Microbial multiomics approach in understanding blue-veined cheeses bitterness

Blue-veined cheeses are regularly described as bitter but links between microbial diversity, function, gene expression and bitterness have not been deciphered yet. In the present work, microbiological, biochemical, metabarcoding (amplicons sequencing), metagenomic (DNA-Seq) and metatranscriptomic (RNA-Seq) were combined to better understand the potential origins of excessive bitterness in semi-soft blue-veined PDO Bleu d'Auvergne cheeses by exploring microbial composition, function, expression, conjugated to physico-chemical analysis and sensorial analysis. Physicochemical analyses revealed significative cheese bitterness differences associated with multiples factors in milk and in several cheeses' parameters. After 30 days of ripening, Low Bitter (LB) cheeses were characterized by a higher bacterial and yeasts richness and diversity while High Bitter (HB) cheeses were characterized by one most dominant filamentous fungus Penicillium roqueforti and one most dominant bacterial species Lactococcus lactis. It affected in return the use of resources presents in milk through preferential mobilization of metabolic pathways as fatty acid desaturation (HB) and fatty acid biosynthesis (LB). Increase of salt concentration modulated the microbial community which withstood with osmostress. Abundance, richness, diversity of bacteria, eukaryote especially yeasts, phages and mycovirus were differentially involved in resources utilization from milk proteins, regulating cheese bitterness.