Influence of dilution rate on the morphology and technological properties of Lactobacillus delbrueckii subsp. bulgaricus
1994
Ragout, A. | Sineriz, F.
Lactobacillus delbrueckii subsp. bulgaricus ATCC 11842 was grown in a chemostat at 45 degrees C and pH 5.5 using glucose as the carbon source, with the aim of optimizing biomass production. Cells were grown in a complex medium under nitrogen. At dilution rates lower than 0.18 h(-1), it was difficult to keep steady-state conditions and pleomorphic forms were observed. The addition of 30 mM Ca(2+) and Mn(2+) reverted the cells to normal shape: 3O mM Mg(2+) had no effect. Increasing the dilution rate resulted in normal morphology without the addition of any cations. Under these conditions, a maximum productivity of 1.24 g dry biomass l(-1) h(-1) was obtained. The maximum growth yield, corrected for maintenance, was 30 g biomass mol(-1) glucose and the maintenance energy was 0.26 g glucose g(-1) biomass h(-1). Lactate was the main fermentation product at all glucose concentrations used in the feed medium. Cells grown at high dilution rates had normal technological properties (acid production and proteolysis) when tested in milk.
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