METHOD FOR PRODUCING LACTIC ACID

摘要

A method for producing lactic acid, comprising producing lactic acid from a sugar-containing fermentation liquid in a fermentor by means of lactic acid-forming bacteria to result in a lactate salt, typically ammonium, sodium or potassium lactate, and isolating lactic acid by subjecting the fermented fermentation liquid to a first ultrafiltration step to result in a substantially polymer-free permeate comprising at least one lactate salt, acidifying the permeate to a pH value of below about 3.9, performing at least one additional isolation step in which the acidified permeate is subjected to nanofiltration and/or reverse osmosis, and preferably subjecting the resulting product to electrodialysis using bipolar electrodialysis membranes. Fermentation is preferably performed using whey protein as a nutrient substrate and by adding at least one protein-hydrolysing enzyme directly to the fermentor during the fermentation process so that hydrolysis of protein to amino acids takes place simultaneously with the fermentation of sugar into organic acid.