Microbial transfers from permanent grassland ecosystems to milk in dairy farms in the Comté cheese area.

The specificity of dairy Protected Designation of Origin (PDO) products is related to their "terroir" of production. This relationship needs better understanding for efficient and sustainable productions preserving the agroecological equilibrium of agroecosystems, especially grasslands. Specificity of PDO Comté cheese was related to the diversity of natural raw milk bacterial communities, but their sources need to be determined. It is hypothesized that raw milk indigenous microbial communities may originate from permanent grazed grasslands by the intermediate of dairy cows according to the sequence soil-phyllosphere-teat-milk. This hypothesis was evaluated on a 44 dairy farms network across PDO Comté cheese area by characterizing prokaryotic and fungal communities of these compartments by metabarcoding analysis (16S rRNA gene: V3-V4 region, 18S rRNA gene: V7-V8 region). Strong and significant links were highlighted between the four compartments through a network analysis (0.34 < r < 0.58), and were modulated by soil pH, plant diversity and elevation; but also by farming practices: organic fertilization levels, cattle intensity and cow-teat care. This causal relationship suggests that microbial diversity of agroecosystems is a key player in relating a PDO product to its "terroir"; this under the dependency of farming practices. Altogether, this makes the "terroir" even more local and needs to be considered for production sustainability.

Preliminary characterization of microflora of Comté cheese.

The evolution of the microflora of three Comté cheeses made in duplicate with raw milk from three different sources was followed during ripening. The same starter was used with each type of milk. The comparison of the cheeses did not reveal any significant difference in the development of the microflora. Starter lactic acid bacteria (Streptococcus thermophilus and Lactobacillus helveticus), which are added at the beginning of manufacture, decreased quickly in the first stages of ripening supporting the hypothesis of cell autolysis. Other microorganisms, i.e. homofermentative and heterofermentative lactobacilli (Lact. delbrueckii ssp. lactis, Lact. paracasei ssp. paracasei, Lact. rhamnosus and Lact. fermentum), pediococci, enterococci and propionibacteria grew in cheese from small numbers in fresh curd. The characterization of Strep. thermophilus by pulsed-field gel electrophoresis showed that wild strains were also able to grow in the curd. The values for the genome size of 11 Strep. thermophilus strains determined in this investigation were in the range of 1.8-2.3 Mbp. The potential role of starter and raw milk microflora in cheese flavour development was considered.