Streptococcus thermophilus urease activity boosts Lactobacillus delbrueckii subsp. bulgaricus homolactic fermentation.


The proto-cooperation between Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus in the yogurt consortium enhances the growth rate and size of each population. In contrast, the independent growth of the two species in milk leads to a slower growth rate and a smaller population size. In this study, we report the first evidence that the urease activity of S. thermophilus increases the intracellular pH of L. delbrueckii in the absence of carbon source. However, in milk, in the presence of lactose the alkalizing effect of urea-derived ammonia was not detectable. Nevertheless, based on glucose consumption and lactic acid production at different pHin, L. delbrueckii showed an optimum of glycolysis and homolactic fermentation at alkaline pH values. In milk, we observed that ammonia provided by urea hydrolysis boosted lactic acid production in S. thermophilus and in L. delbrueckii when the species were grown alone or in combination. Therefore, we propose that urease activity acts as an altruistic cooperative trait, which is costly for urease-positive individuals but provides a local benefit because other individuals can take advantage of urease-dependent ammonia release.


PubMed ID: 26826763

Projects: YogurtDesign

Journal: Int J Food Microbiol

Citation: Int J Food Microbiol. 2017 Apr 17;247:55-64. doi: 10.1016/j.ijfoodmicro.2016.01.006. Epub 2016 Jan 20.

Date Published: No date defined

Authors: S. Arioli, G. Della Scala, M. C. Remagni, M. Stuknyte, S. Colombo, S. Guglielmetti, I. De Noni, E. Ragg, D. Mora

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Created: 12th Oct 2018 at 10:13

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