Enzymes showing differences in protein (*) or transcript abundance for L. rhamnosus PR1019 grown in CB compared to MRS are highlighted. Dark green, expression ratio CB versus MRS 5 to 10; light green, expression ratio CB versus MRS < 5. Transcript data are from the present study. Protein data are from

Bove et al. [16]. To our knowledge, this is the first evidence of activation of the POX pathway in L. rhamnosus. On the contrary, POX activity has been extensively described to date in L. plantarum and involved with acetate production in its survival during the stationary phase check details of aerobic growth [35–39]. In particular, accumulation of acetate instead of lactate is thought to play a role in ensuring the pH homeostasis with an overall beneficial effect for the cell [37, 40]. The additional ATP generated via ACK has been shown to enhance the biomass production [41]. Interestingly,

Lorquet et al. [37] showed that in the late stationary phase, when the production of acetate stopped, an OD decrease resulting from lytic processes occurred. The hypothesis is that in the absence of ATP production, protons can no longer be extruded by ATPases with a consequent dissipation of the https://www.selleckchem.com/products/NVP-AUY922.html proton motive force, which has been shown to be one of the mechanisms triggering autolysis of gram-positive bacteria. Interestingly, high levels of acetic acid and low levels of lactic Carteolol HCl acid have been recently observed in L. rhamnosus strains grown in CB under the same conditions of our study [16, 42] Furthermore, by a proteomic approach, Bove et al. [16] showed an increase in expression of PTA and ACK, which are involved in the synthesis

of acetic acid in a branch of the pyruvate metabolism other than POX pathway (Figure 2), during L. rhamnosus growth in CB compared to MRS. Highlighting a possible alternative route of degradation of pyruvate to acetate (the POX pathway; Figure 2), our transcriptomic results seem to complement data from proteomics, strengthening the hypothesis that L. rhamnosus can utilize pyruvate as a growth substrate during cheese ripening. Pyruvate is an intracellular metabolite that could be produced through different find more metabolic routes using the carbon sources present in cheese (i.e. through metabolism of citrate, lactate, amino acids, and nucleotides). Moreover, pyruvate can be released in the cheese matrix with starter lysis. Liu et al. [43] showed that the activity of POX in L. plantarum could be related to the catabolism of L-serine. According to the authors, L-serine is deaminated via a serine dehydratase into pyruvate, which is subsequently converted into acetate by the POX enzyme [43]. Pyruvate conversion by POX has been recently supposed also in L. casei[44].