biotechnology by designing a large-scale process (broth processing capacity of 160 ktonne/y) for the final purification of BDOs after fermentation (recovery >99 %). It includes an initial preconcentration step in a vacuum distillation column to remove most water and light impurities. The initial removal of most of the water and the use of a heat pump system allowed significant energy reduction. At the heart of the process is an integrated dividing-wall column that can efficiently purify BDO from the remaining light and heavy impurities. Moreover, a single process design was proven effective in purifying different BDOs to > 99.4 wt%. This was cost-effective (total purification costs of 0.208 – 0.243 $/kgBDO) and energy-efficient (with primary energy requirements of 1.854 – 2.176 kWthh/kgBDO). The proposed purification sequence can be used for each BDO type, which offers flexibility in developing sustainable bioprocesses for BDO production.

Fermentation can be used to obtain a wide variety of valuable high-boiling components. Among these components, microorganisms can produce aliphatic diols (e.g. propanediols, butanediols, etc.) in significant concentrations (e.g. 5–15 wt.%). Nonetheless, the high boiling points of these components, presence of microorganisms, and formation of by-products complicate recovery after fermentation. Hence, this perspective offers valuable insights into downstream processing options. A novel methodology was developed for recovering high-boiling components from dilute aqueous solutions, whereby both light and heavy impurities are present. The main steps in the proposed methodology are heat pump-assisted preconcentration and final purification in a dividing-wall column. These steps allow effective separation of high-purity product from water, light and heavy impurities. Furthermore, processes for recovery of 1,3-propanediol, 2,3-, 1,4- and 1,3-butanediol, designed according to the proposed methodology, were compared. Downstream processing performance is mainly determined by the product concentration in the fermentation broth, but is also influenced by the amount of impurities in the broth.