Biodiversity of bacteriophages infecting Lactococcus lactis starter cultures.

In the current study, we characterized 137 Lactococcus lactis bacteriophages that had been isolated between 1997 and 2012 from whey samples obtained from industrial facilities located in 16 countries. Multiplex PCR grouping of these 137 phage isolates revealed that the majority (61.31%) belonged to the 936 group, with the remainder belonging to the P335 and c2 groups (23.36 and 15.33%, respectively). Restriction profile analysis of phage genomic DNA indicated a high degree of genetic diversity within this phage collection. Furthermore, based on a host-range survey of the phage collection using 113 dairy starter strains, we showed that the c2-group isolates exhibited a broader host range than isolates of the 936 and P335 groups.

Use of two autochthonous bacteriocinogenic strains as starter cultures in the production of salchichónes, a type of Spanish fermented sausages.

In this work, two autochthonous LAB strains (Lactiplantibacillus paraplantarum BPF2 and Pediococcus acidilactici ST6), isolated from spontaneously fermented sausages produced in Spain, were tested to produce Spanish fermented sausages (salchichón) in pilot plants, due to their promising technological and anti-listerial activity. These products were compared with a sample obtained with a commercial starter (RAP) and a spontaneously fermented control sample. Physico-chemical parameters, microbial counts, metagenomic analysis, biogenic amines content and organoleptic profile of the obtained samples were studied to assess the performances of the native starters. In fact, traditional and artisanal products obtained through spontaneous fermentations can represent an important biodiversity reservoir of strains to be exploited as new potential starter cultures, to improve the safety, quality and local differentiation of traditional products. The data underlined that ST6 strain resulted in a final lower percentage if compared with the other LAB used as starter cultures. The use of starters reduced the BA concentration observed in the sausages obtained with spontaneous fermentation and the BPF2 and ST6 strains were able to decrease the level of products rancidity. Moreover, a challenge test against L. monocytogenes were performed. The data confirmed the effectiveness in the inhibition of L. monocytogenes by the two bacteriocinogenic strains tested, with respect to RAP and control samples, highlighting their ability to produce bacteriocins in real food systems. This work demonstrated the promising application in meat industry of these autochthonous strains as starter cultures to improve sensory differentiation and recognizability of typical fermented sausages.

Debaryomyces hansenii Strains from Valle De Los Pedroches Iberian Dry Meat Products: Isolation, Identification, Characterization, and Selection for Starter Cultures.

Yeasts, filamentous fungi, and bacteria colonize the surface of fermented sausages during the ripening process. The source of this microbiota is their surrounding environment, and is influenced by the maturing conditions and starter cultures. Debaryomyces hansenii was previously isolated from several dry-cured meat products and associated with the lipolytic and proteolytic changes that occur in these products, influencing their taste and flavor. Therefore, this study isolated the yeast microbiota present in the casing from different meat products ("lomo," "chorizo," and "salchichón") from the Valle de los Pedroches region in southern Spain. D. hansenii was by far the most abundant species in each product, as all 22 selected isolates were identified as D. hansenii by biochemical and/or molecular methods. In contrast, no yeasts were found in the meat batter. These data constitute the first study of the yeasts present in "lomo" sausages and particularly the highly appreciated Valle de los Pedroches "lomo" sausages. Furthermore, the resistance of these isolates to different pHs, temperatures, and saline stress was studied, together with their catabolic characteristics. Based on the results, certain isolates are proposed as valuable candidate starter cultures that could improve both the manufacture and the flavor of such dry-cured meat products, and provide an understanding of new mechanisms involved in stress tolerance. Applied mediumscale industrial tests are currently in progress.

Characterization of Lactococcus lactis isolates from bovine mastitis.

Lactococcus lactis is a widely used mesophilic dairy starter and has been included in the Qualified Presumption of Safety (QPS) list of the European Food Safety Authority. However, it is increasingly found as the cause of human or animal infections, such as bovine mastitis, probably due to the improvement of the identification of the infective microorganisms. Since there are some grounds to suspect that at least certain variants of L. lactis may cause animal or human diseases, it is important to properly identify the differences between the strains associated with infections and the safe starter strains. Bovine mastitis isolates and dairy starter strains were genotypically characterized and clustered by the 16S rRNA gene sequence and RAPD-PCR fingerprint patterns, and phenotypically characterized by their tolerance to different stress conditions typically found in the intestinal tract of mammals, the carbohydrate- and antibiotic resistance profile, as well as the in vitro adhesion capacity to udder epithelial cells. Genotypically, there were no differences between the mastitis isolates and the dairy starter strains. However, there were clear phenotypic distinctions between mastitis isolates and typical starter strains, the former showing an increased tolerance to temperature, lysozyme, bile salts, pH and antibiotics, as well as improved carbohydrate fermentation capacity, and in vitro adhesion to udder epithelial cells. Although these differences might not be considered as actual virulence factors, they improve the ability of the strain to survive in the body of homeothermic animals and, interestingly, are also typical properties associated with potential probiotic strains.

Comparison between two selected Saccharomyces cerevisiae strains as fermentation starters in the production of traditional cachaça

Two Saccharomyces cerevisiae strains were tested as the starter yeasts in a traditional cachaça distillery. The strains used were S. cerevisiae UFMG-A829, isolated from a cachaça fermentation process, and S. cerevisiae K1-V1116, obtained from the wine industry. The permanence of each strain in the fermentation must was determined by RAPD (Random Amplified Polymorphic DNA)-PCR, with primer M13. Both yeast strains were prevalent in the vats for approximately 30 days. Indigenous non-Saccharomyces and indigenous S. cerevisiae strains were isolated in lower counts during the fermentation period. Indigenous S. cerevisiae strains were molecularly distinct when compared to the starter yeasts. The two yeasts appeared promising starter yeasts in the fermentation process to produce traditional cachaça.

Duas linhagens de Saccharomyces cerevisiae foram testadas como iniciadoras em uma destilaria de cachaça. Foram utilizadas as linhagens de S. cerevisiae UFMG-A829, isolada de fermentação de cachaça, e S. cerevisiae K1-V1116, de origem vinícola. A permanência de cada linhagem durante a fermentação foi determinada por RAPD (Random Amplified Polymorphic DNA)-PCR, utilizando o iniciador M13. As duas linhagens predominaram nas dornas de fermentação por aproximadamente 30 dias. Leveduras não-Saccharomyces e S. cerevisiae indígenas foram isoladas em menor proporção durante o experimento. As linhagens de S. cerevisiae indígenas apresentaram perfis moleculares distintos em relação às linhagens iniciadoras. As duas linhagens foram promissoras para serem utilizadas como iniciadoras do processo fermentativo para a produção da cachaça.