Induced Phase Separation and Recovery of 2,3-Butanediol from Fermentation Broth

2,3-Butanediol (2,3-BDO) is a promising platform chemical that can be utilized in a wide range of applications including pharmaceuticals or as a building block for sustainable aviation fuel (SAF). Presently, 2,3-BDO is produced using petroleum feedstocks, however, it can also be produced by bacterial fermentation of sugars. A major drawback to biobased 2,3-BDO production is the costly separation and recovery process. Due to the high boiling point of 2,3-BDO (177 °C), a traditional distillation process would be energy intensive. This work evaluated the separation and recovery of 2,3-BDO from fermentation broth produced using molasses. The Gram-positive bacterium strain Paenibacillus polymyxa was cultivated in molasses medium and generated 38.9 g/L of 2,3-BDO at a 1.5 L bioreactor scale. The fermentation broth was then subjected to induced phase separation for 2,3-BDO recovery using either NaCl or (NH₄)₂SO₄, and either ethanol (EtOH), ethyl acetate (EtAc), or a 1:1 blend. (NH₄)₂SO₄ in an equal volume mixture of EtOH/EtAc provided the maximum 2,3-BDO recovery yield (85.5%) from the fermentation broth followed by (NH₄)₂SO₄ in EtOH (75.5%). The highest 2,3-BDO recovery yield (73.4%) using NaCl was achieved with EtAc. Both recovery yields using (NH₄)₂SO₄ were achieved at only 20% (w/v of broth) inorganic salt loading, but the highest recovery yield using NaCl was achieved at a higher 60% (w/v of broth) loading. While the 2,3-BDO product titer generated during fermentation requires increasing for economical separation and recovery, the results highlight the promising aspect of using low chemical loadings (i.e., inorganic salts) for near-complete recovery of 2,3-BDO from fermentation broth.