The production of 2,3-butanediol by fermentation of high test molasses

Summary

Klebsiella oxytoca fermented 199 g·l⁻¹ high test or invert molasses using batch fermentation with substrate shift to produce 95.2–98.6 g 2,3-butanediol·l⁻¹ and 2,4–4.3 g acetoin·l⁻¹ with a diol yield of 96–100% of the theoretical value and a diol productivity of 1.0–1.1 g·l⁻¹·h⁻¹. Fermentation was performed numerous times with molasses in repeated batch culture with cell recovery. Such repeated batch fermentation, in addition to a high product yield, also showed a very high product concentration. For example, 118 g 2,3-butanediol·l⁻¹ and 2.3 g acetoin·l⁻¹ were produced from 280 g·l⁻¹ of high test molasses. The diol productivity in this fermentation amounted to 2.4 g·l⁻¹·h⁻¹ and can undoubtedly be further increased by increasing the cell concentration. Because the Klebsiella cultures ferment 2,3-butanediol at an extremely high rate once the sugar has been consumed, the culture was inhibited completely by the addition of 15 g ethanol·l⁻¹ and switching off aeration.