Metabolomics and gene-metabolite networks reveal the potential of Leuconostoc and Weissella strains as starter cultures in the manufacturing of bread without baker's yeast.

Lactic Acid Bacteria (LAB) could provide a valid alternative to S. cerevisiae as a starter culture for bakery products, avoiding yeast-related health problems while contributing to the technological and functional properties of bread. In this work, we evaluate the role of certain LABs (Leuconostoc citreum SB6, Weissella cibaria UC4051, Weissella confusa UC4051, and the commercial starter cultures Weissella cibaria, and Leuconostoc mesenteroides) in producing functional compounds (pro-technological, health-promoting, and postbiotic-like molecules). For this purpose, we analysed the genotypic and phenotypic features of strains, and we investigated dough fermentation from microbiological and metabolomics approaches. Results evidenced a clear discrimination between the metabolic activity of baker's yeast and LAB. The most discriminant metabolites derived from proteolysis and lipolysis, such as peptides, amino acids, and fatty acyls. Furthermore, we elucidated the different metabolism of these strains by building gene-metabolite interaction networks that pairwise compared the LAB strains of the same genus. While most of the networks showed a characteristic nucleotide metabolism, only the commercial W. cibaria exhibited an interaction network composed of amino acids and their related genes. In conclusion, our findings reveal that LAB strains under investigation, and particularly the commercial W. cibaria, can enhance the functional properties of bread.

Identification of small peptides arising from hydrolysis of meat proteins in dry fermented sausages.

In this study, proteolysis and low molecular weight (LMW) peptides (<3kDa) from commercial Argentinean fermented sausages were characterized by applying a peptidomic approach. Protein profiles and peptides obtained by Tricine-SDS-PAGE and RP-HPLC-MS, respectively, allowed distinguishing two different types of fermented sausages, although no specific biomarkers relating to commercial brands or quality were recognized. From electrophoresis, α-actin, myoglobin, creatine kinase M-type and L-lactate dehydrogenase were degraded at different intensities. In addition, a partial characterization of fermented sausage peptidome through the identification of 36 peptides, in the range of 1000-2100 Da, arising from sarcoplasmic (28) and myofibrillar (8) proteins was achieved. These peptides had been originated from α-actin, myoglobin, and creatine kinase M-type, but also from the hydrolysis of other proteins not previously reported. Although muscle enzymes exerted a major role on peptidogenesis, microbial contribution cannot be excluded as it was postulated herein. This work represents a first peptidomic approach for fermented sausages, thereby providing a baseline to define key peptides acting as potential biomarkers.

Proteomic and peptidomic insights on myofibrillar protein hydrolysis in a sausage model during fermentation with autochthonous starter cultures.

The hydrolysis of myofibrillar proteins during fermentation of sausage models by an autochthonous starter culture was investigated. In order to provide a whole map of the generated products, proteomic and peptidomic were used and complemented with the amino acid profile. Beaker sausages (BS) were used as models which were inoculated or not with Lactobacillus curvatus CRL705 and Staphylococcus vitulinus GV318 as starter cultures. The hydrolysis of actin, myosin light chain 1/3 (MLC 1/3), myosin regulatory light chain-2 (MRLC-2) and myosin heavy chain (MHC) was evidenced by two-dimensional gel electrophoresis (2-DE). In addition, a total of 33 peptides arisen from troponin T, MRLC-2 and particularly from actin were identified by LC-MS/MS. These results showed that the starter culture significantly enhanced the proteolysis of the proteins named above, even when the endogenous enzymes induced a clear breakdown. L. curvatus CRL705 highly enriched both peptide pattern and amino acid concentrations. When the autochthonous starter culture was inoculated, although proteolysis was remarkably reinforced, a reduction in peptide and amino acid composition was observed. Regarding actin primary structure, three regions of this protein were highly susceptible to degradation by the starter culture. Additionally, the essential role of exopeptidases - from meat and bacteria - in diversity of actin peptides during fermentation was shown. This study improved the knowledge of the proteolysis of myofibrillar proteins and the involved enzymes, as well as, completed the previously reported degradation of sarcoplasmic proteins by the same autochthonous starter culture. The singular peptides and amino acids pattern generated might contribute to the uniqueness of produced fermented sausages while they may be used as quality markers.