''Rhizopus oligosporus'' is a

fungus A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from t ...

of the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

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 ...

and is a widely used starter culture 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, '' Rhiz ...

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 ...

, 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 Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...

several centuries ago. ''R. oligosporus'' is the preferred starter culture for tempeh production for several reasons. It grows effectively in the warm temperatures () which are typical of the Indonesian islands; it exhibits strong lipolytic 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 protease ...

activity, creating desirable properties in tempeh; and it produces

metabolites In biochemistry, a metabolite is an intermediate or end product of metabolism. The term is usually used for small molecules. Metabolites have various functions, including fuel, structure, signaling, stimulatory and inhibitory effects on enzymes, ...

that allows it to inhibit and thus outcompete other molds and

gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bact ...

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 Domestication is a sustained multi-generational relationship in which humans assume a significant degree of control over the reproduction and care of another group of organisms to secure a more predictable supply of resources from that group. A ...

form of '' Rhizopus microsporus'', resulting in a synonym of ''Rhizopus microsporus'' var. ''oligosporus''. ''R. microsporus'' produces several potentially toxic metabolites, rhizoxin and rhizonins A and B, but it appears the domestication and mutation of the ''R. oligosporus''

genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding g ...

has led to the loss of genetic material responsible for

toxin A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849 ...

production. The synonym is not currently recognized in fungal

taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

, 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 phylum, division or phylum of the kingdom Fungi. The members are now part of two Phylum, phyla: the Mucoromycota and Zoopagomycotina, Zoopagomycota. Approximately 1060 species are known. They are mostly t ...

, 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 ...

. ''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 Pathogenesis is the process by which a disease or disorder develops. It can include factors which contribute not only to the onset of the disease or disorder, but also to its progression and maintenance. The word comes from Greek πάθος ''pat ...

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 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 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, '' Rhiz ...

, 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 p ...

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 Lactobacillales are an order of gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped ( bacilli) or spherical ( cocci) bacteria that share common metabolic and physiological characteristics. These bact ...

, like ''

Lactococcus ''Lactococcus'' is a genus of lactic acid bacteria that were formerly included in the genus ''Streptococcus'' Group N1. They are known as homofermenters meaning that they produce a single product, lactic acid in this case, as the major or only pr ...

'' and ''Lb. casei''

species In biology, a species is the basic unit of 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 the appropriate s ...

, 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 In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...

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 In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...

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 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 mold. ...

Wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...

and

rice Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...

may be used.

Industrial use

This fungus has been used to treat waste and wastewater and produce industrial enzymes. This fungus can be grown for

phytase A phytase (''myo''-inositol hexakisphosphate phosphohydrolase) is any type of phosphatase enzyme that catalyzes the hydrolysis of phytic acid (myo-inositol hexakisphosphate) – an indigestible, organic form of phosphorus that is found in many p ...

, 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 natur ...

phytic acid.

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