Growth and lactic acid production coupling for Lactobacillus helveticus cultivated on supplemented whey: Influence of peptidic nitrogen deficiency

For Lactobacillus helveticus growing on supplemented whey permeate, some simple criteria have been proposed for assessing carbon and nitrogen source limitations: irrespective of supplementation, carbon limitation coincided with the end of lactic acid production. carbon limitation in absence of nitrogen deficiency led to an abrupt cessation of growth. nitrogen deficiency in the absence of carbon limitation resulted in an increase of the overall product on biomass yield Y-P/X during the second half of the cultivation. At pH near to the optimum (pH = 6), even al the end of reaction, the final concentration of free lactic acid was below the inhibitory threshold (0.45-0.60 g l(-1)). In these conditions the shift from total to partial growth-associated production was tightly controlled by the concentration of available peptidic nitrogen. (C) 1997 Elsevier Science B.V.