Perfil metagenômico durante a maturação de queijo elaborado com "pingo" e a influência da sua microbiota sobre Staphylococcus aureus

Abstract

Artisanal Minas Cheese (QMA) is a traditional product from Minas Gerais, produced with raw milk and endogenous starter culture ("pingo"), whose microbiota directly influences its ripening, sensory quality, and microbiological safety. This study characterized the metataxonomic profile of a cheese analogous to QMA (QAQMA), produced from the "pingo" of a farm in the Campo das Vertentes region, under controlled conditions, throughout 22 days of ripening. Sixteen cheeses were produced, control (n=8) and inoculated (n=8). The control cheese was prepared in the traditional way, while the inoculated cheese was prepared with raw milk inoculated with 108 CFU/g of S. aureus. The influence of the autochthonous microbiota from the ―pingo‖ on Staphylococcus aureus was evaluated at four ripening times (0, 7, 14, and 22 days) by culture-dependent microbiological, physicochemical, and metataxonomic methods, from the sequencing of the V3-V4 region of the 16S rRNA. The physicochemical analyses showed a significant reduction in moisture (45.96% to 19.35%), and a pH variation between 6.79 and 6.86. The chloride content did not vary significantly during the ripening of the cheeses. The extension and depth of proteolysis indexes increased throughout ripening, indicating greater protein degradation and evolution of the ripening process. The milk microbiota was dominated by Pseudomonas, Serratia, and Lactococcus, while the "pingo" and the control cheese contained predominantly Lactococcus lactis (>92%). Some genera, such as Weissella, were observed only in the cheese, while others, such as Lactobacillus, were identified only in the "pingo" and cheese. The alpha diversity analysis pointed to the dominance of a few species, with L. lactis being predominant in the control cheese and L. lactis + S. aureus in the inoculated cheese. Beta diversity pointed to structural changes in the microbiota throughout ripening. The UniFrac distance evaluation pointed to milk as the most distinct sample, while the control cheese presented a community with low variation over time, unlike the inoculated group, which showed a gradual reduction of Staphylococcus and an increase of L. lactis. An increase in the similarity between the microbiotas of the inoculated and control cheese was observed, possibly due to the progressive replacement of S. aureus by Lactococcus. The PCoA (Bray-Curtis) indicated greater dispersion of the microbial community in the inoculated cheese, suggesting variations in the microbiota throughout ripening. The "pingo" microbiota showed moderate similarity with the microbiotas of the control and inoculated cheese, while the milk maintained a unique profile. The results suggest that ripening acts as a selective factor, reducing diversity and favoring the selection of L. lactis. The high presence of L. lactis in the cheese indicates a bioprotective effect, favoring the inhibition of S. aureus. The increase in proteolysis indexes associated with the selection of lactic acid bacteria reinforces the influence of the autochthonous microbiota on the ripening of QAQMA.