The nutritional value of mushrooms

The last decade has come with an increase in mushroom consumption due to a good content of protein, minerals and other nutritional substances. More than 2000 species exist in nature but only a number of approximately 22 species are intensely cultivated for commercial purposes. Apart from their well-known role in feeding animals and humans, they are also appreciated for their medical, nutraceutical and pharmaceutical benefits. Their use in the medical department is to be blamed on dietary fibers but mainly on chitin, a polysaccharide from the glucose family found in the exoskeleton of crustaceans and insects and beta glucans. The presence of specific bioactive compounds makes mushrooms therapeutically valuable for the immune system. They can prevent life threatening disease and work as cures for different illnesses. They are also known to exhibit antitumor, antiviral, antibacterial, hypotensive activities.

The carbohydrates in mushrooms are present in the form of monosaccharides, derivates, oligosaccharides, mannitol, trehalose. Trehalose is known for its potential to synthetize stress-responsive factors in human cells. Fungi rich in protein hold all the essential amino acids. They also have unsaturated fatty acids especially linoleic and oleic acids. Linoleic acid is famous for its anti-carcinogenic benefits on almost all stages of tumorigenesis and it reduces tumor growth by altering the 5-hydroxyeicosatetraenoic acid. It also contributes to mushroom flavor. The lipid fraction has antioxidant compounds like tocopherol. Regarding vitamins, they are rich in vitamin B complex and vitamin D. Under UV light, they produce D2 in great amounts. If we were to talk about minerals, mushrooms have proven themselves to be carriers for potassium, calcium, phosphorus and magnesium. Sodium is present in relatively small quantities making mushrooms suitable for hypertensive people’s diets. Mushrooms consumed fresh are known to lower the total cholesterol levels and support heart’s health. The presence of dietary fibers with non-dietary carbohydrates offers a wide range of health benefits.

Moreover, they are excellent functional and nutritional foods that contain selenium, ergothioneine, iron, etc. The bioavailability of any nutrient depends on the type of mushroom. They dry weight of ergothioneine varies between 0.2-2.0 mg/g. (king oyster, shiitake, oyster)

Their richness in dietary selenium contributes to their capability of reducing oxidative stress. Boletus edulis is said to have the highest concentration of selenium, 20 µg/g dry weight. Ergosterol under UV light exposure converts to vitamin D2. A study recorded the fact that UVB exposed mushrooms enhance mineralization and bone growth. Other nutrients like vitamin B12 present in fungi is quite similar to the one found in animal tissues making them perfect for a vegan’s diet. Dried mushroom powder like shiitake and oyster added in the daily diet is responsible for boosting the blood hemoglobin concentration and iron levels.

Mushroom nutraceuticals have been used since the ancient times for their medical benefits. Vitamin B is important for strengthening the nervous system, β-glucans empower the immune system and other minerals have antioxidant capacity. The polysaccharide content has well known antitumor, immunomodulatory and anti-inflammatory benefits. The antitumor activity is mediated through the thymus-dependent immune mechanism. A polysaccharide extracted from Agaricus bisporus exhibits a wonderful inhibiting action against human breast cancer. A novel heteropolysaccharide made form glucose units showed a great antitumor activity against HepG-2 cells. Proteins extracted from mushrooms are proved to have physiological activity in the gastrointestinal tract by enhancing nutrient absorption, inhibiting enzymes and modulating the immune system. Lecitins, ribonucleases and laccases have pharmaceutical attributes. Specific compounds also target free radical activity inhibiting the appearance of oxidative stress. Ganoderma lucidum, a mushroom used worldwide in therapy has more than 500 bioactive molecules like flavonoids, terpenoids, peptides and others. They are anti-diabetic, antioxidant, a free radical scavenger.

Researchers state that cooking methods used on mushrooms do not necessarily alter their nutritional benefits.

Due to the variety, availability and many cultivation methods, mushrooms emerge as the next generation’s source of nutritional food. They are considered to be a complete food suitable for the population thanks to their large amount of proteins, dietary fibers, vitamins and mineral contents. Along with their nutritional benefits they stand as strong candidates in the medical field and pharmaceutical industry. So, it’s fair to say that mushrooms should be taken into account by every researcher with the purpose of exploiting their many positive roles.

A report by Malina Puia

  1. Rathore, S. Prasad, S. Sharma, “Mushroom nutraceuticals for improved nutrition and better humanhealth: A review”, 2017
  2. Sharif, et al., “Wild Mushrooms: A Potential Source of Nutritional andAntioxidant Attributes with Acceptable Toxicity”, 2017
  3. Manzi,” Nutritional values of mushrooms widely consumed in Italy”, 2000
  4. A. Murugkar and G. Subbulakshmi, “Nutritional value of edible wild mushrooms collected from theKhasi hills of Meghalaya”, 2004
  5. J. Feeney, et al., “MushroomsVBiologically Distinct andNutritionally Unique”, 2014

On Common Oyster (Pleurotus ostreatus) yield

Mushrooms are a large group of fungi widely used for numerous benefits. They have anti-inflammatory benefits, rich nutritional values, anti-cancer properties, antioxidant qualities, etc. The oyster mushroom (Pleurotus sp.) is cultivated and consumed all over the world. People admire it for its unique taste, high nutritional value and health benefits. Pleurotus ostreatus became popular in Germany around 1917 and later it was discovered that several species can grow on agricultural wastes, lignocelluloses and forest-by products. There are many organic matters that can be cleverly used as substrates such as wheat straw, rice stalk and coco pet. However, the substrate porosity needs to be increased by adding gypsum. Usually, the substrate’s moisture should be kept around 60-75% and increased to 80-95% during fruiting.

One study used combinations of wheat straw and artichoke stalks for substrates. All mixtures were supplemented with 75g wheat brand and 30g of gypsum and afterwards moistened with 2,5 liters of water. The bags holding the different substrate mixtures were sterilized in an industrial autoclave for one and a half hour at 126 ºC under 1.5 A pressure. Prior to inoculation, they were allowed to cool. The growing room temperatures were between limits of 24-25 ºC. The relative humidity was set at 85%. The substrates used were three different mixtures of artichoke stalks and wheat straw, along with single wheat straw and single artichoke stalks. After performing different analyzes, the results indicated that the harvest time was highly different, shorter in artichoke stalks and artichoke stalks mixed with wheat straw than in wheat straw only (control lot). The highest yield was met when using 100% wheat straw. The best values for biological efficiency (66.41%) were also obtained with 100% wheat straw followed by a mix of 75% wheat stalks and 25% artichoke stalks with a value of 56.93%.

After gathering all the results, the conclusion was that regarding the biological efficiency, which is the most important parameter in mushroom growth, the highest and lowest values found in the experiment were 66.4% for 100% wheat stalk and 50.58% for 100% artichoke stalk. Therefore, artichoke stalk is a suitable candidate in the mushroom industry, but it is preferred to be used in mixtures for bringing its potential closer to the maximum.

Another experiment focused on using organic wastes, more precisely sawdust, cotton seed, wheat straw and paper waste to assess the production potential. The moisture content of the substrate had to be around 65 to 70%. Autoclave sterilization followed by several hours of cooling was mandatory before inoculating the spawn. Moreover, proper ventilation in the growth room was kept by occasionally opening the door. After the trial was done, mycelia growth was reported to be faster on cotton seed and paper wasted when compared to the other substrates. Also, pin-head formation took place rapidly in cotton seed. The time required by fruiting bodies to be matured enough varied from 27 days for cotton seed to 40.67 days for wheat straw. Records showed that product from paper waste knows a better growth in terms of thickness of the pileus and diameter. Furthermore, the number of fruiting bodies was higher in cotton seed than in other used substrates. The largest yield was harvested from cotton seed. The biological efficiency varied significantly. The highest percentage was present in cotton seed and the lowest in sawdust substrate. The conclusion from this study concerning oyster mushroom cultivation states that cotton seed and paper waste are suitable substrates.

Researchers in Taiwan compared three different substrates and combinations to study the effects, productivity, yield and biological efficiency. They used sawdust, corncob and sugar bagasse. All substrates were sterilized in an autoclave at 121ºC for 5h. The inoculated substrates were kept under dark conditions in an incubation room that provided a temperature of 28 ºC and 60-70 % relative humidity. This procedure was followed by a transfer to the cropping room where the humidity was increased to 90% and temperature was lowered to 24 ºC. After harvesting, the study showed a correlation between yield and biological efficiency. The substrate of 100% sawdust showed the lowest mushroom yield and the lowest biological efficiency. The highest values were recorded in 100% corncob (66.08%) and 100% sugar bagasse (65.65%). The differences can be blamed on the physical and chemical compositions of the substrates, pH, C/N ratio.

Higher biological efficiencies may be achieved trying different substrata and strains but still we need to look at several factors which in combination with a good strain could provide a biological efficiency of up to 200% which in some cases is known to occur for this mushroom. However, farm location remains an important point in getting higher mushroom crops and this needs to be analyzed by anyone wanting to grow oyster mushrooms for profit.

A report by Malina Puia

  1. A. Adebayo, J.K. Oloke, “OYSTER MUSHROOM (PLEUROTUS SPECIES); A NATURAL FUNCTIONAL FOOD”, 2017
  2. Girmay, et al., “Growth and yield performance of Pleurotusostreatus (Jacq. Fr.) Kumm (oyster mushroom) on different substrates”, 2016
  3. A. Nadir, “Effect of different substrates on the yield and quality of oyster mushroom (Pleurotusostreatus), 2014
  4. T. Hoa, et al., “The Effects of Different Substrates on the Growth,Yield, and Nutritional Composition of Two OysterMushrooms (Pleurotusostreatus and Pleurotuscystidiosus)”, 2015

On King Oyster (P. eryngii) yield

The King Oyster (Pleurotus eryngii) is a very popular edible mushroom in many countries due to its taste, nutritional richness and commercial potential. This mushroom just like many other mushrooms provides us with a great amount of vitamins and minerals among other nutrients. Oyster mushrooms are grown on many different substrates including agricultural wastes and industrial by-products. Mushroom cultivation is believed to be one of the most efficient and economically viable bio-technology. Their ability to grow in a wide range of temperatures makes them successful candidates for cultivation.

Researchers from Iran tried cultivating these edible mushrooms on different agricultural and lignocellulosic wastes like wheat straw and wood chips in order to obtain maximum yield and nutritional values. The substrates used were wheat straw, sawdust, sugar beet pulp, barley straw, maize stem and wood chips. All these six substrates were pasteurized by being soaked overnight followed by tissue softening at 212 F (100 ºC) for 1,5 h and finally drained. Substrates were supplemented with nitrogen sources. In general, studies claim that substrates supplemented with organic/inorganic substances often boost the production. Wood chips substrate supplemented with wheat bran showed an increased production. On the other hand, the low mushroom production gap on wheat straw could be blamed on the inability of Pleurotus eryngii to produce hydrolyzing enzymes for conversion to amino acids, nitrogen, and carbon.

This particular type of mushroom is successfully cultivated on many agro-industrial wastes. Some people use rice bran, wheat bran, poultry manure, brewers grain and cotton seed meal as organic supplements. In this case, the highest biological efficiency 73% was obtained with 20% dried brewers grain. An experiment from 2000 claimed to have achieved high yield when increasing supplementation of substrate with rice bran. 2007 was the year that brought different values in terms of biological efficiency, more precisely 73% when using mixtures of wheat straw – cotton straw, wheat straw and millet straw supplemented with 15% rice bran. The highest yield 23,3g/100g and 77,2% biological efficiency was obtained by using a blending of wheat straw and cotton straw with 20% rice bran supplement.

In Egypt, scientists used four different substrate growing media: sawdust, soybean straw, sugarcane bagasse and rice straw. Each medium substrate was then mixed with 5% calcium carbonate and wheat bran. The moisture content was adjusted to 69-71%. The mixture packed in bags was autoclaved at 121 ºC for 1h. The temperature of incubation was set at 25-27 ºC. At the end of incubation, the temperature was switched to 20 ºC. Out of all substrates tested, sawdust differed and recorded the shortest incubation period. On the opposite side, sugarcane bagasse recorded the longest incubation period with the peak being of 41 days. The yield ranged from 139-196, 145-192, 150-201 g/kg depending on the media substrate. Sawdust had the highest yield, 201 g/kg and sugar cane bagasse and rice straw recorded the lowest values. In terms of biological efficiency, sawdust took the first place with 65.22%, while sugarcane bagasse had the lowest value, 45.71%.

Comparatively, in 2008 a report registered highest yield values of 28g/100g on wheat straw – soybean straw (1:1). A similar work found the highest yield to be 25.6 g/kg on wheat straw – millet straw (1:1) + 10% rice bran and a biological efficiency of 85.2%. News in 2008 reported 23.2 g/kg yield and 77.2% biological efficiency in a mixture of wheat straw – cotton straw supplemented with 20% rice bran.

Another project was conducted in Iran highlighting two different substrates, sawdust and rice straw. Different strain of king oyster (Pleurotus eryngii) respond differently depending on the substrate used for cultivation, supplements and environmental factors. The temperature required for maximum prolificity and growth is between 12-17 ºC. Sterilization is called for 1h at 121 ºC under 1kg/cm2 pressure. Results concluded that on sawdust the highest yield was seen at strain Pe-1 (141 g), closely followed by strain Pe-2 (120.25 g). By comparison, for every strain cultivated on rice straw the values were lower than those cultivated on sawdust. Highest biological efficiency was met in the Pe-1 strain (73.5%), followed by Pe-2 (62.6%) on sawdust. Just like in the case of yield performance, biological efficiency in rice straw was lower than in sawdust.

In the end, the conclusion could be that differences of growth, yield performance and biological efficiency are due to the unique biological structure of every substrate and the physiology of each strain of Pleurotus eryngii that’s matching the right strain with your local climate conditions, the formulation of a good substrate recipe and a healthy methodology remain some of the most important factors that influence overall yield for this highly prized oyster mushroom type.

A report by Malina Puia

  1. R. H. Hassan, et al., “Cultvation of King Oyster Mushroom (Pleurotuseryngii) in Egypt”, 2010
  2. K. Jeznabadi, et al., “King oyster mushroom production using various sources of agricultural wastes in Iran”, 2016
  3. Moonmoon, et al., “Cultivation of different strains of king oyster mushroom(Pleurotuseryngii) on saw dust and rice straw in Bangladesh”, 2010

Growing Yellow Oyster on agro-waste

Pleurotus mushrooms are commercially important to the world market. They are widely cultivated and appreciated for their specific taste and nutritional values all over the world. They are rich in proteins, amino acids, and essential fatty acids.

Pleurotus citrinpileatus forms large clusters that bear a spicy-bitter-nutty flavor but unfortunately its fragility makes it difficult for post-harvest distribution to far away markets. This kind grows rapidly through pasteurized straw and sterilized sawdust. It develops well at higher temperatures than the common oyster mushroom. Will grow on logs and stumps, particularly of Ulmus and Carpinus. In China, farmers grow them on cottonseed hulls, sugar cane bagasse, sawdust, and straw. In the U.S.A., the most frequently used substrate compositions imply wheat straw or hardwood sawdust. For fruiting, substrates range from pasteurized wheat, chopped corn cobs to hardwood sawdust. Alternative substrates that are being developed commercially are represented by paper by-products, banana fronds and peanut hulls. Straw inoculated with grain spawn is considered to have considerably greater yields than straw inoculated with sawdust spawn.

Regarding to yield potentials it needs to be said that this species in not as prolific as the more popular Pleurotus ostreatus in the conversion of substrate. Studies have shown that using cottonseed amended substrates provided higher yield efficiencies. The biological efficiency ranges from 50-100% on wheat straw.

One study selected seven locally available substrates for figuring out the growth and yield performance: bean straw, sawdust of African mahogany, maize cobs, rice straw, wheat straw, sugarcane bagasse, and banana leaves. The best performance was obtain on bean straw substrate. In this particular study all seven substrates were pasteurized at 70°C for 2h. After cooling, they were individually spawned at a rate of 5% under laminar air flow and then, labeled and incubated in the dark at 25±2°C for 8-21 days. After completing this task, they were transferred into a humid growing room and kept at a 12 h light/ 12 h dark photoperiod at 23±2°C. After completing the experiment, data gathered concluded that all substrates recorded great fruiting and mycelia colonization. Maximum yield and biological efficiency (148%) was found at a spawn rate of 5% using bean straw substrate. Closely following was rice straw, with an efficiency of 90%, sugarcane bagasse 78%, wheat straw 41%, banana leaves 16% and the lowest, maize cobs 5%.

Another recent study focused on growing this type of mushroom on pea pod shell, paddy straw, brassica straw, radish leaves and cauliflower leaves separately and on various combinations. Pleurotus citrinopileatus apparently failed to grow on pea pod shells, radish and cauliflower leaves but developed very well on paddy straw in combination with other kinds of substrates. When harvested from paddy straw only, the total yield and biological efficiency was lower than on other wastes combined with paddy straw. The maximum biological efficiency was held by 70% paddy straw with 30% other wastes. Six essential amino acids were found in the mushrooms grown on the mixed substrate and also higher quantities of protein, sugar and non-reducing sugar.

It’s important to highlight the fact that using these agro-wastes gave high yields and definitely playing around with random substrate combinations or factors is key, but hey! once you got a great recipe a great strain and know what this particular strain likes and dislikes you’ll get happy results.

A report by Maina Puia

 

M.P. Singh, V. K. Singh, “YIELD PERFORMANCE AND NUTRITIONAL ANALYSIS OF PLEUROTUS CITRINOPILEATUS ON DIFFERENT AGROWASTES AND EGETABLE WASTES”, 2011.

Musieba, et al., “Suitability of Locally Available Substrates for Cultivation of the Kenyan Indigenous Golden Oyster Mushroom (Pleurotuscitrinopileatus Singer)”, 2012.

Paul Stamets, “Growing gourmet and medicinal mushrooms”, book 1993.

Plastic eating mushrooms

Even though the realm of fungi can help us make burial suits or edible lamps, I still remain the most impressed and hopeful at the prospect of us having packaging made of mycelium instead of petroleum. The fact that we could replace the unrecyclable Styrofoam with bio-degradable material definitely is good news for the ones who become depressed at the sight the unnecessary wrapping in supermarkets.  However, what do we do with the billions of tons of plastic that still float in our oceans or remain in our mounting landfills? Truth is there is still a lot of waste which is still polluting our environment and we have no idea how to get rid of it.

Luckily for us, the University of Utrecht is determined to experiment in every way possible with mushrooms and their fantastic possibilities. This time, they teamed up with Livin Studio, a collaborative design development office that gathers inventors, innovators, designers, culinary artists and scientist under the same roof. This project is called Fungi Mutarium and it aims to create a new fungi food product grown on plastic waste alongside building the apparatus to grow it.

The process starts with the plastic being UV treated in the “Activation Cylinder”, which is at the bottom of the mutarium. This step is necessary because the UV rays will sterilize the plastic and trigger the decomposition process of the material, thus making it easier for the fungus to break down. Then, the “FU”s are placed in the mutarium’s “Growth Sphere” with the help of some pincers for the work to be as sterile as possible. To explain, “FU” is the shape on which the fungus grows and it is made from agar – a seaweed based gelatin substitute. This is also mixed with starch and sugar, which both work as a nutrient base for the fungus. The fungi that they use are Schizophyllum commune and Pleurotus ostreatus that can be found anywhere in the world.

The shape of the FU was designed to hold the plastic but as well to offer enough space for the mushroom to grow. And because it is intended to be eaten by people, the Growth Sphere was made to resemble the harvesting mushrooms in the wild.

The plastic is then inserted in the FU to be digested and then the liquid nutrient solution in which there are fungi sprouts is dropped unto the FU’s to kindle the growing process. After a couple of weeks the plastic disappears and what is left is a FU which is edible due to the fact that the mushroom breaks down the plastic without storing it, like in the case of metals.

This experiment, doesn’t aim to digest all the plastic waste there is in the world, but rather to come up with a new technology to farm under extreme environmental conditions. However, it does prove that plastic can be broken down by fungi.

Another interesting fungus able to break down plastic is Pestalotiopsis microspora (found in the Amazon forest), an incredible fungus known also to break down styrofoam and plastic by-products.

 

A report by Ioana Popescu