corynebacterium glutamicum with a d lactate dehydrogenase activity of 0 05 8 u mg can be used particularly suitable are mutants of corynebacterium glutamicum atcc 13032 and atcc 14310 which were obtained by the known treatment of the last named strains with n methyl n 39 nitro n nitrosoguanidine and are deposited with the german strain collection for microorganisms in gottingen under the numbers dsm 3717 and 3718 they grow on the nutrient medium containing d lactate and contain a d lactate dehydrogenase activity of approximately 0 25 or 0 4 u mg while the initial strains contain only approximately 0 1 u mg the activity was determined in accordance with the procedure described in 34 microbiological reviews 34 44 1980 pp 106 to 139 mutants with a d lactate dehydrogenase activity of gt 0 1 to 1 5 u mg are suitable for the method of the invention the fermentation of the isolated mutants of corynebacterium glutamicum is performed in shake cultures or in fermenters under aerobic conditions at a reaction temperature of 20 u00b0 45 u00b0 c and a ph of 5 9 calcium carbonates and ammonium salts are suitable for the correction of the ph the fermentation medium contains a carbon source d l u03b1 hydroxybutyric acid a nitrogen source and other elements suitable carbon sources for the fermentation are sugar protein hydrolysates and proteins d l u03b1 hydroxybutyrate can be added to the reaction batch as a free acid or as a salt such as e g sodium salt or calcium salt in a concentration of 0 01 50 g l it is preferable if the concentration of the initial compound does not exceed 20 to.