Recovery of acetoin from Bacillus subtilis fermentation broth by supercritical CO2 extraction

Component enrichment from fermentation broths by solvent extraction using supercritical carbon dioxide (sCO(2)) has been demonstrated in the literature. This work investigates for the first time the feasibility of the enrichment of an acetoin fraction from a real fermentation broth at a pilot plant scale using sCO(2). A 4-m-tall, 28-mm-diameter, counter-current column packed with pall rings was used. The ranges of process pressure and temperature investigated were 100 to 300 bar, and 37 to 80 degrees C respectively. The optimum recovery of acetoin was 77.8%, with little difference between the simulated and actual broths. A modest two-fold concentration of acetoin was obtained in the extract. The results show that where a modest enrichment of the targeted product makes a significant difference in subsequent separation processes, and where the purity of the product, particularly from harmful solvents, is important, sCO(2) fluid separation is a credible option for the enrichment of such products of fermentation.