Difference between Yeast and Mold

By: | Updated: Jan-25, 2018

Yeasts and Molds both belong to the fungus kingdom. Oftentimes, when we say fungus, there is a host of negative associations that come with it. But the truth is, certain types of yeasts and molds are beneficial and useful to us in many ways. Read on and discover all about them and the characteristics that set them apart.

Summary Table

Yeast Mold
Single-celled microorganismsGrows in multicellular strands
There are 1,500 known speciesThere are 1,000 known species
White and usually oval-shapedCan appear in different colors and shapes
Can be found in plant leaves, fruits, soil, skin and intestinal tract of animalsAppears in dark, damp areas
Mostly used in making alcoholic beverages and as a baking ingredientUsed in food production and pharmaceutical products
Can cause infections among those with poor immune systemCan cause allergic reactions


Yeast fermentation producing an alcoholic beverage

Yeasts are single-celled microorganisms classified as fungi. There are 1,500 known species of yeasts. These microorganisms are usually white and oval-shaped. They are common in our environment and can be found almost anywhere. Naturally occurring yeasts are present in plants and animals, also among insects and in the soil. Other types of yeasts are cultured and grown in laboratories. The word “yeast” comes from the Old English word “gist” and the Indo-European root yes- which means “foam” or “bubble.”

Yeast is widely used in baking, as a leavening agent. Setting aside the dough for some time allows the yeast to release carbon dioxide, thus making the dough rise. Yeast is also used in the fermentation of simple sugars to produce alcoholic beverages.

Yeast infection, which is a fungal infection, can also occur among people with poor immune systems. This affects different body parts and can cause irritation and severe itchiness.

cheese with mold
Cheese with blue-grey mold

Molds are a type of fungi which grow in multicellular strands that are called hyphae. There are 1,000 known species of molds. Molds usually thrive in dark, damp areas. Mold spores are all around us. They grow when they land on damp surfaces. The growth of molds depends on the amount of moisture in the air due to the level of humidity. When molds grow on food or certain surfaces, discoloration occurs accompanied by a pungent smell.

Molds are used to culture cheese such as brie and blue cheese. The antibiotic penicillin, as well as other drugs, can also be derived from molds. However, mold spores are also notorious for causing allergies. They can get into the nose, reach the lungs, and cause asthma attacks.

Yeast vs Mold

What is the difference between yeast and mold? Yeasts are single-celled microorganisms while molds are multicellular organisms. There are 1,500 known species of yeasts which is more than the 1,000 identified species of molds. When checked under a microscope, yeasts are white and oval-shaped. Molds appear in different colors and shapes. Yeasts and molds can be found everywhere. Naturally occurring yeasts are present in the soil, in insects, in plant leaves and also on the skin and in the intestinal tract of animals. Molds grow mostly in dark, damp areas. Yeast is essential in the production of alcoholic beverages and is a widely used baking ingredient. Molds, on the other hand, are commonly used to culture cheese and to produce the antibiotic penicillin. Yeast infections occur among people with poor immune systems whereas mold spores can cause allergic reactions for some people.

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