The role of cheese microbial ecosystems is dominant when considering the conversion of the curd gels to the diversity of colours, textures and flavours of ripened cheeses. In the last 10 years, genomic and metagenomic applied to cheeses was able to demonstrate the repeated occurrence of an unexpected diversity of yeasts and moulds, Gram + but also Gram – bacteria (1). Soft cheeses with high surface/volume ratio will mainly be considered here.
Interactions between the microbial ecosystem and the curd includes adaptation to the cheese pH, low temperature, salt content but also adaptation to low iron concentrations (2). The genomic analyses were able to throw light on the adaptation of micro-organisms to cheese environments as compared to close species from other environments.
However, the interactions between species in the ecosystems are also important. The impact of species omissions in reconstituted cheese ecosystems easily demonstrated biological interactions, but decifering the biochemical mechanisms involved is difficult. This knowledge will be decisive in improving the control of the ecosystem resistance to avoid microbial alterations and help to improve the resilience of the system in case of troubleshooting during the cheese production process.
Some species are efficiently producing flavours and among them sulfur compounds. Decifering their metabolism by transcriptomic and metabolomic helped to understand the physiological context of these productions at the molecular level in pure and mixed cultures (3,4).
The use of new species when their functionalities look interesting as ripening starters are motivating but questionable. However, at least, understanding of the key parameters driving these ecosystems could help select ripening strains more fitted to cheese technologies and consequently help prevent troubles.