Recovery of organic acids from lactic acid-enriched fermentation broth via salting-out assisted solvent extraction

The organic acids (OAs) market has been expanding due to their versatility and wide range of uses in several industrial applications, thus prompting a transition from chemical to biological approaches to generate such high-value products. Nevertheless, downstream processes to separate OAs from the fermentation broth represent, to date, the main cost in biological OAs manufacturing. With the goal of limiting this issue, the present study investigated OAs separation from a lactic acid (LA)-rich fermentation broth through physical, i.e., using ethyl acetate (EA), and physico-chemical, i.e., using tributyl phosphate (TBP), solvent extraction. In addition, the salting-out effect of different salts on OAs recovery was investigated. Among the investigated conditions, a combination of pure TBP and 40% ammonium sulfate ensured the highest LA extraction efficiency of 65%. Besides, mixing TBP with EA (50:50) enabled to maintain the same LA extraction efficiency while reducing the process costs, limiting the toxicity of the chemicals involved, and obtaining an extracted OAs mix with lower co-metabolites, i.e. volatile fatty acids, compared to using pure TBP. Overall, solvent extraction assisted by salting-out agents were shown to be a promising method to separate OAs from a fermentation broth in liquid form, especially for fermentation processes operated at low pH.