 | This articleis missing information about phytase and feed use. Please expand the article to include this information. Further details may exist on thetalk page.(January 2021) |
| Rhizopus oligosporus | |
|---|---|
 | |
| White layer ofRhizopus oligosporus on homemadetempeh | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Fungi |
| Division: | Mucoromycota |
| Class: | Mucoromycetes |
| Order: | Mucorales |
| Family: | Mucoraceae |
| Genus: | Rhizopus |
| Species: | R. oligosporus |
| Binomial name | |
| Rhizopus oligosporus Saito | |
Rhizopus oligosporus is a fungus of thefamilyMucoraceae and is a widely usedstarter culture for the production oftempeh at home and industrially. As the mold grows it produces fluffy, whitemycelia, binding the beans together to create an edible "cake" of partlycatabolizedsoybeans. The domestication of the microbe is thought to have occurred inIndonesia several centuries ago.[1]
R. oligosporus is the preferredstarter culture for tempeh production for several reasons. It grows effectively in the warm temperatures (30–40 °C or 85–105 °F) which are typical of the Indonesian islands; it exhibits stronglipolytic andproteolytic activity, creating desirable properties in tempeh; and it producesmetabolites that allow it to inhibit and thus outcompete other molds andgram-positive bacteria, including the potentially harmfulAspergillus flavus andStaphylococcus aureus.[2][3]
R. oligosporus is at present considered to be adomesticated form ofRhizopus microsporus, resulting in a synonym ofRhizopus microsporus var.oligosporus.R. microsporus produces several potentially toxic metabolites,rhizoxin and rhizonins A and B, but it appears the domestication and mutation of theR. oligosporusgenome has led to the loss of genetic material responsible fortoxin production.[4] The synonym is not currently recognized in fungaltaxonomy, so its current taxonomic position is best described as a member of theR. microsporusspecies group.[5]
Rhizopus oligosporus is a fungus that belongs to the classMucoromycetes, which is one of two classes in thephylumMucoromycota.[6]Rhizopus oligosporus belongs to theRhizopus microsporus group. Thisgroup is made of taxa with similarmorphology that are associated with undesired metabolite production,pathogenesis and food fermentation. Although other varieties inRhizopus microsporus may be harmful,Rhizopus oligosporus is not associated with production of potentially harmful metabolites. It is a domesticated species and is only 'native' in human environs.[5]
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.[5]
The fungus does not produce metabolites that are harmful to humans.[5]
Even after it is consumed,Rhizopus oligosporus produces anantimicrobial peptide that limitsgram-positive bacteria likeStaphylococcus aureus andBacillus subtilis.[7] It also produces anantifungal in the form of achitinase protein.[8]
Tempeh, a popular Indonesian food, is created byfermentingsoybeans withRhizopus oligosporus.[9] 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, likeLactococcus andLb. caseispecies, play a major role in the fermentation of tempeh.[10] For the tempeh to ferment, there needs to be a suitable, pureinoculum. Also needed arespores that germinate quickly.[9] For the tempeh to attain its characteristic, compact, 'cake' form after fermentation, the soybeans become compressed by themycelia ofRhizopus oligosporus.[10] Rapidly growing mycelia help speed the growth of this fungus. Because mycelia are sensitive todehydration and adverse temperatures, preserving tempeh for extended periods can be challenging.[9] When the soybeans are bound together by the white mycelium, the fungus releasesenzymes that can digest protein. Many times, a good inoculum for this new fermentation comes from small pieces of old tempeh that have fermented.[9]
The fungus can ferment cereals and legumes other than soy, producingoncom. Wheat and rice may be used.[9][5]
This fungus has been used to treat waste and wastewater and produceindustrial enzymes.[4][5]
This fungus can be grown forphytase, an animal feed additive that breaks down theantinutrientphytic acid.[11]