Streptococcus thermophilus is a common and beneficial bacterium found in various natural environments, particularly recognized for its widespread use in food production. This microorganism is a valuable component in many fermented products, playing a significant role in their creation and offering advantages to human health.
Understanding Streptococcus Thermophilus
Streptococcus thermophilus is a Gram-positive bacterium, which means its cell wall structure retains a crystal violet stain used in a common laboratory test. It is a facultative anaerobe, capable of growing in both the presence and absence of oxygen, though it typically thrives in microaerophilic conditions. Morphologically, this bacterium is spherical (coccus-shaped) and often arranges itself in chains or pairs. This bacterium is also classified as a lactic acid bacterium, signifying its ability to produce lactic acid as a primary metabolic end-product. Streptococcus thermophilus is thermophilic, meaning it prefers and grows optimally at high temperatures, typically between 35°C and 45°C.
Its Crucial Role in Dairy Products
Streptococcus thermophilus is one of the most widely used bacteria in the dairy industry, serving as a key starter culture in the production of various fermented milk products. Its primary function involves the fermentation of lactose, the natural sugar found in milk. During this process, Streptococcus thermophilus converts lactose into lactic acid. This lactic acid production is essential as it lowers the pH of the milk, causing the milk proteins (casein) to coagulate and thicken.
This acidification contributes significantly to the characteristic texture, tangy flavor, and preservation of dairy products. It is a standard component in yogurt production, often used in conjunction with Lactobacillus delbrueckii subsp. bulgaricus. The synergistic relationship between these two bacteria is important; Streptococcus thermophilus grows faster initially, producing acid that creates an optimal environment for L. bulgaricus to flourish. Beyond yogurt, it is also utilized in the manufacturing of various cheeses, including mozzarella, cheddar, and Swiss-type cheeses.
Beneficial Effects on Human Health
When consumed, Streptococcus thermophilus acts as a probiotic, contributing to several health benefits, particularly concerning digestive health. One significant advantage is its ability to aid in lactose digestion for individuals with lactose intolerance. This bacterium produces the enzyme beta-galactosidase (lactase), which breaks down lactose into more easily digestible sugars, glucose and galactose, thereby reducing symptoms like bloating and gas.
Furthermore, Streptococcus thermophilus contributes to overall gut health by helping to maintain a balanced gut microbiota. It can help inhibit the growth of certain harmful bacteria by competing for nutrients and space, and by producing lactic acid which creates an unfavorable environment for pathogens. Research also suggests its potential role in supporting the immune system, primarily by modulating gut microbiota and enhancing the gut barrier function. It may also help reduce gut inflammation.
Distinguishing From Harmful Bacteria
The name “Streptococcus” can sometimes cause confusion due to its association with pathogenic bacteria, such as Streptococcus pyogenes, which causes strep throat. However, Streptococcus thermophilus is a distinct and non-pathogenic species. It has evolved separately from harmful Streptococcus species, and its genome lacks the virulence-related genes found in pathogenic strains.
Unlike its pathogenic relatives, Streptococcus thermophilus is considered a safe microorganism for consumption and has been granted “Generally Recognized as Safe” (GRAS) status by the FDA. This designation reflects its long history of safe use in the food industry. Its role is beneficial, contributing to food production and human well-being, rather than causing illness.