Patent ID: 7049108

Claim:
A process for the preparation of lactic acid, comprising: growing, in a fermentation medium containing a carbon source, a yeast strain transformed with at least one copy of a gene coding for lactate dehydrogenase functionally linked to a promoter sequence allowing the expression of the gene in the yeast stain, wherein the yeast strain produces lactic acid at a yield from 0.5 gram lactic acid per gram glucose to 0.881 gram lactic acid per gram glucose, and wherein the transformed yeast strain has undergone deletion of one or more pyruvate decarboxylase genes or pyruvate dehydrogenase genes, to produce lactic acid, wherein the yeast strain can grow or maintain its population at the pH of the fermentation medium, wherein the initial pH of the fermentation medium is higher than 4.5; and, recovering the lactic acid from the fermentation medium.