''Rhizopus oligosporus'' is a fungus of the family

Mucoraceae The Mucoraceae are a family of fungi of the order Mucorales, characterized by having the thallus not segmented or ramified. Pathogenic genera include ''Absidia'', '' Apophysomyces'', ''Mucor'', '' Rhizomucor'', and ''Rhizopus''. According to a 2 ...

and is a widely used

starter culture A fermentation starter (called simply starter within the corresponding context, sometimes called a mother) is a preparation to assist the beginning of the fermentation process in preparation of various foods and alcoholic drinks. Food groups wh ...

for the production of

tempeh Tempeh or tempe (; jv, ꦠꦺꦩ꧀ꦥꦺ, témpé, ) is a traditional Indonesian food made from fermented soybeans. It is made by a natural culturing and controlled fermentation process that binds soybeans into a cake form. A fungus, '' Rhizo ...

at home and industrially. As the mold grows it produces fluffy, white

mycelia Mycelium (plural mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrates. A typical single spore germinates in ...

, binding the beans together to create an edible "cake" of partly

catabolized Catabolism () is the set of metabolic pathways that breaks down molecules into smaller units that are either oxidized to release energy or used in other anabolic reactions. Catabolism breaks down large molecules (such as polysaccharides, lipids, ...

soybeans. The domestication of the microbe is thought to have occurred in Indonesia several centuries ago. ''R. oligosporus'' is the preferred

for tempeh production for several reasons. It grows effectively in the warm temperatures () which are typical of the Indonesian islands; it exhibits strong

lipolytic Lipolysis is the metabolic pathway through which lipid triglycerides are hydrolyzed into a glycerol and free fatty acids. It is used to mobilize stored energy during fasting or exercise, and usually occurs in fat adipocytes. The most important r ...

and

proteolytic Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Uncatalysed, the hydrolysis of peptide bonds is extremely slow, taking hundreds of years. Proteolysis is typically catalysed by cellular enzymes called prote ...

activity, creating desirable properties in tempeh; and it produces metabolites that allows it to inhibit and thus outcompete other molds and gram-positive bacteria, including the potentially harmful ''

Aspergillus flavus ''Aspergillus flavus'' is a saprotrophic and pathogenic fungus with a cosmopolitan distribution. It is best known for its colonization of cereal grains, legumes, and tree nuts. Postharvest rot typically develops during harvest, storage, and/or ...

'' and '' Staphylococcus aureus''. ''R. oligosporus'' is at present considered to be a domesticated form of '' Rhizopus microsporus'', resulting in a synonym of ''Rhizopus microsporus'' var. ''oligosporus''. ''R. microsporus'' produces several potentially toxic metabolites,

rhizoxin Rhizoxin is an antimitotic agent with anti-tumor activity. It is isolated from a pathogenic plant fungus ('' Rhizopus microsporus'') which causes rice seedling blight. Biosynthesis Rhizoxin is biosynthesised by ''Burkholderia rhizoxinica'', a ...

and rhizonins A and B, but it appears the domestication and mutation of the ''R. oligosporus'' genome has led to the loss of genetic material responsible for toxin production. The synonym is not currently recognized in fungal taxonomy, so its current taxonomic position is best described as a member of the ''R. microsporus''

species group In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

Properties

''Rhizopus oligosporus'' is a fungus that belongs to the class

Zygomycetes Zygomycota, or zygote fungi, is a former division or phylum of the kingdom Fungi. The members are now part of two phyla: the Mucoromycota and Zoopagomycota. Approximately 1060 species are known. They are mostly terrestrial in habitat, living i ...

, which is one of two classes in the phylum

Zygomycota Zygomycota, or zygote fungi, is a former division or phylum of the kingdom Fungi. The members are now part of two phyla: the Mucoromycota and Zoopagomycota. Approximately 1060 species are known. They are mostly terrestrial in habitat, living i ...

. ''Rhizopus oligosporus'' belongs to the '' Rhizopus microsporus'' group. This

group A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic ide ...

is made of taxa with similar

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

that are associated with undesired metabolite production, pathogenesis and food fermentation. Although other varieties in ''Rhizopus microsporus'' may be harmful, ''Rhizopus oligosporus'' is not associated with production of potentially harmful metabolites. It is not found in nature and is frequently used by humans. ''Rhizopus oligosporus'' strains have a large diameter (up to 43 μm) and irregular spores with widely varying volume, (typically in the range 96–223 mm³). ''Rhizopus oligosporus'' has large, subglobose to globose spores, and high proportion irregular spores (>10 %). ''Rhizopus oligosporus'' also has spores with nonparallel valleys and ridges, and plateaus that sometimes are granular.

Metabolites

The fungus does not produce metabolites that are harmful to humans. Even after it is consumed, ''Rhizopus oligosporus'' produces an

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention ...

that limits gram-positive bacteria like '' Staphylococcus aureus'' and ''

Bacillus subtilis ''Bacillus subtilis'', known also as the hay bacillus or grass bacillus, is a Gram-positive, catalase-positive bacterium, found in soil and the gastrointestinal tract of ruminants, humans and marine sponges. As a member of the genus '' Bacillus ...

''. It also produces an

antifungal An antifungal medication, also known as an antimycotic medication, is a pharmaceutical fungicide or fungistatic used to treat and prevent mycosis such as athlete's foot, ringworm, candidiasis (thrush), serious systemic infections such as cryp ...

in the form of a

chitinase Chitinases (EC 3.2.1.14, chitodextrinase, 1,4-β-poly-N-acetylglucosaminidase, poly-β-glucosaminidase, β-1,4-poly-N-acetyl glucosamidinase, poly ,4-(N-acetyl-β-D-glucosaminide)glycanohydrolase, (1→4)-2-acetamido-2-deoxy-β-D-glucan glycano ...

protein.

Uses

Fermentation

Tempeh Tempeh or tempe (; jv, ꦠꦺꦩ꧀ꦥꦺ, témpé, ) is a traditional Indonesian food made from fermented soybeans. It is made by a natural culturing and controlled fermentation process that binds soybeans into a cake form. A fungus, '' Rhizo ...

, a popular Indonesian food, is created by

fermenting Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...

soybeans with ''Rhizopus oligosporus''. To create tempeh, soybeans first must be soaked in water (usually overnight) at a temperature similar to the environment in which it is placed. The soybean's outer covering is then removed, and the beans are partially cooked. Lactic acid bacteria, like '' Lactococcus'' and ''Lb. casei''

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

, play a major role in the fermentation of tempeh. For the tempeh to ferment, there needs to be a suitable, pure inoculum. Also needed are spores that germinate quickly. For the tempeh to attain its characteristic, compact, 'cake' form after fermentation, the soybeans become compressed by the

of ''Rhizopus oligosporus''. Rapidly growing mycelia help speed the growth of this fungus. Because mycelia are sensitive to dehydration and adverse temperatures, preserving tempeh for extended periods can be challenging. When the soybeans are bound together by the white mycelium, the fungus releases

enzymes Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. ...

that can digest protein. Many times, a good inoculum for this new fermentation comes from small pieces of old tempeh that have fermented. The fungus can ferment cereals and legumes other than soy, producing

oncom Oncom ( Aksara Sunda: ; IPA: ) is one of the traditional staple foods of West Java ( Sundanese) cuisine of Indonesia. There are two kinds of oncom: red oncom and black oncom. Oncom is closely related to tempeh; both are foods fermented using mol ...

. Wheat and rice may be used.

Industrial use

This fungus has been used to treat waste and wastewater and produce

industrial enzymes Industrial enzymes are enzymes that are commercially used in a variety of industries such as pharmaceuticals, chemical production, biofuels, food & beverage, and consumer products. Due to advancements in recent years, biocatalysis through isolated ...

. This fungus can be grown for phytase, an animal feed additive that breaks down the

antinutrient Antinutrients are natural or synthetic compounds that interfere with the absorption of nutrients. Nutrition studies focus on antinutrients commonly found in food sources and beverages. Antinutrients may take the form of drugs, chemicals that natura ...

phytic acid Phytic acid is a six-fold dihydrogenphosphate ester of inositol (specifically, of the ''myo'' isomer), also called inositol hexakisphosphate (IP6) or inositol polyphosphate. At physiological pH, the phosphates are partially ionized, resulting in ...

References

External links

Index Fungorum page (synonyms)''The Book of Tempeh: Professional Edition''
- by Shurtleff and Aoyagi (1979).
''Tempeh production: a craft and technical manual''
- By William Shurtleff, Akiko Aoyagi, Soyfoods Center (Lafayette, Calif.) {{Taxonbar, from=Q4911649 Mucoraceae Molds used in food production