Introduction

Fungi are the essential organisms for the recycling of organic waste and efficiently return the nutrients to the environment. Mushrooms are macro-fungi which are now-a-days more popular for remediation purpose because apart of bioremediation it also provide mycelium or fruiting bodies as a protein source. They do not contain chlorophyll and are non-green organisms (Ukwuru, 2018). The nutrient content of the mushroom can be change based on different substrates on which the mushroom is cultivated (Subramanian, 2014). These organisms have diversified group which are belonging to basidiomycetes and ascomycetes that can be edible and non-edible. 

Pleurotus species are saprophytic because their tissues contain no chlorophyll for carbohydrate synthesis. Mushrooms consist of cap, gills stalk or stipe, spores, ring, vulvas and mycelium.Pleurotus sp. is popularlycalled as oyster mushroom. It is also known as ‘Dhingri’ in India. This genus includes about 40 species that are popularly known as to as “oyster mushrooms”. According to Jayakumar and Thomas (2011) oyster mushroom is reported to consists of amino acids like other edible mushrooms, such Agaricus bisporus and Lentinus edodes . pleurotus species generally grown in natural habitat on waste rich in lignocelluloses (Mahalakshmi, 2019).                        

Oyster mushrooms are naturally grown on decayed material and are famous for appropriate to its taste, medicinal and nutritional aspects. It is a simple cultivation technique requires not so skilled personnel and is cost effective. Cultivation of P. ostreatus is a best alternative for edible mushroom production as compared to other species of mushrooms for unskilled farmers than other mushrooms species (Mbassi et al., 2018).Mushroom cultivation technology can play a significant role in the management of agro and organic wastes. These wastes can be recycled into food products and help in defeating in malnutrition problem in developing countries. Edible mushrooms contain high protein contents, minerals, low fat and vitamins such as vit. B, D, K, A and C (Jawad et al. 2013). Theoptimum temperaturefor cultivation of this species (15-30 .Temperature varies from species to species (Mahalakshmi, 2019). Pleurotus mushroom has about 40 well-recognized species, out of which 25 species are commercially cultivated all over the world. They are P. sapidus, P. fossulatus, P. eryngii, P. ostreatus, P. djamor, P. opuntiae,  P. cystidiosus, P. tuber-regium,  P. australis, P. populinus, P. sajor-caju, P. flabellatus, P. florida,  P. columbines and P. membranaceus (Suman and Sharma, 2007). According to Ahmed (2009) Pleurotus species efficiently degrading lignin agent and can grow on several lignocellulosic materials. Consequently, mushroom cultivation technology is very simple and low cost production technology, which gives consistent growth with high biological efficiency. Pleurotus species can grow well in fixed range oftemperature conditions; hence suitable for cultivation all through the seasons in various regions of tropical countries.

The bioconversion of agricultural residues into food has attracted the world attention in recent years. The cultivation of edible mushrooms has a great potential for the production of protein rich quality food and for recycling of cellulosic agro-residues and other wastes and serves as the most proficient and economically feasible technology for the bioconversion of lignocellulosic organic waste materials to high quality food. They can easily grow on almost all types of cellulosic residues such as banana leaves, dried paddy straws, cotton waste and rice straws sawdust enriched with poultry droppings Jatropha and even invasive weed species (Fahad, 2015). Poonkodi (2015) studied that naturally growing mushrooms are mostly poisonous. They bear attractive colours and contain terpenoid, 1, 4-dialdehyde group, which is very much essential for organisms such as antibiotics, antifeedant activities, mutagenicity, and cytotoxicity etc. But, edible mushrooms do not have such kind of attractive colours. So, in comparison with natural mushrooms, artificially cultivated mushrooms are good for consuming.

Mushrooms are economically important biotechnological products, and a good source of protein, vitamins, minerals, and biotechnologically active substances (Liu, 2018). It having a delicacy and palatable nature makes to be considered as vegetarian chicken. Besides their excellent flavor mushrooms have attracted much attention due to their proven healthy properties (Chiron and Michelot, 2005). This are abundant in protein and vitamins and is low calorie food and thus are suggested for heart and diabetic patients. They are rich in protein, as compared to cereals, fruits and vegetables. In addition to protein (3.7%), they also contain carbohydrate (2.4%), fat (0.4%), minerals (0.6%), and water (91%), on fresh weight basis. It is also rich in vitamin B C, D, A and K, which are retained even after cooking. Since mushrooms possess low caloric value, high protein, fiber content and high K: Na ratio, they are ideally suited for diabetic and hypertension patients. They are also reported to possess anticancer activities (Patil, 2010).

In addition, most of the species also contains a variety of compounds that are biologically active in nature showing such biolocical activities as antioxidant, antidiabetic, anticancer etc. (Zhang, 2019). Various species of mushroom has been traditionally used for medicinal purpose and treatment of diseases (Jayakumar, 2011).

Macro nutrients content of Pleurotus ostreatus.

 Several researches from all over the world recommended that the Pleurotus mushroom are high in nutritional content and various bioactive compounds such as terpenoids, phenols, alkaloids, steroids and lectins with promising biological effects (Krishnamoorthy and Sankaran 2014). P. ostreatus has greater contents of iron, copper, potassium, phosphorus, magnesium and zinc, and the stipes contains with sodium (Mbassi et al. 2018) (fig. 1). Mushrooms have the ability to accumulate mineral elements from different cultivation substrates. It is an excellent dietary food product (Kinge, 2016).

1. Phosphorus

Phosphorus works with calcium to help build bones. We need the right amount of both calcium and phosphorus for bone health 80% of phosphorus is associated with calcium to form bones and teeth. Phosphorus also plays an important structural role in nucleic acid and cell membranes and it’s involved in the body’s energy production (Mbassiet al. 2018). Phosphorus was found the most abundants mineral element in the cultivated mushroom (Victor and Olatomiwa, 2013) studied.

Fig.1Bioactive compinds of mushroom and its application.

2. Potassium

Potassium is the third most abundant mineral in the body it helps the body regulate fluid, send nerve signals and regulate muscle contractions. Roughly 98% of the potassium in our body is found in our cells. Of this, 80% is found in our muscle cells, while the other 20% can be found in our bones, liver and red blood cells. Potassium is found in most concentrated form various species of edible mushrooms (Mbassi et al. 2018) harvested from hardwood (A. leiocarpus) sawdust and softwood sawdust respectively. This study demonstrated that potassium supplementation lowered systolic blood pressure an average of 12 mm Hg and diastolic blood pressure an average of mm Hg.

3. Calcium

Calcium is very essential in muscle contraction, oocyte activation, building strong bones, teeth, blood clotting, nerve impulse transmission, regulating heart and fluid balance within cells (Pisteet al. 2015).

4. Sodium

Sodium is both an electrolyte and mineral that helps maintain the balance of water in and around our cells. It’s important for proper muscle and nerve function. It also helps maintain stable blood pressure levels.P. ostreatus harvested from cupuacuexocarp supplemented with rice bran. Normally sodium level should be between 135 and 145 mEq/L. Hyponatremia occurs when our sodium level goes below135 mEq/L.

5. Magnesium

Magnesium is the fourth most abundant mineral in the human body. About 60% of the magnesium in body is found in bone, while the rest is in muscles, soft tissue and fluids including blood. Magnesium was found least in this species. About 1.25mg /100g was obtained from the P. ostreatus. harvested from hardwood sawdust while 1.04 mg/100g was obtained from softwood.

Table: 1 Nutritive value of oyster mushroom (USDA National Nutrient data base)

3. Micro nutrient content of P. ostreatus

Mushrooms are known for excellent biological accumulators of minerals. Iron, copper, zinc, manganese and selenium etc. falls under minor/trace elements. Zinc was found in high amount in L. edodes species.  Copper and manganese are found in low concentration. As well as selenium is also present in mushroom and is known as anticancer. Nickel, Lead and cadmium in mushroom is below detection levels. The presence and allocation of some minerals cause toxicity in a variety of mushrooms.  Mercury, cadmium and copper are accumulated in fruiting bodies through its surrounding nature; levels of zinc and manganese are comparable in the fruiting body and in the relevant substrate, while concentrations of lead and iron are lower in the fruiting body than in the other substrate (Mallikaarjuna, 2012).

Bioactive compounds in P. ostreatus

P. ostreatusis most cultivated after button mushroom for throughout world. On the basis of nutrition, it is known as good low caloric food rich in protein, carbohydrates, fiber, minerals etc. (Krishnamoorthy and Sankaran, 2014).

1. Protein Content

Mushrooms are rich source of proteins.Itis recognized as a potential source of new proteins such as lectins, enzymes, proteases inhibitor and hydrophobins (Krishnamoorthy and Sankaran, 2014). In mushrooms, protein content is dependent of substrate nature. Victor and Olatomiwa (2013) reported that Pleurotus samples produced on Pycnanthusongoleubis, Ceibapentandra, Cananiumsp. sawdust in which the protein composition ranges between 20.03 to 20.11%.

2. Crude Fiber Content

Mushrooms are abundant in dietary fibers. According to Mbassiet al. (2018) reported that crude fiber content depends on the cultivated substrate. Specifically, they obtained crude fiber content from produced mushroom with cottonseed wastes in ranging of 18.50%, 17.51%, 12.79%, 10.66% and 9.59% respectively.

3. Carbohydrate content

Mushroom constitutesusually approx 50-60% of carbohydrate in dry matter form (Kalac 2012). On the other hand, it isknown for a good source of carbohydrates. This are mainly glycogen,chitin, cellulose, α- glucans/β-glucans and other hemicelluloses like Xylans, mannansand galactans (Manzi, 2001 and Hossain, 2007). a specific β-glucan is also present and isolated from pleurotus species called pleuran showing antitumor activity.. It is also knownforgood carbohydrates source and dietary fibers (Krishnamoorthy and Sankaran, 2014). Victor and Olatomiwa (2013), they stated that constitutive of the fungus, the carbohydrate content was higher at dry weight basis in P. ostreatus, which has grown on cupuacuexocarp, acacia seeds and pineapple skin. This content is relatively lower in Pleurotus grown on cotton waste (48.35%), on Pycnanthusongoleubis (45.75%) and on Ceibapentandra and Cananium sp. (41.87% and 44.56%) respectively.

4. Amino acid Composition

Victor and Olatomiwa (2013) reported that amino acid composition of P. ostreatus cultivated on different woody substrates. The amino acids found in abundant in pleurotus species are arginine, glutamic acid, threonine, aspartic acid, leucine and alanine etc. (Mbassi et al. 2018).

5. Lipids

Pleurotusspecies contain low fat and few essential fatty acids. Oleic acid and linoleic acid are the monounsaturated fatty acid and polyunsaturated fatty acid in P. ostreatusrespectively at the higher concentrations (Hossain, 2007). The lipid content in dried fruiting bodies of mushroom ranges from 0.2 to 8mg per 100 gram of powdered mushroom (Hossain, 2007). The lipid profile in nutritional contributionis inadequatebecause oflow total lipid content of mushroom Kalac, 2012).

6. Vitamins

Pleurotus species are rich in vitamins, mainly vitamin B, C and D (Manzi, 2004). According to Mattiala (2001) vitamin of group B are abundant in mushroom, particularly riboflavin, thiamine, nicotinic acid, pyridoxine, folic acid, ergosterol, phytoquinone, tocopherols and pyridoxine, etc. It also contains B group of vitamin than other mushroom species.

Medicinal value of mushroom

In addition to their nutritional value, oyster mushrooms have been found to be medically active in several therapies because they are rich in bioactive compounds that contain a variety of secondary metabolites including phenol compounds, polypeptides, terpenes and steroids. Various biologically active compounds present in mushrooms shows antioxidants properties. A different stage of formation of mushroom fruiting body consists of a range of biologically active metabolites.

Mushroom shows variousmedicinal functions such as antioxidant, liver protective, antidiabetic, anticancer,antifibrotic, anti-inflammatory, antidiabetic, antioxidant, antiallergic, antimicrobial properties immunomodulating, cardiovascular protector, antiviral, anticholesterolemic, antibacterial, antifungal, detoxification,hepatoprotective effects, antitumor development and inflammatory processes etc. (Valverde, 2015; Boonsong et al., 2016).

Factors affecting nutrient concentrations in fruiting bodies

Various factors are there which affects the nutrient profile of mushroom depending upon the type of substrate, sources of nitrogen and carbon nitrogen ratio as follows:

a. Substrate composition

Substrate composition is an important factor and directly affect the chemical structure of cultivated mushroom (Oyetayo and Ariyo, 2013). Agro waste is generated abundantly and it becomes an interesting substrate for the cultivation of mushroom, also environmental problems related to management of can also be eradicated (Ahmed, 2013). Pleurotus species of mushroom can be grown on a range of agro wastes like wheat straw etc. (Hussain, 2002; Pant, 2006), pine needles, corn straw (Dias, 2003), cotton wastes,  (Rizki and Tamai, 2011), paddy straw, weed plants (Das and Mukherjee, 2007), cardboard (Mandeel, 2005) banana leaves etc.

b. Sources of nitrogen

Nitrogen is essential element of nucleic acid, and protein (Miles and Chang, 1997). Nitrate is a nitrogen source for mushrooms (Martinez, 2011), it is accumulated in substrate composes an active enzyme system building hydroxylamine reductase, nitrate reductase and nitrite reductase, which catalyze the metabolic reaction of NO₃ to NH₂OH and then to glutamate (Bobics, 2015; Machado, 2015).

Economic importance of oyster mushroom

Mushrooms are economically important as it is primarily usedasfood for human consumption.  It has most of the minerals and trace elements required for the human diet. The folic acid present in ituseful forcuration ofanaemia. Due to its low sodium: potassium content, low starch, fat it has low calorific value.So, can be used as proper diet for people with hyper-tension, obesity and diabetes. Whereas high fibre content and ash allow them for the treatment in hyperacidity and constipation. Pleurotin, a polycyclic compound aromatic in nature has been isolated from the species. On the other hand, the organic wastes called spent mushroom compost generated after the harvesting of mushroom can be re-cycled and used as manure in agricultural practices asthis are ric in nitrogen sources. It also used as animal feed, bio-gas production and the slurry are used as manure which is economically profitable for agriculture field.

Future prospects and Conclusion

Mushroom cultivation technology has tremendous scope. P. ostreatus a popularly known edible mushroom cultivated globally. Mushrooms having excellent medicinal properties, rich in protein, fibre, and amino acids. This is a 100 % vegetarian food and is good for diabetes and joint pains. Pickles, pappad, soup powder, health powder, capsule and health drinks etc. can be made using mushroom. It has no cholesterol and helps in purifying blood. It has low sodium and substantial vitamin and minerals. It can be concluded that P. ostreatus cultivated on the lignocellulosic substrates are rich in essential nutrient such as high protein, carbohydrate, crude fiber, minerals and low in fats. Pleurotus mushroom holds promising potential in complementing the nutrient and minerals supply deficiencies prevention in a developing country. It consist of various biologically active components allowing for several therapeutic functions. Potential medicinal value is also high including boosting the immune system, controlling blood lipids, antitumor function and so on. In order to preserve the nutrients further, more complete and effective storage methods and culinary treatments are necessary. As pleurotus species are known for its exotic flavour and medicinal importance, furthermore researches should have been conducted to explore the benefits of mushroom and to seek the undiscovered species, which can provide abundant resources for the research of edible mushrooms.

References:

Ahmed M, Abdullah N, Ahmed KU, Bhuyan, MHMB (2013) Yield and nutritional composition of oyster mushroom strains newly introduced in Bangladesh.  Pesquisa Agropecuaria Brasileira, 2, 197-202.

 Alkoaik F, Khalil A, Fulleros R,  G. Reyes, R. (2015). Cultivation of Oyster Mushroom (Pleurotus Florida) on Date Palm Residues In an Environmentally Controlled Conditions in Saudi Arabia.  Advances in Environmental Biology, 9(3): 955-962.

 Bellettini MB, Fiorda FA ,Maieves HA,  Teixeira GL, Avila PS, Hornung AM, Ribani RH (2016) Factors affecting mushroom Pleurotus spp., Saudi Journal of Biological Sciences, doi: http://dx.doi.org/10.1016/j.sjbs.2016.12.005

 Boonsong  S, Klaypradit W, Pongtep W (2016) Antioxidant activities of extracts from five edible mushrooms using different extractants Agriculture and Natural Resources, 50, 89-97.

 Chang ST, Miles PG (2004) Mushrooms: Cultivation, Nutritional Value Medicinal Effect and Envirommental Impact, first ed. CRC Press, Boca Raton.

 Curvetto NR, Figlas D, Devalis R, Delmastro S (2002) Growth and productivity of different Pleurotus ostreatus strains on sunflower seed hulls supplemented with N-NH4 + and/or Mn (II). Bioresource and Technology. 84, 171-176.

 Das N Mukherjee M (2007) Cultivation of Pleurotus ostreatus on weed plants. Bioresource and Technology, 98, 2723-2726.

 Deepalakshmi K Mirunalini S (2014) Pleurotus ostreatus: an oyster mushroom with nutritional and medicinal properties. Journal of Biochemical Technology, 5(2): 718-726.

 Dias ES, Koshikumo EMS, Schwan RF, Silva R, (2003) Cultivation of the mushroom Pleurotus sajor-caju in different agricultural residues. Cien. Agrotec. 27, 1363-1369.

 Fanadzo, M, Zireva DT, Dube E, Mashingaidze AB (2010) Evaluation of various substrates and supplements for biological efficiency of Pleurotus sajor-caju and Pleurotus ostreatus. African Journal of Biotechnology 9, 2756–2761

 Hussain M, Khan SM, Khan SM, Chohan MA (2002) Effect of different sterilization methods on the production of oyster mushroom (Pleurotus ostreatus) on different substrates. In: Integrated plant disease management. Proceeding of 3rd National Conference of Plant Pathology, NARC, Islamabad: 1-3 Oct. 2001, pp. 159- 160.

 Hossain MS, Alam N, Amin SMR., Basunia MA Rahman A (2007). Essential fatty acids content of Pleurotus ostreatus, Ganoderma lucidum and Agaricus bisporus. Bangladesh Journal of Mushroom, 1:1-7.

 Jawad A, Ali MA, Ahmad W, Ayyub CM Shafi J (2013) Effect of different substrate supplements on oyster mushroom (Pleurotus sp.) production. Food science and technology 1(3): 44-51. DOI: 10.13189/fst.2013.010302.

 Jayakumar T, Thomas PA Sheu JR (2011) In-vitro and in-vivo antioxidant effects of the oyster mushroom Pleurotus ostreatus, Food Research International. 44:  851-861.

 Jongman M, Khare KB Loeto D (2018). Oyster mushroom cultivation at different production systems. European journal of biomedical and pharmaceutical sciences.  5(5): 72-79.

 Kinge TR, Adi EM, Mih AM, Ache NA, Nji TM (2016) Effect of substrate on the growth, nutritional and bioactive components of Pleurotus ostreatus and pleurotus florida. African Journal of Biotechnology. 15(27): 1476-1486.

 Krishnamoorthy D,  Sankaran M (2014) Pleurotus ostreatus: an oyster mushroom with nutritional and medicinal properties. Journal of Biochemistry and Technology, 5(2): 718-726.

  Liu SR Zhang WR & Kuang YB (2018) Production of stalk spawn of an edible mushroom (Pleurotus ostreatus) in liquid culture as a suitable substitute for stick spawn in mushroom cultivation, Scientia Horticulturae, 240 : 572-577.

 Ma L, Yan Q, Yang C, Zheng HY, Xiao LJ (2016) Production of liquid spawn of an edible mushroom, Sparassis latifolia by submerged fermentation and mycelial growth on pine wood sawdust. 209: 22-30.

 Machado ARG, Teixeira MFS, Kirsch LS, Campelo MCL, Oliveira, IMA (2015) Nutritional value and proteases of Lentinus citrinus produced by solid state fermentation of a lignocellulosic waste from tropical region. Saudi Journal of Biological Sciences and Horticulture. 193, 121-126.

 Mahalakshmi A, Suresh M, Rajendran S (2019) Cultivation of oyster mushroom (Pleurotus Florida) in various seasons on paddy straw Journal of Life Science Bioinformatics Pharmaceutical and Chemical Sciences DOI: 10.26479/2019.0506.07.

 Mallikarjuna SE, Ranjini A, Haware, DJ, Vijayalakshmi MR, Shashirekha MN  Rajarathnam  S (2013)  Mineral Composition of Four Edible Mushrooms pages http://dx.doi.org/10.1155/2013/805284

 Mandeel QA, Al-Laith, AA, Mohamad SA, (2005) Cultivation of oyster mushrooms (Pleurotus spp) on various lignocellulosic wastes. World Journal of Microbiology And Biotechnology. 21, 601-607.

 Mbassi Josian EG, Mobou Estelle Y, Ngome Francis A, Sado Kamdem SL (2018). Effect of substrates on nutritional composition and functional properties of Pleurotus ostreatus. 5(1): 15-22.

 Manzi P, Aguzzi A, Pizzoferrator L (2001)  Nutritional values of mushrooms widely consumed in Itlay. Food chemistry, 73(3): 321-325.

 Narayanasamy P, Suganthavel P, Sabari P, Divya D, Vanchinathan J, Kumar M (2008) Cultivation of Mushroom (Pleurotus Florida) By Using Two Different Agricultural Wastes in Laboratory Condition.

 Victor, O .O. and Olatomiwa, O. A. (2013). Micro and macronutrient properties of pleurotus ostreatus (Jacq: Fries) cultivated on different wood substrates. Jordan Journal of Biological Sciences, 6:223-226.

 Owaid, M.N., Abed, A.M., & Nassar, B.M., (2015). Recycling cardboard wastes to produce blue oyster mushroom Pleurotus ostreatus in Iraq. Emir. Journal of Food and Agriculture. 27, 537-541.

 Oyetayo VO, Ariyo OO, (2013) Micro and macronutrient properties of Pleurotus ostreatus (Jacq:Fries) Cultivated on Different Wood Substrates. Jordan Journal of Biological Sciences. 6, 223-226.

 Pant D, Reddy UG, Adholeya A, (2006). Cultivation of oyster mushroom on wheat straw and bagasse substrate amended with distillery effluent. World Journal of Microbiology and Biotechnology, 22, 267-275.

 Patil SS, Ahmed SA, Telang SM Baig MMV (2010) The nutritional value of Pleurotus ostreatus kumm cultivated on different lignocellulosic agrowastes, Innovative Romanian Food Biotechnology. http://www.bioaliment.ugal.ro/ejournl.htm.

 Piste P, Didwagh S and Mokashi A (2013). Calcium and its role in human body. International Journal of Research in Pharmaceutical and Biomedical Sciences, 4(2).