Nanofiltration and reverse osmosis membranes for purification and concentration of a 2,3-butanediol producing gas fermentation broth

• NF and RO membrane series identified for 2,3-butanediol fermentation separation.
• 2,3-butanediol and acetate successfully concentrated within a fermentation mixture.
• BW30 exhibits high rejection (93 %) of 2,3‑butanediol and acetate at pH 6.5.
• BW30 screening gave high rejections of isobutanol, tert-butanol and 1,3-butanediol.

For sustainably produced fuels and chemicals to become viable resources they need to be cost comparable with crude oil based products. 2,3-Butanediol is an important commodity chemical that can be produced via gas fermentation alongside acetate and ethanol. The current recovery of 2,3-butanediol is an energy intensive process to which membranes could be incorporated, to achieve energy and monetary savings through partial purification and/or concentration of the desired products. This paper investigates for the first time a number of nanofiltration and reverse osmosis membranes for this purpose. Three membranes (NF270, NF90 and BW30) were investigated for their applicability to concentrate 2,3-butanediol, acetate and ethanol within a gas fermentation broth. BW30 was identified as a suitable membrane for the concentration of 2,3-butanediol and acetate within the gas fermentation broth with rejections of 96.1% and 94.6% respectively at pH 6.5. Rejection of other possible alcoholic fermentation products was also screened with BW30 for the concentration of these products.Overall, this work demonstrates how NF and RO membranes could be implemented within a membrane series to potentially replace part of the distillative separation of low volatility organics from fermentations.

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