hiivoja

Hiivoja are a broad group of unicellular fungi that play a central role in fermentation and food production. In Finnish, hiiva refers to yeast, and hiivoja denotes yeasts in general. They are eukaryotic microorganisms, typically oval or round, that reproduce mainly by budding, though some species divide by fission. Yeasts metabolize sugars and can grow under aerobic or anaerobic conditions.

The economically most important yeasts belong to the genus Saccharomyces. Saccharomyces cerevisiae is widely used to leaven bread and to produce ethanol in beverages. Saccharomyces pastorianus is used for lager beer. Other non-Saccharomyces yeasts are also important in wine, dairy, and biotechnology. Some species, notably Candida, can be opportunistic pathogens in humans.

In metabolism, yeasts ferment sugars to ethanol and carbon dioxide when oxygen is limited, and they can also respire aerobically. Growth temperatures for many food-related yeasts lie roughly between 20 and 30°C, with variations by species. Yeast cells reproduce by budding, forming daughter cells that separate or form short chains in certain conditions.

Applications extend beyond baking and brewing to winemaking, biofuel production, and biotechnological processes. Some strains, such as Saccharomyces boulardii, are marketed as probiotic supplements, while others are maintained as safe food-grade cultures for fermentation.

Ecology and safety: Yeasts are widespread in nature, inhabiting fruits, plant surfaces, soil, and animal guts. They can cause spoilage by fermenting sugars in juices or dairy products. Most industrial and culinary yeasts are considered safe, but some species may cause opportunistic infections; proper handling and storage reduce risks.