Implementation of forward osmosis to concentrate alpha-ketoglutaric acid from fermentation broth: Performance and fouling analysis

Abstract

Forward osmosis (FO) was demonstrated as a promising method to concentrate alpha-ketoglutaric acid in fermentation broth. Using a model solution containing alpha-ketoglutaric acid, the impact of the initial pH value on water flux, reverse salt flux, and rejection of alpha-ketoglutaric acid were first elucidated. Results from this study show that water flux was not affected by feed solution pH. However, feed solution pH could influence alpha-ketoglutaric acid rejection and reverse salt flux. The highest alpha-ketoglutaric acid rejection of 99.7% and lowest reverse salt flux were observed at pH 5. Multi-component model and real fermentation broth were then used to validate FO application for concentrating alpha-ketoglutaric acid. Water recovery of 80% was achieved without severe membrane fouling. In addition, membrane fouling analysis show that the built-up fouling layer of impurities is flaky and of unstable nature, suggesting that membrane fouling could be reversible. Knowledge of the fouling layer formation can contribute to the development of an effective method of pretreatment of the fermentation broth and cleaning FO membranes in the future.