Tag Archives: Student writing

Rhizopus oligosporus: The fungus that enhances plant-foods into tempeh

Posted on by

By: Elizabeth Gulick

Two handfuls of chanterelle mushrooms in a stir-fry; a delicious pizza topped with portabella fungi, and deep fried tempeh?! Edible fungus is vast, intriguing, and a nice source of nutrition for many animals, including us humans. Perhaps you have tried fried Tempeh strips or a tempeh-‘reuben’ sandwich from LeVoyeur in Olympia, WA? (yum!)

Tempeh is made from growing the fungus (aka mold/mould) Rhizopus oligosporus on soybeans or on other plant substrates like wheat, other grains, and beans. It is enjoyed worldwide for its edibility, unique flavor, and nutritional and medicinal qualities.

Tempeh’s appearance is peculiar; white fluffy mushroom mycelium enwraps the yellow soybeans (or whatever plant-food used) and holds it firmly together thus creating a flexible, bendable, and nicely chewy texture. It is most commonly sold in rectangular chunks about an inch thick. As it grows, the exposed surface develops some black and grey coloration, which is evidence of the fungus’ spores.

tempeh

This blog has beautiful pictures of preparing tempeh:

Tempeh originated in today’s Indonesia, where it is a staple source of protein. “Traditional tempeh is often produced in Indonesia using Hibiscus tiliaceus leaves. The undersides of the leaves are covered in downy hairs known technically as trichome

s to which the mold Rhizopus oligosporus can be found adhering to in the wild. Soybeans are pressed into the leaf, and stored. The earliest known reference to it appeared in 1815 in the Serat Centhini (Wikipedia).” Since then it has spread throughout the world picking up popularity among the poor and vegetarians because of its cheapness and nutritional value.

tempeh banana leaves

Tempeh being grown in Banana leaves (Wikipedia).

Tempeh is delicious, and! Some say when fried it tastes like fried chicken; I say it has an earthy taste. My favorite way to prepare Tempeh is to pan-fry strips of it in coconut oil until it is well done and then sprinkle nutritional yeast and salt on the fried bean-Fungi.  It is much firmer and flavorful than tofu.

Not only is Tempeh tasty, it has nutritional value as well. Tempeh made from soybeans is a fantastic source of protein. It is better than tofu because the soybeans have been pre-digested during the fermentation process. “The mycelium of R. oligosporus penetrates several layers into the soybean cotyledon. Mycelia colonize the intercellular material and solubize it by the activity of extracellular enzymes. Rhizopus spp. produce lipases, proteases, phytases and a variety of carbohydrateses (Boris Kovac & Peter Raspor, 1996).”

Tempeh is also better than tofu or cooked beans/grains because of the process of fermentation which it undergoes. “Many anti-nutritional factors can be found in unfermented legume seeds. During soaking and heating, and because of fungal enzymatic activity, almost all the anti-nutritious factors such as protease inhibitors, tannins, phytic acids, and lectins are removed” (Boris Kovac & Peter Raspor, 1996). Another scientific paper states, “The complex sugars stachyose and raffinose, which cause flatulence, are broken down into digestible sugars. During fermentation, the fungus produces the enzyme phytase that mobilizes the phytic acid improving bioavailability of minerals. Fermentation also promotes the synthesis of B group vitamins” (Ana Bavia, Carlos Silva, Maria Ferreira, Rodrigo Leite, Jose Mandarino, 2012).

Fermentation promotes B Vitamins? There is a special reason for this and it involves another microscopic friend: bacteria.  “During soaking (of the beans to be used), spontaneous fermentation by bacteria occurs.  Bacterial microflora , in which lactobacillus species are dominant, cause acidification of the beans and inhibition of some pathogenic bacteria. Although the mould increases the amount of physiologically active vitamins, the only source of vitamin B12 in tempeh products fermented by R. oligosporus are spoilage bacteria which appear during the soaking or fermentation of beans” (Boris Kovac & Peter Raspor, 1996). Bacteria and fungus, in the case of Tempeh, is a very nice pair!

incubating tempehTempeh incubating in plastic bags inside an oven.

Tempeh has medicinal qualities as well. “Some desirable effects on human health are obtained in Rhizopus oligosporus products. Reduction of the serum cholesterol level is obtained by a tempeh diet in rats.  The effect of decreasing cholesterol is presumably attributable to the lecithin, niacin, sitosterol and unsaturated fatty acids in tempeh.  Rhizopus oligosporus produces components with high antioxidative activity.  Nutritional rehabilitation of chronic diarhetic children with tempeh-milk based formula was evaluated. Recovery from diarrheal disease was reported to be faster with the tempeh based formula and resulted also in better weight gain, immunological values, and increase of hemoglobin (Boris Kovac & Peter Raspor, 1996).”

Rhizopus

Rhizopus micrograph

Tempeh is inexpensive and easy to culture at home. It takes about 24 hours to grow Rhizopus onto soybeans or other substrate. Traditionally it is grown wrapped up in banana leaves; in developed countries it is often grown in plastic bags with tiny pin holes punched in them to allow air flow (not too much air or the mould will produce spores too quickly). You can purchase spores and inoculate your substrate with them, or you can mix in remnants of previous batches of tempeh to inoculate the new substrate. The hardest obstacle is keeping the temperature during the time of incubation at a steady 85 to 90 degrees F. Another common mistake is having too much moisture in the beans; too much moisture during incubation can breed the wrong kinds of bacteria.

Rhizopus icon

Image from here.

Fermentation is a historic and a delicious act that has fed humanity for longer than we have had grocery stores. Whether you are a vegetarian, carnivore, or simply fungus friendly you can appreciate Tempeh for it’s inexpensive, quick, tasty, and nutritious qualities. Much like ruminants make vegetative proteins available to humans, the tempeh fungus transforms some grains economically and sustainably. Tempeh could become more and more popular as the world population continues to grow. More at-home tempeh production could ensure cheap localized protein sources worldwide.

References:

Alan Jurus. , & Walter Sundberg, (1976). Penetration of rhizopus oligosporus into soybeans in tempeh. Applied and Environmental Microbiology, 32(2), 284-287.

Ana Carla Furlan Bavia. , Carlos Eduardo da Silva, , Maria Pires Ferreira, , Rodrigo Santos Leite, , & Jose Marcos Gontijo Mandarino, (2012). Chemical composition of tempeh from soybean cultivars specially developed for human consumption. Science and Technology de Alimentos, 32(3), 613-620.

Boris Kovac. , & Peter Raspor, (1996). The use of the mould rhizopus oligosporus in food production. Food Technology, 35(1), 69-73.

Vikas Kumar. , Amit Sinha, , Harinder Makkar, , & Klaus Becker, (2010). Comparative effect of boiling and solid substrate fermentation using the tempeh fungus (rhizopus oligosporus) on the flatulence potential of african yambean (sphenostylis stenocarpa l.) seeds. Food Chemistry, 103(4), 945-959.

Wikipedia. “Rhizopus oligosporus” (http://en.wikipedia.org/wiki/Rhizopus_oligosporus)

Wikipedia. “Tempeh” (http://en.wikipedia.org/wiki/Tempeh)

William Scurtleff. , & Akiko Aoyagi, (1985). The history of tempeh: A fermented soyfood from indonesia by william schurtleff. Agricultural History, 59(4), 598-600.

Role of fungi in digestive systems of herbivores

Posted on by

By Corey Chin

Cow

Many people hear the word “fungi” and want to run the opposite direction – associating it with some nasty, toxic mess to stay far away from. I know because of the way people’s faces cringe to express their disgust when I tell them about the program I am enrolled in at my college titled “The Fungal Kingdom”. At this point I can just smile to myself knowing that there is so much these people don’t know about the fungi they are writing off as gross – that without them the world would look a whole lot different. Ever seen that cheesy film “A Day Without a Mexican” that shows how important immigrants from Mexico with actual work ethic are to this country, even though many complain about their presence? Well imagine what “A Day without Fungi” would look like – plants would die, delicious food sources would disappear, forest ecosystems would completely fall apart without any organisms capable of degrading wood, and many animals would have a much harder time digesting their food without the help of fungi in their gut – which is I’m going to talk about.

Chytridiomycota is a phylum of fungi that is widely dispersed globally, occurring in a diverse range of habitats “from the tropics to the arctic regions”. Chytrids can be found in aquatic systems, as plant parasites as well as vertebrate parasites like the infamous Batrachocytrium dendrobatidis responsible for the rapid decline of amphibian populations, but mostly occur in terrestrial habitats. The chytrid body – called the thallus – contains a sac-like structure called a sporangium that produces and stores zoospores (James et al., 2006). Zoospores can swim through aquatic environments using a posteriorly attached flagellum – similar to the sperm of a man that fertilizes an egg to impregnate a woman, zoospores are responsible for giving birth to new chytrids. Zoospores are capable of entering dormant states allowing them to stay alive in droughts and other harsh environments. There are five orders within the Chytridiomycota based on reproductive methods and the structure of zoospores. An especially interesting order, Neocallimastigales, occur as “anaerobic symbionts of the rumen” (James et al., 2006) as well as in intestines of other non-ruminant herbivores.

More often than not, when reading or learning about digestion in herbivores and specifically in ruminants, fungi are never mentioned – since mycology is a relatively new field of study, fungi are routinely left out of equations in which they are key players. As more and more people dive into the world of mycology, we are figuring out just how important fungi are, and finding them in places you might never think to look. All herbivores contain a spread of microflora in their gut to aid in their digestion, since high-fiber diets are very difficult to break down. Included in this gut microflora are the chytrids of Neocallimastigales. All herbivores ferment their food along their digestive tract. In ruminants – which include cows, sheep, goats, ox, deer, and more, fermentation takes place in the rumen – these animals are foregut fermenters, meaning their food is fermented before reaching the “true” stomach, allowing for more efficient digestion. To further explain, Merchen, Elizalde, and Drackly, 1997, write that “digestion by ruminants is the net result of a sequence of processes that occur in different segments of the gastrointestinal tract”. Primary fermentation of food takes place in the reticulo-rumen, then enzymes of host assist in acid hydrolysis and degreadation in the abomasums and small intestine, and lastly secondary fermentation is carried out in the cecum and large intestine (Merchen, et al., 1997).

Rumen

In order to understand digestion in ruminants it is essential to also understand the microbial communities within these digestion sites. Anaerobic fungi live in areas of the digestive tract to aid in fermentation in ruminants as well as in the gut of non-ruminant herbivores along with bacteria and other microflora.

It’s hard to imagine how microorganisms such as these chytrids were discovered within the gut of animals considering they are tiny creatures living inside long, slimy, complex digestive tracts of select animals. DNA sequences were taken from feces of wild and domestic herbivores using a process called polymerase chain reaction to amplify specific gene strands. Through this sequencing, six genera were found within the Neocallimastigales – Neocallimastix, Piromyces, Orpinomyces, Anaeromyces, Caecomyces, and Cyllamyces – the most recently described genus (Nicholson, McSweeny, Mackie, Brookman, Theodorou, 2010). Species within Neocallimastigales have even been found in landfill sites, further enforcing their role as cellulose degraders (Lockhart et al., 2006). Without this technology it would be impossible to isolate these organisms or phylogenetically relate them to each other and other groups of fungi.

So we know that fungi are present in the gut of herbivores, but how do they actually help the animal? Like all members of Chytridiomycota, chytrids within the Neocallimastigales order reproduce asexually through motile zoospores with flagella, as mentioned earlier. These zoospores allow for “rapid colonisation of freshly ingested plant material” (p. 66 Nicholson et al., 2010) that enter the digestive tract of herbivores. The fungi then excrete fibrolytic enzymes – including cellulases, hemicellulases, proteases, and esterases, to help break down the plant material into three fatty acids – acetic acid, proprionic acid, and butyric acid – which are then used by the animal for energy. Don’t forget that bacteria and some protozoa are also important for this process!

So the next time you see some mold on your tangerine or are served some mushrooms you might think of as dirty and unappealing, remember how diverse fungi are and the key roles they serve in not only ecosystems around the world, but even in the digestive systems of many animals we know and love!

References

Brookman, J., Mackie, R., Mcsweeny, C., Nicholson, M., Theodorou, M. (2010). Diversity of anaerobic gut fungal populations analysed using ribosomal ITS1 sequences in faeces of wild and domesticated herbivores. ScienceDirect, Volume 16, issue 2. Retrieved from http://www.sciencedirect.com.bay.evergreen.edu/science/article/pii/S1075996409000833

James, T., Griffith, G., Letcher, P., Longcore, J., Mozley-Standridge, S., Porter, D., Powell, M, Vilgalys, R. (2006). A molecular phylogeny of flagellated fungi (Chtridiomycota) and description of a new phylum (Blastocladiomycota). Mycologia, 98. Retrieved from http://www.mycologia.org/content/98/6/860.full

Lockhart, R., Van Dyke, M., Beadle, I., Humphreys, P., McCarthy, A. (2006). Molecular Biological Detection of Anaerobic Gut Fungi from Landfill Sites. Applied and Environmental Microbiology, 72. Retrieved from http://aem.asm.org/content/72/8/5659.full

Merchen, N. R., Elizalde, J. C., Drackley, J. K., (1997). Journal of Animal Science. Current perspective on assessing site of digestion in ruminants, 75, 2223-2234.

 

Healthful, helpful Hericium

Posted on by

Photo by Diane Cavallero (rogersmushrooms.com)

By Brian Matson

The genus Hericium has several conspicuous species in the forests of North America, often hanging high up in the branches just out of reach or on the ground on dead logs. These saprophytic (wood-eating) mushrooms look unlike any other Basidiomycetes that you might see, lacking the cap and gill features so common to this phylum.  What they are missing in commonality they make up for in beauty. Often weighing several pounds with an untarnished creamy white coloration make these fungi a treat worth looking for. Not only are they unique in appearance they are edible and choice, having a unique taste, they also show promising health benefits such as tumor reduction and stimulating the production of nerve growth factor (“Hericium: The Nerve Regenerators @ Mushrooms For Health,” n.d.).

There are four species of Hericium present in North America. Hericium erinaceus and Hericium abietis can be found in our Pacific Northwest and as far south as California on conifer wood. Hericium coralloides which is wide spread and grows on conifers , and Hericium americanum  which can be found in the Great Plains growing on hardwoods. All four of these species have stalactite-appearing teeth that hang off off the fruiting body. They are an easy fungus to identify for beginner mycologists because there are no poisonous look-a-likes in North America. David Arora describes these fungi as having a similar flavor and texture to fish or lobster. It can be sautéed, marinated, grilled, or prepared in almost any fashion, making it a very flexible mushroom for cooking. My preferred method is to dry sauté the mushroom until the liquid has evaporated off, then adding 1-2 tbsp of avocado oil, frying until browned, and then sprinkling on a little salt.  Patience is the key while cooking, because it often takes longer than you will want to wait. The wait is worth the euphoria trying this delicacy!
Hericium has been used as a traditional medicine in China and Japan for many years; but its medicinal uses are still being explored in western medicine (“Hericium: The Nerve Regenerators @ Mushrooms For Health,” n.d.) .  The fungi in the genus Hericium all contain compounds called erinacines.  Erinacines have shown the ability to stimulate the production of nerve growth factor in animal trials (“Hericium: The Nerve Regenerators @ Mushrooms For Health,” n.d.) , and show much potential in the treatment of debilitating diseases that affect nerve health or function.  In a double-blind placebo controlled study that took place in Japan in 2008, participants whose ages ranged from 50-80 were given orally powdered Hericium erinaceus and their cognitive function was monitored.  All 14 test subjects given the powdered Hericium erinaceus showed improved cognitive function when compared to 5 of the 15 placebo participants (Mori, Inatomi, Ouchi, Azumi, & Tuchida, 2009) .  The studies show promise in the effectiveness of Hericium in treatment of neurological diseases.  More studies are being done testing the effectiveness as a tumor suppressant, and while there has been less testing done in this area the few tests there have been show promise.

Works Cited
Plants & Fungi: Hericium erinaceus (bearded tooth) – Species profile from Kew. (n.d.). Retrieved February 9, 2014, from http://www.kew.org/plants-fungi/Hericium-erinaceus.htm

Hericium – Wikipedia, the free encyclopedia. (n.d.). Retrieved February 9, 2014, from http://en.wikipedia.org/wiki/Hericium

Hericium: The Nerve Regenerators @ Mushrooms For Health. (n.d.). Retrieved February 9, 2014, from http://mushrooms4health.com/hericium-the-nerve-regenerators/

The Genus Hericium (MushroomExpert.Com). (n.d.). Retrieved February 9, 2014, fromhttp://www.mushroomexpert.com/hericium.html

Mori, K., Inatomi, S., Ouchi, K., Azumi, Y., & Tuchida, T. (2009). Improving effects of the mushroom Yamabushitake ( Hericium erinaceus ) on mild cognitive impairment: a double-blind placebo-controlled clinical trial. Phytotherapy Research, 23(3), 367–372. doi:10.1002/ptr.2634

Yurchenco, J. A., & Warren, G. H. (1961). A Laboratory Procedure for the Cultivation and Fructification of Species of Hericium. Mycologia, 53(6), 566–574. doi:10.2307/3756458