RESEARCH STARTER

Rhizopus oryzae

Rhizopus oryzae is a filamentous fungus belonging to the family Rhizopodaceae and is commonly known for its pin-like appearance. Identified in 1895, this fungus is significant for its dual role in human health and industrial applications. While it can cause serious infections, particularly in immunocompromised individuals, accounting for about 70% of mucormycosis cases, it is also widely utilized in food production and biotechnology. R. oryzae is integral to the fermentation processes for foods like tempeh, enhancing their nutritional value and flavor, and it is recognized as safe by the U.S. FDA for food use.

In industry, R. oryzae is employed to produce valuable compounds such as lactic acid and ethanol, both of which are essential in various commercial applications, including food production and sustainable energy. This fungus can also facilitate the conversion of agricultural waste into new food sources, increasing the protein content of by-products. Its ability to thrive on a variety of organic substrates makes R. oryzae a versatile organism, contributing both to food security and the development of renewable resources.

Full Article

Rhizopus oryzae (also called R. oryzae or R. arrhizus) is a filamentous fungus in the family Mucoraceae (alternatively categorized under Rhizopodaceae) within the order Mucorales. Fungi in this order are commonly called “pin molds” because of their appearance, which resembles a long pin with a round head. Like other filamentous fungi, it secretes enzymes.

R. oryzae, which was first identified in 1895, can cause infections in humans and animals. It is responsible for about 70 percent of cases of mucormycosis, a rare fungal infection that can be fatal to individuals with reduced immunity. It is commonly found in the environment, and its spores can be inhaled, leading to sinus or lung problems. It can also infect injured skin. The Centers for Disease Control and Prevention (CDC) describes mucormycosis as a rare but serious infection that mainly affects immunocompromised people and people with uncontrolled diabetes; cases also increased sharply, notably in India, during the 2021 COVID-19 wave.

R. oryzae is commonly used in industry to produce cortisone and lactic acid, biosorption, and alcoholic fermentation; to treat wastewater; and to create biofuel. R. oryzae is one of several Rhizopus species used to create foods such as tempeh that are traditionally made in Asia.

Background

Fungi of the genus Rhizopus form rhizoids, which are branching filaments that grow downward and anchor the fungus in much the same way roots anchor plants in soil. Rhizoids release digestive enzymes and absorb digested organic substances. While found on a variety of organic matter, including fruits and soils, rhizoids primarily use glucose, a simple sugar, as their carbon source. They have also been found to use xylan, cellulose, sucrose, and other sugars as carbon sources. Urea is the preferred nitrogen source. R. oryzae is commonly used in solid-state fermentation (SSF), which uses culture substrates or bases that have low moisture levels.

Use of R. oryzae and other fungi in the fermentation of foods dates to about two thousand to three thousand years ago, when it was known in China as koji, meaning “moldy grains.” The practice of inoculating grain with mold traveled to Japan during the Yayoi period (300 BCE–300 CE). It is an important step in the fermentation process in Asia.

Koji can refer to both the mold and the grain it is growing on. The fungus consumes the starch in the grain to produce enzymes. Several types of fungi and wide varieties of grain are used to produce a variety of foods and beverages. For example, R. oryzae is one of the fungi used to make tempeh, a fermented food made of soybeans or cereal grains that originated in Indonesia. Some soybean-based fermentation, such as soybean sauce, uses a mixture of several fungi to develop a range of flavors and characteristics. Fermentation changes the available nutrients in soybeans by increasing the protein content, releasing vitamins, and developing antioxidants. Foods fermented with R. oryzae develop a velvety and juicy texture that many consumers prefer.

Industrial applications of R. oryzae developed after the discovery in 1936 that the fungus produced significant quantities of lactic acid from glucose. Its tolerance of a wide range of conditions and substrates meant that it could be readily used in industry. Two strains of R. oryzae have been identified and are divided by the primary organic acid they produce when grown on D-glucose, or dextrose. The first group produces L-(+)-lactic acid, while the second group produces a mixture of fumaric acid and L-(+)-lactic acid.

Overview

Fungi are capable of producing enzymes that degrade the cell walls of plants. Some enzymes also change the chemical composition of materials. Fermentation using fungi can make foods more digestible and increase the availability of proteins. R. oryzae is generally recognized as safe (GRAS) by the U.S. Food and Drug Administration and is often used in food production. It is one of the species used to make textured meat substitutes from substrates including beans and cereals; the texture is produced by the mycelium binding together particles.

Another application of the fungus is in developing new food sources from agricultural waste. Byproducts such as brewers’ spent grain (BSG) and waste such as stale bread can be converted to new edible products that provide significant protein. For example, Gmoser et al. found that the protein content of stale sourdough bread fermented with R. oryzae and Neurospora intermedia, another edible filamentous fungi, increased from 16.5 percent to 21.1 percent. The resulting product also contained greater quantities of essential amino acids, dietary fiber, and several nutrients. Combining the bread and some BSG-produced products with a more palatable texture, similar to commercial soybean burgers.

R. oryzae is able to use sugars from biomass to produce large quantities of ethanol, fumaric acid, and lactic acid, which are known as sustainable platform chemicals in industrial applications. Platform chemicals are necessary for making many chemicals and materials. The demand for ethanol has increased in the twenty-first century due to its many uses. It is used as an additive to automotive gasoline, a solvent, and an industrial chemical, for example. Fumaric acid is used in the food industry as a flavor enhancer, a preservative, and a pH adjustor. It can also be used in producing materials such as polyester. Lactic acid is added to foods, and animal feed is also used in manufacturing renewable plastics and other products.

Biodiesel is used as a clean energy source. Production has mostly used edible oils to create first-generation biodiesel. Governments and organizations have been moving away from using edible oils to make fuel for ethical reasons. Second- and third-generation biodiesels are produced using non-edible oils such as waste cooking oil and microbial oils, which contain high levels of free fatty acids (FFA). FFAs form soap in the process used in biodiesel plants, so they must be neutralized before the oils can be transformed. Researchers have been studying the use of R. oryzae to produce enzymes that efficiently neutralize FFAs in the production of second- and third-generation biodiesels. Researchers have also looked at the effects of fermentation on biomass, or organic material used as fuel, to find alternative transportation fuels. Because fungi such as R. oryzae can use multiple carbon sources, they could be useful in developing these fuels. Studies have examined R. oryzae for its ability to produce β-glucans from potato starch-processing wastewater and to develop antifungal compounds targeting Rhizopus proteins involved in virulence and host invasion.


Bibliography

Anchundia, Miguel, et al. “Polyphasic Identification of Rhizopus Oryzae and Evaluation of Physical Fermentation Parameters in Potato Starch Processing Liquid Waste for β-Glucan Production.” Scientific Reports, vol. 14, no. 14913, 2024, doi:10.1038/s41598-024-66000-5. Accessed 25 May 2026.

Cantabrana, Igor, et al. “Uses of Rhizopus Oryzae in the Kitchen.” International Journal of Gastronomy and Food Science, vol. 2, no. 2, Jan. 2015, pp. 103–11, doi:10.1016/j.ijgfs.2015.01.001. Accessed 25 May 2026.

“Clinical Overview of Mucormycosis.” Centers for Disease Control and Prevention, 24 Apr. 2024, www.cdc.gov/mucormycosis/hcp/clinical-overview/index.html. Accessed 25 May 2026.

“A Comprehensive In Vitro and In Silico Assessment of Eugenol Glycoconjugates against Resistant Rhizopus Isolates.” Molecular Biology Reports, 2025, doi:10.1007/s11033-025-10673-2. Accessed 25 May 2026.

Das, Ratul Kumar, et al. “A Fermentative Approach Towards Optimizing Directed Biosynthesis of Fumaric Acid by Rhizopus Oryzae 1526 Utilizing Apple Industry Waste Biomass.” Fungal Biology, vol. 119, no. 12, Dec. 2015, pp. 1279–90, doi:10.1016/j.funbio.2015.10.001. Accessed 25 May 2026.

Gmoser, Rebecca, et al. “From Stale Bread and Brewers Spent Grain to a New Food Source Using Edible Filamentous Fungi.” Bioengineered, vol. 11, no. 1, 24 May 2020, pp. 582–98, doi:10.1080/21655979.2020.1768694. Accessed 25 May 2026.

Londoño-Hernández, et al. “Rhizopus Oryzae—Ancient Microbial Resource with Importance in Modern Food Industry.” International Journal of Food Microbiology, vol. 257, 18 Sept. 2017, pp. 110–27, doi:10.1016/j.ijfoodmicro.2017.06.012. Accessed 25 May 2026.

López-Fernández, et al. “Second- and Third-Generation Biodiesel Production with Immobilised Recombinant Rhizopus Oryzae Lipase: Influence of the Support Substrate Acidity and Bioprocess Scale-Up.” Bioresource Technology, vol. 334, Aug. 2021, doi:10.1016/j.biortech.2021.125233. Accessed 25 May 2026.

Meussen, Bas J., et al. “Metabolic Engineering of Rhizopus Oryzae for the Production of Platform Chemicals.” Applied Microbiology and Biotechnology, vol. 94, no. 4, 2012, pp. 875–86, doi:10.1007/s00253-012-4033-0. Accessed 25 May 2026.

“Mucormycosis.” Centers for Disease Control and Prevention, 25 Feb. 2021, www.cdc.gov/mucormycosis/about/index.html. Accessed 25 May 2026.

“Mucormycosis.” World Health Organization, www.who.int/india/home/emergencies/coronavirus-disease-(covid-19)/mucormycosis. Accessed 25 May 2026.

Sabar, Muhammad Adnan, et al. “Degradation of Low Rank Coal by Rhizopus Oryzae Isolated from a Pakistani Coal Mine and Its Enhanced Releases of Organic Substances.” Fuel, vol. 253, Oct. 2019, pp. 257–65, doi:10.1016/j.fuel.2019.04.101. Accessed 25 May 2026.

“Secondary Direct Food Additives Permitted in Food for Human Consumption.” Electronic Code of Federal Regulations, U.S. Government Publishing Office, www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-173/subpart-B/section-173.130. Accessed 25 May 2026.

Spaeth, Sho. “Obsessed: A Man and His Mold.” Serious Eats, 13 June 2019, www.seriouseats.com/obsessed-koji-rich-shih. Accessed 25 May 2026.

Full Article

Rhizopus oryzae (also called R. oryzae or R. arrhizus) is a filamentous fungus in the family Mucoraceae (alternatively categorized under Rhizopodaceae) within the order Mucorales. Fungi in this order are commonly called “pin molds” because of their appearance, which resembles a long pin with a round head. Like other filamentous fungi, it secretes enzymes.

R. oryzae, which was first identified in 1895, can cause infections in humans and animals. It is responsible for about 70 percent of cases of mucormycosis, a rare fungal infection that can be fatal to individuals with reduced immunity. It is commonly found in the environment, and its spores can be inhaled, leading to sinus or lung problems. It can also infect injured skin. The Centers for Disease Control and Prevention (CDC) describes mucormycosis as a rare but serious infection that mainly affects immunocompromised people and people with uncontrolled diabetes; cases also increased sharply, notably in India, during the 2021 COVID-19 wave.

R. oryzae is commonly used in industry to produce cortisone and lactic acid, biosorption, and alcoholic fermentation; to treat wastewater; and to create biofuel. R. oryzae is one of several Rhizopus species used to create foods such as tempeh that are traditionally made in Asia.

Background

Fungi of the genus Rhizopus form rhizoids, which are branching filaments that grow downward and anchor the fungus in much the same way roots anchor plants in soil. Rhizoids release digestive enzymes and absorb digested organic substances. While found on a variety of organic matter, including fruits and soils, rhizoids primarily use glucose, a simple sugar, as their carbon source. They have also been found to use xylan, cellulose, sucrose, and other sugars as carbon sources. Urea is the preferred nitrogen source. R. oryzae is commonly used in solid-state fermentation (SSF), which uses culture substrates or bases that have low moisture levels.

Use of R. oryzae and other fungi in the fermentation of foods dates to about two thousand to three thousand years ago, when it was known in China as koji, meaning “moldy grains.” The practice of inoculating grain with mold traveled to Japan during the Yayoi period (300 BCE–300 CE). It is an important step in the fermentation process in Asia.

Koji can refer to both the mold and the grain it is growing on. The fungus consumes the starch in the grain to produce enzymes. Several types of fungi and wide varieties of grain are used to produce a variety of foods and beverages. For example, R. oryzae is one of the fungi used to make tempeh, a fermented food made of soybeans or cereal grains that originated in Indonesia. Some soybean-based fermentation, such as soybean sauce, uses a mixture of several fungi to develop a range of flavors and characteristics. Fermentation changes the available nutrients in soybeans by increasing the protein content, releasing vitamins, and developing antioxidants. Foods fermented with R. oryzae develop a velvety and juicy texture that many consumers prefer.

Industrial applications of R. oryzae developed after the discovery in 1936 that the fungus produced significant quantities of lactic acid from glucose. Its tolerance of a wide range of conditions and substrates meant that it could be readily used in industry. Two strains of R. oryzae have been identified and are divided by the primary organic acid they produce when grown on D-glucose, or dextrose. The first group produces L-(+)-lactic acid, while the second group produces a mixture of fumaric acid and L-(+)-lactic acid.

Overview

Fungi are capable of producing enzymes that degrade the cell walls of plants. Some enzymes also change the chemical composition of materials. Fermentation using fungi can make foods more digestible and increase the availability of proteins. R. oryzae is generally recognized as safe (GRAS) by the U.S. Food and Drug Administration and is often used in food production. It is one of the species used to make textured meat substitutes from substrates including beans and cereals; the texture is produced by the mycelium binding together particles.

Another application of the fungus is in developing new food sources from agricultural waste. Byproducts such as brewers’ spent grain (BSG) and waste such as stale bread can be converted to new edible products that provide significant protein. For example, Gmoser et al. found that the protein content of stale sourdough bread fermented with R. oryzae and Neurospora intermedia, another edible filamentous fungi, increased from 16.5 percent to 21.1 percent. The resulting product also contained greater quantities of essential amino acids, dietary fiber, and several nutrients. Combining the bread and some BSG-produced products with a more palatable texture, similar to commercial soybean burgers.

R. oryzae is able to use sugars from biomass to produce large quantities of ethanol, fumaric acid, and lactic acid, which are known as sustainable platform chemicals in industrial applications. Platform chemicals are necessary for making many chemicals and materials. The demand for ethanol has increased in the twenty-first century due to its many uses. It is used as an additive to automotive gasoline, a solvent, and an industrial chemical, for example. Fumaric acid is used in the food industry as a flavor enhancer, a preservative, and a pH adjustor. It can also be used in producing materials such as polyester. Lactic acid is added to foods, and animal feed is also used in manufacturing renewable plastics and other products.

Biodiesel is used as a clean energy source. Production has mostly used edible oils to create first-generation biodiesel. Governments and organizations have been moving away from using edible oils to make fuel for ethical reasons. Second- and third-generation biodiesels are produced using non-edible oils such as waste cooking oil and microbial oils, which contain high levels of free fatty acids (FFA). FFAs form soap in the process used in biodiesel plants, so they must be neutralized before the oils can be transformed. Researchers have been studying the use of R. oryzae to produce enzymes that efficiently neutralize FFAs in the production of second- and third-generation biodiesels. Researchers have also looked at the effects of fermentation on biomass, or organic material used as fuel, to find alternative transportation fuels. Because fungi such as R. oryzae can use multiple carbon sources, they could be useful in developing these fuels. Studies have examined R. oryzae for its ability to produce β-glucans from potato starch-processing wastewater and to develop antifungal compounds targeting Rhizopus proteins involved in virulence and host invasion.


Bibliography

Anchundia, Miguel, et al. “Polyphasic Identification of Rhizopus Oryzae and Evaluation of Physical Fermentation Parameters in Potato Starch Processing Liquid Waste for β-Glucan Production.” Scientific Reports, vol. 14, no. 14913, 2024, doi:10.1038/s41598-024-66000-5. Accessed 25 May 2026.

Cantabrana, Igor, et al. “Uses of Rhizopus Oryzae in the Kitchen.” International Journal of Gastronomy and Food Science, vol. 2, no. 2, Jan. 2015, pp. 103–11, doi:10.1016/j.ijgfs.2015.01.001. Accessed 25 May 2026.

“Clinical Overview of Mucormycosis.” Centers for Disease Control and Prevention, 24 Apr. 2024, www.cdc.gov/mucormycosis/hcp/clinical-overview/index.html. Accessed 25 May 2026.

“A Comprehensive In Vitro and In Silico Assessment of Eugenol Glycoconjugates against Resistant Rhizopus Isolates.” Molecular Biology Reports, 2025, doi:10.1007/s11033-025-10673-2. Accessed 25 May 2026.

Das, Ratul Kumar, et al. “A Fermentative Approach Towards Optimizing Directed Biosynthesis of Fumaric Acid by Rhizopus Oryzae 1526 Utilizing Apple Industry Waste Biomass.” Fungal Biology, vol. 119, no. 12, Dec. 2015, pp. 1279–90, doi:10.1016/j.funbio.2015.10.001. Accessed 25 May 2026.

Gmoser, Rebecca, et al. “From Stale Bread and Brewers Spent Grain to a New Food Source Using Edible Filamentous Fungi.” Bioengineered, vol. 11, no. 1, 24 May 2020, pp. 582–98, doi:10.1080/21655979.2020.1768694. Accessed 25 May 2026.

Londoño-Hernández, et al. “Rhizopus Oryzae—Ancient Microbial Resource with Importance in Modern Food Industry.” International Journal of Food Microbiology, vol. 257, 18 Sept. 2017, pp. 110–27, doi:10.1016/j.ijfoodmicro.2017.06.012. Accessed 25 May 2026.

López-Fernández, et al. “Second- and Third-Generation Biodiesel Production with Immobilised Recombinant Rhizopus Oryzae Lipase: Influence of the Support Substrate Acidity and Bioprocess Scale-Up.” Bioresource Technology, vol. 334, Aug. 2021, doi:10.1016/j.biortech.2021.125233. Accessed 25 May 2026.

Meussen, Bas J., et al. “Metabolic Engineering of Rhizopus Oryzae for the Production of Platform Chemicals.” Applied Microbiology and Biotechnology, vol. 94, no. 4, 2012, pp. 875–86, doi:10.1007/s00253-012-4033-0. Accessed 25 May 2026.

“Mucormycosis.” Centers for Disease Control and Prevention, 25 Feb. 2021, www.cdc.gov/mucormycosis/about/index.html. Accessed 25 May 2026.

“Mucormycosis.” World Health Organization, www.who.int/india/home/emergencies/coronavirus-disease-(covid-19)/mucormycosis. Accessed 25 May 2026.

Sabar, Muhammad Adnan, et al. “Degradation of Low Rank Coal by Rhizopus Oryzae Isolated from a Pakistani Coal Mine and Its Enhanced Releases of Organic Substances.” Fuel, vol. 253, Oct. 2019, pp. 257–65, doi:10.1016/j.fuel.2019.04.101. Accessed 25 May 2026.

“Secondary Direct Food Additives Permitted in Food for Human Consumption.” Electronic Code of Federal Regulations, U.S. Government Publishing Office, www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-173/subpart-B/section-173.130. Accessed 25 May 2026.

Spaeth, Sho. “Obsessed: A Man and His Mold.” Serious Eats, 13 June 2019, www.seriouseats.com/obsessed-koji-rich-shih. Accessed 25 May 2026.

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