By: - Updated: February 11, 2019

Aspergillus Niger

What does canned fruit, shampoo, and blood preservation have in common?

Yup, you guessed it. Aspergillus Niger is used in citric acid production which, in turn, is used as preservative and flavoring agent in a wide range of commonly used products. Although modern blood preservation methods involve separating different components and storing each in a suitable way, citrate-phosphate dextrose is still part of the process.

What is Aspergillus Niger?

The filamentous fungus Aspergillus Niger is a type of mold and the most common fungus in the Aspergillus family. The word Aspergillus is derived from the Latin word “aspergillum” which basically means “holy water sprinkler”. When viewed under a microscope, these fungi resemble the shape of these sprinklers and so they were named.

Aspergillus niger prepared using th -freeze drying method
Aspergillus niger prepared using the freeze drying method

Groups of Aspergillus were initially divided according to spore color, and most with brown to black spores fell under the A. niger group. However, there are so many differences between these Aspergilli that most of them are actually classified as a different species. In addition to this, there are an abundance of strains of A. niger which differ widely in shape and ability.

The History of Aspergillus Niger

Aspergillus Niger can be simply cultivated in a lab and has therefore been the subject of extensive research. A food chemist called James Currie made an interesting discovery in 1917—any strain of A. niger produces high concentrations of citric acid when cultivated in a sugar medium.

Citric acid has immense value in many industries:

  • It’s the main souring agent in the food and beverage industries
  • In the cosmetics industry it’s used as an antioxidant and as a buffer for pH adjustments
  • The pharmaceutical industry used to use iron citrate as a source of iron and citric acid to preserve stored blood

After Currie’s discovery, in 1919, A. niger became a regular part of industrial-level production and the biochemical fermentation industry began to flourish. As a result, industrial biotechnology was born.

Now, producing citric acid by Aspergillus Niger fermentation is a multi-billion-dollar industry. A. niger is not only used in citric acid production, but also bring about various proteins, enzymes and secondary metabolites.

Is Aspergillus Niger Dangerous?

In contrast with other Aspergillus species, Aspergillus Niger is unlikely to cause human illness. It contains several toxins, and while most are completely harmless, some may prove dangerous to certain individuals. Multiple animal studies resulted in no negative health effects both when inhaled and consumed. It’s a food spoilage organism and the cause of a disease called “black mold” on certain fruits such as grapes, apricots, onions, etc.

Aspergillus niger on onion
Aspergillus niger on onion

Humans are exposed to the spores on a daily basis without any negative health effects and the fungus is considered GRAS—Generally Recognized as Safe. There have been cases where the fungus caused pneumonia, but this is usually in individuals with a weakened immune system or history of severe illness. Among horticultural workers however, the development of a serious lung disease called aspergillosis is a common occurrence due to repeated inhalation of peat dust.

In tropical areas, ear infections are frequently caused by Aspergillus niger. Although, the fungus is rarely the first causative agent, usually only causing infections when individuals were recently ill or treated with antibiotics. People with ear lacerations are also susceptible to infection by Aspergillus Niger, but treatment is simple and available.

What are Aspergillus Niger health effects?

As stated above, Aspergillus Niger has virtually no health effects (both positive and negative) on the average person, and most people can handle inhaling moderate amounts of spores. In fact, all of us are exposed to some airborne spores on a daily basis.

Only people with severe illnesses such as immune deficiency, HIV, and leukemia could be catastrophically affected by this fungus. Individuals who have severe mold allergies would also be affected by the fungus, causing reactions such as asthma and allergic alveolitis. It can even cause fungal balls to develop in the lungs of individuals exposed to it in large quantities.

An Aspergillus niger colony
An Aspergillus niger colony

While this is unusual, it could be disastrous if the wrong person is exposed to a large amount of these spores.

Where can Aspergillus Niger be found?

Aspergillus niger is highly thermotolerant — meaning it can survive in extreme conditions such as freezing weather or heat waves. In addition, this asexual saprophytic not picky when deciding what to contaminate, so it can be found almost anywhere.

While it contaminates especially decaying vegetation such as compost piles and dead leaves, it can be found in various other places. These include on stored grain, dried fruits and nuts, and even polyester-type polyurethanes. It’s an opportunistic fungus that will grow on anything if the conditions are favorable.

How to identify Aspergillus Niger in your home?

Like the name states, Aspergillus Niger is black in color but has a white layer beneath its surface. It’s frequently pinpointed as the source of black mold and is the most common mold concern in homes. In indoor environments it’s often found on damp walls and other surfaces. It can also be found in household dust and cereals, and other organic matter.

If you have a spot of mold but are not sure if it’s Aspergillus niger, calling a professional mold inspection company may be the best way forward. While Aspergillus Niger is considered safe, it can easily be confused with other darker types of mold and various Aspergillus species which are considerably more dangerous.

How to get rid of Aspergillus Niger?

General chemical and antifungal treatments are all adept at getting rid of Aspergillus Niger. Additionally, some home remedies include:

  • 70% alcohol. This is an effective treatment on walls and other surfaces because the alcohol penetrates the cells walls of the spores and effectively kills it. After applying the substance, leave it for 10 minutes and then wash the area with a clean rag or mop.
  • Phenols, like scrub soaps, mouth washes, and surface disinfectants will kill Aspergillus niger spores if left for 20 minutes after application. Once again, clean the area once the time is up.
  • Bleach. The hypochlorite found in household bleach will not only kill the mold, but also inhibit further growth.

While home remedies are usually effective, larger or deeper Aspergillus Niger infestations are best left for the mold removal professionals.