Lactic acid production during the associated and the deceleration growth phases of Lactobacillus helveticus cultivated in various conditions and media

Both growth phases, associated and deceleration, must be considered in the optimization of the lactic acid fermentation. The objective is to maximize the part of lactic acid produced during growth, firstly by a growth-associated mechanism and during the subsequent deceleration phase. Analysis of both growth phases has been carried out from the comparison of growth and lactic acid production rates by L. helveticus. The linked or the partially linked production during the growth-associated and the deceleration growth phases, respectively, increased when the culture conditions were close to the optimal ones; in this case, almost half of the final amount of lactic acid is produced during the short (2 h) deceleration growth phase. The part of lactic acid produced during growth, as well as the growth-associated coefficient A (corresponding to the product on biomass yield Y-P/X), are mainly controlled by the culture conditions (media composition, pH, lactate and undissociated lactic acid concentrations), but are not affected by seed culture conditions (media, length and inoculation level). High values of the growth and production rates resulting in a strong production during both growth phases, associated and deceleration, corresponded to low values of the product on biomass yield Y-P/X.