Rhizopus microsporus var. Oligosporus

from Wikipedia, the free encyclopedia
Rhizopus microsporus var. Oligosporus
Rhizopus oligosporus on homemade tempeh

Rhizopus oligosporus on homemade tempeh

Systematics
Subdivision : Mucoromycotina
Order : Mucorales
Family : Mucoraceae
Genre : Rhizopus
Type : Rhizopus microsporus
Variety : Rhizopus microsporus var. Oligosporus
Scientific name
Rhizopus microsporus var. Oligosporus
( Saito ) Schipper & Stalpers

Rhizopus microsporus var. Oligosporus , often known by its synonym Rhizopus oligosporus , is a mushroom of the Mucoraceae family, it is used as a culture for preparing tempeh at home and on an industrial scale. In the course of its growth, Rh. Oligosporus producescotton wool-like, white mycelia , which grow around the beans or seeds rich in starch and protein and thus form an edible, cut-resistant loaf. It is believed that Rh. Oligosporus wascultivatedin Indonesia centuries ago.

Rhizopus oligosporus is the preferred starter culture for tempeh for several reasons . The fungus not only grows most efficiently at temperatures typical for the Indonesian islands (30–40 ° C), it also has pronounced lipolytic and proteolytic properties that have a positive effect on the quality of the tempeh. In addition, the fungus produces active substances that curb the growth of gram-positive bacteria such as the potentially dangerous Staphylococcus aureus but also the Aspergillus flavus .

It is currently assumed that Rhizopus oligosporus is a cultivated variant of Rhizopus microsporus . Its correct, full name is therefore Rhizopus microsporus var. Oligosporus . However, Rh. Microsporus produces a multitude of toxic metabolic products, rhizoxin as well as rhizonin A and B. The genetic facilities for the production of these toxins have been lost in the course of cultivation to Rhizopus oligosporus .

properties

Rhizopus oligosporus belongs to the order of the Mucorales and to the group Rhizopus microsporus . This group includes species which are used in the fermentation of food and which are partially characterized by undesirable metabolic products or are considered pathogens. However, the cultivated variant Rhizopus oligosporus does not show any of these negative properties and can therefore be used in food production without hesitation. Rhizopus oligosporus does not occur wild in nature and is an important cultivated mushroom.

Compared to other Rhizopus species, the fungus has a relatively high proportion of 10 to 30% (depending on the cultivated line examined) of irregularly shaped and then particularly long spores with a length of up to 43 µm and a volume of up to 96–223 µm³. Regularly shaped spores are more or less spherical in shape. Statistical evaluations, taking into account all spore shapes, resulted in mean widths of 5.2 to 6.5 µm and mean lengths of 6.6 to 8.9 µm (depending on the examined culture line), which were above the mean dimensions of other examined Rhizopus species. With regard to their surface texture, the spores have intersecting furrows and ribs as well as plateaus, which sometimes have a grainy structure. These characteristics also distinguish them from spores of certain other Rhizopus species, which is a starting point for assumptions about evolutionary relationships or domestication lines to Rh. Oligosporus .

Tempeh fermentation

The popular Indonesian food tempeh is produced with the help of Rhizopus oligosporus . Due to its very high protein content and mild taste, tempeh can be used in many dishes after preparation. With more than 40% protein, it is often used as a meat substitute. Tempeh can be added to soups or seasoned in slices and cubes.

To make tempeh, soybeans are soaked in water (usually overnight) at ambient temperature. The husks of the soybeans are then removed and the beans are then partially or fully cooked.

Lactic acid bacteria , such as species of Lactococcus and Lb. casei , play a large role during fermentation . A pure starter culture from Rhizopus oligosporus , which is added after the soybeans have been cooled to around 30 ° C, is also essential for clean and effective fermentation in order to ensure optimal growth conditions. In order for the tempeh to take on the characteristic shape of a rectangular bar or loaf and to be cut-proof, light pressure must be applied to the mixture of cooked soybeans and starter culture. Molds are often used to better portion the end result, traditionally the mixture is wrapped in banana leaves. The use of molds also improves the climate for the ferment , as they protect it from drying out and foreign spores. Protected in this way, the ferment can also keep the temperature better, which has a positive effect on the speed of growth and is important for a single-variety culture of Rhizopus oligosporus .

Due to the high water content and sensitivity to temperature fluctuations, the shelf life of tempeh, in untreated form and unpacked, is limited.

In the course of fermentation, Rhizopus oligosporus releases enzymes that make the very protein-rich product even more digestible and better tolerated.

Tempeh-like products can also be made from other raw materials such as wheat and rice. For the further cultivation and production of fresh tempeh, small pieces of already fermented tempeh can be used.

Other uses

Rhizopus oligosporus can be used for the organic treatment of waste and wastewater and is used for industrial enzyme production.

See also

Individual evidence

  1. ↑ Shurtleff, W. & Aoyagi, A. 2001. The book of tempeh. 2 2nd Ten Speed ​​Press. Berkeley, California pp.
  2. ↑ MJR Nout: Effect of Rhizopus and Neurospora spp. on growth of Aspergillus flavus and A. parasiticus and accumulation of aflatoxin B1 in groundnut . In: Mycological Research . 93, 1989, pp. 518-523. doi : 10.1016 / s0953-7562 (89) 80046-2 .
  3. ↑ Sin-ya Kobayasi, OKAZAKI Naoto, KosEKI Takuya: Purification and Characterization of an Antibiotic Substance Produced from Rhizopus oligosporus IFO 8631 . In: Biosci. Biotechnol. Biochem. . 56, No. 1, 1992, pp. 94-98. doi : 10.1271 / bbb.56.94 . PMID 1368137 .
  4. ↑ J. Jennessen, KF Nielsen, J. Houbraken, EK Lyhne, J. Schnürer, JC Frisvad, RA Samson: Secondary metabolite and mycotoxin production by the Rhizopus microsporus group . In: Journal of Agricultural and Food Chemistry . 53, 2005, pp. 1833-1840. doi : 10.1021 / jf048147n . PMID 15740082 .
  5. ↑ Rhizopus - an overview | ScienceDirect Topics. Retrieved January 29, 2019 .
  6. ↑ a b c Jennifer Jennessen, Johan Schnürer, Robert A. Samson, Jan Dijksterhuis: Morphological characteristics of sporangiospores of the tempe fungus Rhizopus oligosporus differentiate it from other taxa of the R. microscopus group . In: Mycological Research . 112, 2008, pp. 547-562. doi : 10.1016 / j.mycres.2007.11.006 . PMID 18400482 .
  7. ↑ a b c W Hessel Tine, EW Swain, Hwa L. Wang: Mass production of Rhizopus oligosporus spores and their application in tempeh fermentation . In: Journal of Food Science . 40, 1940, pp. 168-170. doi : 10.1111 / j.1365-2621.1975.tb03762.x . Retrieved May 29, 2014.
  8. ↑ a b Elizabeth Caplice, Gerald F Fitzgerald: Food fermentations: role of microorganisms in food production and preservation . In: International Journal of Food Microbiology . tape 50 , no. 1 , September 15, 1999, ISSN  0168-1605 , p. 131–149 , doi : 10.1016 / S0168-1605 (99) 00082-3 ( sciencedirect.com [accessed January 29, 2019]).

Web links