Continuous ultrasonic-mediated solvent extraction of lactic acid from fermentation broths

A novel method of lactic acid recovery from fermentation broths by continuous ultrasonic solvent extraction is disclosed in this study. Fermentation broths from defined medium, mixed food waste hydrolysate and bakery waste hydrolysate were employed. Ultrasonication was applied to improve the extraction efficiency combined with ethyl acetate optimum solvent to replace conventional amine-based complex systems. The optimization process was performed by investigation of various conditions, in which initial lactic acid concentration range of 350–400 g L⁻¹ extracted into ethyl acetate (1:2 v/v) by sonication at pH 2 under room temperature was suggested. Lactic acid was successfully recovered with a concentration of 400–500 g L⁻¹, at overall yields of 82–84%, and purity around 98%, showing the high effectiveness of this new method. The simple and effective recycling of the solvent confirms the method in a green and sustainable manner.