Project description:The intra sub-species diversity of six strains of Lactococcus lactis subsp. lactis was investigated at the genomic level and in terms of phenotypic and transcriptomic profiles in UF-cheese model. Six strains were isolated from various sources, but all are exhibiting a dairy phenotype. Our results showed that, the six strains exhibited small phenotypic differences since similar behaviour in terms of growth was obtained during cheese ripening while only different acidification capability was detected. Even if all strains displayed high genomic similarities, sharing a high core genome of almost two thousands genes, the expression of this core genome directly in the cheese matrix revealed major strain-specific differences. This strains with the same dairy origin.
Project description:RNA-seq was used in combination with various analytical chemistry approaches to identify the chemical and genetic basis of pigment production of the bacterium Glutamicibacter arilaitensis when growing on cheese. This bacterium commonly found in cheese rinds where it co-occurs with Penicillium species and other molds. Pinkish-red pigments are produced by the bacterium in response to growth with Penicillium. Both chemical analyses and RNA-seq point to coproporphyrin III as the major metabolite leading to pigment formation.
Project description:This study investigated the impact of individual lactococcal starter cultures on peptide formation and bitter peptide accumulation during cheese aging using a novel mini-scale cheese production system. Cheeses were produced using single-strain fermentations of Lactococcus lactis and Lactococcus cremoris and aged for 45 and 90 days. Peptide profiles were analyzed using LC-MS/MS-based peptidomics to characterize strain-specific proteolytic patterns and bitter peptide generation from casein proteins. The resulting peptide profiles demonstrated strong strain specificity and reproducibility among replicates. Particular emphasis was placed on bitter peptides derived from β-casein and αS1-casein regions associated with cheese bitterness. Two L. lactis strains, E2-4M12 and E1-6M12, consistently produced lower abundances of bitter peptides despite substantial overall peptide abundance, suggesting unique proteolytic characteristics. Comparative analysis between CEP-positive and CEP-negative strains indicated that CEP genotype alone was not a primary determinant of bitter peptide accumulation. These findings contribute to understanding how starter culture selection influences cheese proteolysis and bitterness development during ripening.