Production of lactic acid by continuous fermentation using an inexpensive raw material and a simplified method of lactic acid purification

Claim 1

A process for producing lactic acid from a carbohydrate-containing medium comprising the steps of: (a) fermenting said carbohydrate-containing medium with a lactic acid or lactic acid salt-producing microorganism in a fermentation ot form a broth; (b) continuously removing a product-containing both from said zone, removing cells of said microorganism from said broth to form a cell-free product-containing stream and recycling said cells to said zone; (c) contacting said cell-free product-containing stream at an acidic pH with a water-immiscible liquid consisting essentially of trialkyl tertiary amines of at least 24 carbon atoms and a water-immiscible organic solvent for a period of time and at a temperature sufficient to extract lactic acid and lactic acid salt from said stream into a water-immiscible phase, said liquid characterized by a distribution coefficient in excess of 1.0 for lactic acid and lactic acid salt in said liquid versus water; (d) separating said water-immiscible phase from the mixture formed in step (c); (e) contacting said water-immiscible liquid from step (d) with a material selected from the group consisting of aqueous ammonium hydroxide, solid alkalis, solid alkaline earth compounds, and aqueous non-homogenous suspensions of solid alkalis or solid alkaline earth compounds, whereby lactic acid and lactic acid salt are removed from said water-immiscible phase.