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Algerian couscous named lemzeiet is manufactured from fermented wheat. Historically performedin underground silos called matmor, the fermentation of wheat is now generally carried out in plastic jerrycans withor without addition of vinegar at the beginning of the fermentation. Culture-dependent and culture-independentmethods (PCR-TTGE) were used to characterize lactic acid bacteria and to determine their dynamic and diversity over a two-year period, with and without the addition of vinegar.Fungi, physicochemical characteristics, and volatile compoundprofiles were also monitored. The isolates obtained from different stages of fermentation and from both processes were characterized by coupling different molecular methods (16SrRNA/pheS/rpoA gene sequencing, speciesspecific PCR, RAPD and PFGE). PCR-TTGE revealed very similar profiles for both processes. Sixty-nine isolates were identified as belonging to six genera of 16 species(Enterococcus, Lactobacillus, Leuconostoc, Pediococcus, Weissella, and Streptococcus). The profiles of volatile aroma compounds showed a marked effect of the fermentation process, compared to non-fermented wheat, with 35 of the 40 volatiles detected at amounts 20- to 30-fold higher in fermented wheat samples. This study gives the first insight into lactic acid bacteria population diversity and activity in fermented wheat and will contribute to a better control of the fermentation process

Propionibacterium freudenreichii is widely used in Swiss-type cheese manufacture, where it contributes to flavour and eye development. It is currently divided into two subspecies, according to the phenotype for lactose fermentation and nitrate reduction (lac+/nit− and lac−/nit+ for P. freudenreichii subsp. shermanii and subsp. freudenreichii, respectively). However, the existence of unclassifiable strains (lac+/nit+ and lac−/nit−) has also been reported. The aim of this study was to revisit the relevance of the subdivision of P. freudenreichii into subspecies, by confirming the existence of unclassifiable strains. Relevant conditions to test the ability of P. freudenreichii for lactose fermentation and nitrate reduction were first determined, by using 10 sequenced strains, in which the presence or absence of the lactose and nitrate genomic islands were known. We also determined whether the subdivision based on lac/nit phenotype was related to other phenotypic properties of interest in cheese manufacture, in this case, the production of aroma compounds, analysed by gas chromatography-mass spectrometry, for a total of 28 strains. The results showed that a too short incubation time can lead to false negative for lactose fermentation and nitrate reduction. They confirmed the existence of four lac/nit phenotypes instead of the two expected, thus leading to 13 unclassifiable strains out of the 28 characterized (7 lac+/nit+ and 6 lac−/nit−). The production of the 15 aroma compounds detected in all cultures varied more within a lac/nit phenotype (up to 20 times) than between them. Taken together, these results demonstrate that the division of P. freudenreichii into two subspecies does not appear to be relevant.