Brevibacterium’s Roles in Cheese Maturation and Skin Odors

Brevibacterium plays a crucial role in both the food industry and human biology. It is best known for its contribution to the maturation of certain cheeses, where it influences texture and imparts distinctive aromas. Interestingly, this same bacterium is also associated with human skin, particularly in odor production, due to its metabolic activities.

Taxonomy And Morphological Features

Brevibacterium belongs to the phylum Actinobacteria, known for its high G+C content and diverse metabolism. It is classified under the family Brevibacteriaceae, with Brevibacterium linens being the most well-known species due to its role in cheese maturation. This Gram-positive, non-motile bacterium typically forms short rods or coccobacilli, distinguishing it from other Actinobacteria.

Its cell wall, rich in peptidoglycan with meso-diaminopimelic acid, provides structural integrity and resistance to environmental stress. Unlike many Actinobacteria, Brevibacterium does not form spores, relying on its robust cell envelope. Its colonies often display orange to pink pigmentation due to carotenoid production, which protects against oxidative damage. This pigmentation is particularly evident on cheese rinds, where Brevibacterium thrives.

Metabolically, Brevibacterium is an obligate aerobe that utilizes amino acids and fatty acids, producing volatile sulfur compounds like methanethiol and dimethyl disulfide. These compounds contribute to the characteristic aroma of washed-rind cheeses. The bacterium secretes proteases and lipases, facilitating protein and lipid breakdown, which enhances its industrial and ecological significance.

Natural Habitats And Environmental Presence

Brevibacterium thrives in protein-rich environments, metabolizing amino acids and organic substrates. It is found in both natural and human-influenced settings, colonizing organic surfaces that support microbial communities. In soil, it aids in the decomposition of complex organic matter, contributing to nitrogen and sulfur cycling. Its ability to break down keratinous material allows it to colonize decomposing proteins, such as animal remains and feather waste, making it a key player in nutrient recycling.

Beyond soil, Brevibacterium is found in marine and freshwater habitats, where organic deposits provide a suitable niche. It has been identified in aquatic biofilms, playing a role in organic matter breakdown. In fish-processing environments, it thrives on protein-rich surfaces, demonstrating resilience to fluctuating moisture and salinity.

Human-associated environments also support Brevibacterium, particularly on textiles, where sweat and skin cells create a conducive microenvironment. It persists on clothing, especially in humid conditions, underscoring its adaptability to anthropogenic settings and its role in microbial communities.

Enzymatic Activities In Maturation Processes

Brevibacterium is essential to the maturation of washed-rind cheeses, transforming texture and flavor through enzymatic activity. As it colonizes the cheese surface, it secretes proteolytic enzymes that degrade casein, softening the cheese interior. This process generates peptides and free amino acids, contributing to savory and umami flavors. The resulting creamy consistency is characteristic of cheeses like Limburger and Époisses.

Lipolytic enzymes hydrolyze milk fat into free fatty acids, which serve as precursors for aromatic compounds. Short-chain fatty acids, such as butyric and isovaleric acids, contribute to the pungent notes of aged cheeses. These compounds interact with sulfur-containing metabolites, intensifying the distinctive aroma of washed-rind varieties.

Brevibacterium also degrades methionine, producing volatile sulfur compounds such as methanethiol, dimethyl disulfide, and dimethyl trisulfide. These molecules contribute to the strong scent of mature cheeses. Controlled bacterial growth on cheese rinds ensures a balanced biochemical transformation, preventing unwanted bitterness or off-flavors.

Interaction With Skin And Possible Odor Formation

Brevibacterium naturally inhabits human skin, particularly in moisture-rich areas like the feet, underarms, and groin. It thrives on amino acids, lipids, and other organic compounds present in sweat and sebaceous secretions. As it metabolizes these compounds, it generates volatile molecules, including methanethiol, which imparts a strong, cheese-like scent.

Its interaction with other skin microbiota, such as Staphylococcus and Corynebacterium, further influences odor formation. These bacteria contribute to the breakdown of sweat components, producing organic acids, sulfur compounds, and aldehydes. Environmental factors like humidity, hygiene, and clothing materials affect bacterial growth and odor intensity.

Laboratory Identification And Cultivation

Isolating Brevibacterium in laboratory settings requires selective media that support its metabolic needs while inhibiting competing microbes. Agar plates with high salt concentrations or proteinaceous substrates are commonly used. As an obligate aerobe, it requires oxygen-rich conditions, with optimal growth temperatures between 20°C and 30°C. Its colonies exhibit distinctive orange to pink pigmentation, aiding identification.

Confirmatory identification involves biochemical and molecular techniques. Gram staining reveals its Gram-positive cell wall, while catalase and oxidase tests characterize its metabolism. Advanced methods like 16S rRNA gene sequencing ensure precise species classification. In cheese production, controlled cultivation maintains specific pH and moisture levels to optimize enzymatic activity. Long-term storage is achieved through cryopreservation or lyophilization, preserving viable cultures for research and industrial use.