FIG. 4.

Analysis of optical purity of l-lactate in fermentation broth using a chiral column. Absorbance is plotted relative to retention times (in minutes). Retention times are also noted above peaks. (A) Standards: a mixture of 10 mM l-(+)-lactic acid and 10 mM d-(−)-lactic acid. (B) Broth from SZ85. This broth contained 500 mM l-(+)-lactic acid and was diluted 40-fold prior to analysis on the chiral column. d-(−)-Lactic acid was estimated from the peak area at 12.02 min. (C) Diluted broth from SZ85 to which 0.05 mM d-(−)-lactic acid was added as an internal standard. Purity of the l-(+)-lactic acid from SZ85 was estimated to exceed 99.5%.