The critical role of urease in yogurt fermentation with various combinations of <em>streptococcus thermophilus and lactobacillus delbrueckii ssp. bulgaricus</em> - INRAE - Institut national de recherche pour l’agriculture, l’alimentation et l’environnement Access content directly
Journal Articles Journal of Dairy Science Year : 2019

The critical role of urease in yogurt fermentation with various combinations of streptococcus thermophilus and lactobacillus delbrueckii ssp. bulgaricus

R. Yamauchi
  • Function : Correspondent author
H. Horiuchi
  • Function : Author
M. Hosokawa
  • Function : Author
Y. Sasaki
  • Function : Author

Abstract

The protocooperation between Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus relies on metabolite exchanges that accelerate acidification during yogurt fermentation. Conflicting results have been obtained in terms of the effect of the Strep. thermophilus urease and the NH3 and CO2 that it generates on the rate of acidification in yogurt fermentation. It is difficult to perform a systematic study of the effects of urease on protocooperation because it is necessary to distinguish among the direct, indirect, and strain-specific effects resulting from the combination of the strains of both species. To evaluate the direct effects of urease on protocooperation, we generated 3 urease-deficient mutants (Delta ureC) of fast- and slow-acidifying Strep. thermophilus strains and observed the effects of NH3 or CO2 supplementation on acidification by the Delta ureC strains. Further, we examined 5 combinations of 3 urease-deficient Delta ureC strains with 2 CO2-responsive or CO2 -unresponsive strains of L. bulgaricus. Urease deficiency induced a shortage of ammonia nitrogen and CO2 for the fast- and slow-acidifying Strep. thermophilus and for the CO2-responsive L. bulgaricus, respectively. Notably, the shortage of ammonia nitrogen had more severe effects than that of CO2 on yogurt fermentation, even if coculture with L. bulgaricus masked the effect of urease deficiency. Our work established (1) that urease deficiency inhibits the fermentative acceleration of protocooperation regardless of the Strep. thermophilus and L. bulgaricus strain combinations, and (2) that urease is an essential factor for effective yogurt acidification.

Dates and versions

hal-02625831 , version 1 (26-05-2020)

Identifiers

Cite

R. Yamauchi, Emmanuelle Maguin, H. Horiuchi, M. Hosokawa, Y. Sasaki. The critical role of urease in yogurt fermentation with various combinations of streptococcus thermophilus and lactobacillus delbrueckii ssp. bulgaricus. Journal of Dairy Science, 2019, 102 (2), pp.1033-1043. ⟨10.3168/jds.2018-15192⟩. ⟨hal-02625831⟩
13 View
0 Download

Altmetric

Share

Gmail Facebook X LinkedIn More