Continuous production of lactic acid from whey permeate by Lactobacillus helveticus in two chemostats in series

The effect of diln. rate on the prodn. of lactic acid from whey permeate by L. helveticus was investigated. In the 1st chemostat of a 2-stage system, total conversion (98.1%) and max. lactic acid concn. (43.7 g/L) were obtained at a diln. rate (D1tot) of 0.06/h. Max. volumetric productivities of lactic acid (8.27 g/L-h) and biomass (1.90 g/L-h) occurred at D1tot of 0.40/h. The fraction of L-lactate in the product increased with diln. rate and reached a max. of 66% at the same diln. rate. The max. sp. growth rate (mmax) on this medium was 0.7/h. A YATP(max) value of 22.4 g dry wt./mol ATP and a maintenance coeff. of 8.0 mmol ATP/g dry wt.-h were detd. The 2nd stage, in series with the 1st, confirmed these results and also showed that the total residence time could be reduced by 50% compared with a single chemostat for the same nearly complete level of substrate conversion. [on SciFinder (R)]