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

Various biological agents (bacteria, molds, yeasts …) contribute by their metabolic activity to cheese's ripening. Cheese care procedures during ripening, like wiping, may disperse microorganisms from cheese rinds. Chronic inhalation of potential allergenic particles in ripening cellars may cause, for operators, development of respiratory diseases as asthma. However, microorganisms' emissions and transfers across ripening cellars during cares remained poorly documented. To evaluate microorganisms transfer consecutive to cheese wiping, we focused on microbial community from long-ripened cheeses (CH_LR) and its dispersion in air and on short-ripened cheeses (CH_SR). Twenty-four short-ripened cheeses, all wiped, were distributed into 3 experimental cellars (INRAE, Aurillac), two of which also received 6 long-ripened cheeses either wiped (cellar 2) or unwiped (cellar 3). Samples were taken over a period of 4 weeks in four environments: cheese rinds, cheese cloths, air and cellar walls. Levels of culturable microorganisms were assessed (n = 92). Microbial community compositions were analyzed by metabarcoding (16S rRNA and ITS genes, respectively) (n = 100 samples). Results showed an increase in airborne mold levels up to 7 log CFU. m^-3 of air during cheese wiping, compared to 2-3 log CFU. m^-3 without wiping activity. Microbial profiles analyses revealed dominant species on CH_LR such as Mucor, Penicillium and Glutamicibacter sp. In CH_LR, Glutamicibacter sp. (60 %), Mucor sp and Penicillium sp (50 % altogether), were transferred to air (respectively 60 % for Glutamicibacter sp and 90 % for both fungal species), cheese cloths and CH_SR. Wiping of CH_LR also contributed to the dispersion in air of less abundant genera of interest for cheese ripening like Chrysosporium (<10 %).