Microbial community transfers across a pilot ripening cellar are driven by cheese wiping

Various biological agents (bacteria, moulds, yeasts...) contribute by their metabolic activity to the cheese's ripening. Cares performed on cheeses during ripening, like wiping, may disperse bioaerosols present on the cheeses rinds. Chronic inhalation of potential allergenic particles in ripening cellars may cause for operators the development of respiratory diseases as asthma. However, microorganisms' emissions and transfers across ripening cellars during cares remained poorly documented. Hence, to evaluate microorganisms transfer during cheese wiping, we focused on microbial community from long-ripened cheeses (CH_LR) and its dispersion in air (AR) and on short-ripened cheeses (CH_SR). Thirty-six Saint-Nectaire PDO cheeses (SR, LR), were stored and wiped or not wiped, in 3 experimental cellars (INRAE, Aurillac). Samples were taken over a period of 4 weeks in four environments: air, cellar walls, cheese cloths and cheese rinds. Levels of culturable bacteria and fungi were assessed by culturable-dependent analyses (n=92). Relative abundance of bacterial and fungal communities were analyzed by metabarcoding (16S RNA and ITS genes, respectively) (n=101 samples). Results showed an increase in airborne molds levels up to 7 log CFU/m3 of air during cheese wiping while out of wiping period levels of molds were around 2-3 log CFU/m3. Microbial profiles analyses revealed dominant species on CH_LR such as Mucor, Penicillium and Glutamicibacter species. Some of them were transferred to air, cheese cloths and cheese rinds. Wiping also contributed to the dispersion of less abundant genera on cheeses rinds such as Chrysosporium since its relative abundance in air was greater in the cellar where CH_LR were wiped.