Microbial Profiling of Smear-Ripened Cheeses: Identification of Starter Cultures and Environmental Microbiota

Smear-ripened cheeses are distinguished by their complex microbiota, which play an important role in ripening, flavour development, texture and microbiological safety. Although commercial production typically relies on defined starter and adjunct cultures, microorganisms from the production environment may also shape the product’s characteristics. This study examined the microbial composition of smear-ripened cheeses from six commercial manufacturers using culture and culture-independent techniques, including 16S rRNA gene sequencing and sequencing of internal transcribed spacers. A limited number of microorganisms was recovered by culture, with 37 different isolates identified across all samples. Sequencing of the 16S rRNA gene and internal transcribed spacers revealed 75 and 7 distinct operational taxonomic units, respectively. The microbiota composition reflected the contribution of both mesophilic and thermophilic starter and adjunct cultures, alongside microorganisms originating from the production environment. These included various psychrotrophic bacteria, marine (i.e., osmotolerant) bacteria, and other halophiles from Proteobacteria (Psychrobacter, Pseudoalteromonas, Marinomonas, and Vibrio), Firmicutes (Vagococcus and Marinilactibacillus), Actinobacteriota (Glutamicibacter), Bacteroidota (Winogradskyella and Brumimicrobium), Campylobacterota (Malaciobacter) and Fusobacteriota (Psychrilyobacter) specific to the environment of particular manufacturers. The results indicate that, although pasteurised milk and defined starter cultures are used in commercial production, microorganisms originating from the cheese factory environment form a substantial part of the microbiota of smear-ripened cheese.