Agricultural wastes disposal is of primary concern in today’sworld as they are rich in nutrient and their disposal withoutpretreatment can cause leaching in field, which can causeenvironment pollution. To overcome this problem,mushroom cultivation on these agricultural wastes is themost ecofriendly method to reduce the level of nutrients atacceptable range to be used as manure. Besides overcomingthis problem defined combination of agricultural wastesalso gives high yield of mushroom in a cost effectivemanner.
Keywords
Mushroom; Agricultural wastes;Lignocellulosic; Protein; Cultivation
Introduction
Agricultural wastes are rich in various types of nutrients andtheir disposal is difficult to manage as excess of nutrients inthem can cause leaching is left in field, as a compost. Mostlythey are disposed by means of incineration which causespollution [1]. Hence, there is always a high demand ofdiscovering an agricultural waste management method which iscost effective and contribute less in environment pollution.Mushroom cultivation on agricultural wastes fulfills theserequirements [2].
Agricultural wastes are rich in lignincellulosic componentswhich are difficult to breakdown, but can effectively be donemushroom cultivation. Mushrooms are fleshly fungi, sporebearingfruiting bodies which are produced above ground onsoil. They often refer to fruiting body of the gill fungi, which donot contain chlorophyll like green plants and as a result cannotmanufacture food by their own. They are very nutritiousproducts that can be generated from lignocellulosic wastematerials. The bioconversion of agricultural wastes into a valueadded products is a good mean of their use [3-6]. The propertyof edible mushroom fungi to convert complex organiccompounds into simpler one’s is used to transform the uselessagricultural waste into valuable product [7]. Various edible mushroom strains are cultivated worldwide. Some of them aregiven below:
• Button -Agaricus
• Oyster -Pleurotous
• Shiitake -Lentinula Edodes
• Straw -Volvallella volvacea
• Chinese mushroom - Ganoderma
Besides having many nutrional values they are also useful inwaste management. The choice of species to cultivate dependson the availability of growth media. Oyster mushroom is thethird most cultivated edible mushroom in the world [8].Oystermushrooms are easiest to grow as they can grow on manysubstrates but their cultivation has one drawback as somepeople are allergic to their spores. In these cases, air-cleaningequipment or respirators are necessary in order to safely work inthe production facility. Because of the short shelf life this speciesoffer a special advantage to the local grower who marketsdirectly and can continuously deliver a fresh, high-qualityproduct.
Two mycorrhizal mushrooms, morels and truffles arecommercially cultivated. Mushroom cultivation offers benefitsto market gardens when it is integrated into the existingproduction system. Mushrooms are rich in various nutrients such as:
• Protein- Protein content of dry weight is between 18% and37%.
• Fat- Fat is present at low rate, content between 1-8%. Thehigh content of linollic acids is one of the reasons whymushrooms are considered healthy food.
• Vitamins and minerals - Mushrooms are a good source ofvitamins such as thiamine (Vitamin B), Riboflavin (vitaminB2) and ascorbic acid (vitamin C), folic acid. They also containsignificant amounts of phosphorus, sodium, potassium,calcium, magnesium, iron and Zinc [9,10].
Protein content of mushroom in paddy was significantlyhigher than in wheat straw while lipid content of mushroomswas higher in wheat straw than paddy straw [11]. Mushroomshave medicinal values as they contain substances which lowerthe cholesterol level in serum and liver which in turn makes it good for those suffering from heart diseases. Some of themcontain substances, which suppress the growth rate of tumors.
Free radicals can damage body cells and induce cancers. Freeradicals are the result of specific transformation process. Manybio active compounds protect the body against these radicals.These substances are often called anti oxidants and are presentin many mushrooms. In other words, the body immunity isboosted. This will be a relief to those suffering from HIV/AIDS.
History of Using Agricultural Wastes as aSubstrate
Agaricus bisporus, was first observed growing in melon cropcompost. Firstly, this mushroom was cultivated in open fieldsand later on moved underground into caves because of thepresence of appropriate weather conditions over there.
By 1865, the mushroom cultivation started in United States. InEurope, the first cultivated fungi, the mushroom, wasintroduced in the 17th century and in Netherland its cultivationbegan in 19th century. Japan and China were the countries whofirstly exploited its medicinal use. 80 years ago, sh*ttakemushroom (Lentinula edodes) was used to grow in China formedicinal purposes as it increases the immune response whengiven in addition to AIDS drugs.
Agricultural Wastes
Agricultural wastes are the good source for the cultivation ofmushrooms. Some of them are most commonly used such aswheat straw, paddy straw, rice straw, rice bran, molasses, coffeestraw, banana leaves, tea leaves, cotton straw, saw dust etc.
For the cultivation of Pleurotus rice straw, wheat straw andcotton straw are the substrates that are commonly used whilefor Agaricus, it is wheat straw which is usually used. Adisadvantage of straw is that it should be prepared first,especially if mushrooms are to be grown indoors. Straw is ladenwith other microbes, and it is necessary to get rid of those tinycompetitors, as there will be no scope of mushroom myceliumto grow in there presence.
Rice bran, coffee pulps are the main substrates used for thecultivation of Lentinula edodes. Banana leaves and tea leavesare used for Volvallella and Pleurotus respectively Sturion (1994)proposed using banana leaves for the cultivation of Pleurotusspp.
Ganoderma can be cultivated using sawdust [12]. Sawdustit*elf is often not nutritious enough and needs to besupplemented with a nitrogen source such as bran, urea,sunflower seed and horse manure.
Cultivation of oyster mushroom is of most concern as itsspores are allergic to some people, so related preventivemeasures should be done in working facility. Besides this, oystermushrooms have a short life span, so they are beneficial tothose growers who can sell them fresh in market (Tables 1-3).
| S. No | Agricultural waste | Strains |
|---|---|---|
| 1. | Rice straw Wheat straw Cotton straw Tea leaves Banana leaves | Pleurotus sp. |
| 2. | Wheat straw | Agaricus bisporus |
| 3. | Rice bran Coffee pulp | Lentinula edodes |
| 4. | Tea leaves | Volvallella |
| 5. | Sawdust | Ganoderma |
Table 1: Various types of agricultural wastes used for mushroomcultivation.
| S. No | Substrate | Composition |
|---|---|---|
| 1. | Wheat straw | 1% protein 13% lignin 39% hemicelluloses 40% cellulose |
| 2. | Rice straw | 41% cellulose 14% lignin 0.8% total nitrogen 0.25% P2O5 0.3% K2O 6% SiO2 pH 6.9 |
| 3. | Sugarcane bagasse | Cellulose 35-40% Hemicellulose 20-25% Lignin 18-24% Ash 1-4% Waxes <1% Nitrogen 0.7% |
Table 2: Composition of various types of substrate [14].
| S. No | Substrate (in combination) | Strain | Effect |
|---|---|---|---|
| 1. | Barley straw+wheat bran and wood chips+soybean powder+rice bran treatments | Pleurotus eryngii | 4.64% protein content |
| 2. | Wheat straw+wheat bran+soybean powder treatment | Pleurotus eryngii | 13.66% protein content |
| 3. | soybean straw+wheat straw | Pleurotus sajorcaju | 87.3% Biological efficiency |
| 4. | soybean straw+saw dust | Pleurotus sajorcaju | 43.8% Biological efficiency |
| 5. | corncob (CC)+sugarcane bagasse | Pleurotus ostreatus Pleurotus cystidiosus | High content of protein, ash and mineral (Ca, K, Mg, Mn, and Zn) |
Table 3: Combination of substrates reported on various strains and their effect.
Correlation of Agricultural WastesComposition With Mushroom Cultivation
For high yield of mushroom cultivation, it is necessary that theentire nutritional requirement should be fulfilled in optimumconcentration as various researches has reported low yieldwhen nutrients in a medium are either in low or highconcentration. Banana stalk and Bahia grass are used for thecultivation of Pleurotus sajor-caju with biological efficiency of74.4% and 74.12% respectively but there is a low yield whenthey are supplemented with other components. This can be dueto high nitrogen concentration which hinders its yield [13].
Growth of Pleurotus ostreaus resulted similar in paddy strawand wheat straw while in sugarcane bagasse it resulted in lowyield. Reason behind this selective high yield must beappropriate concentration of lignin, hemicelluloses, cellulose insubstrate [14].
There is a Positive correlation of cellulose: lignin with myceliagrowth and high yield in Pleurotus ostreatus and carbon: nitrogen ratio with mushroom yield in Pleurotus eryngii andAgaricus aegerita while in V. volvacea strains high yield is relatedto cellulose content [15].
Combination Of Agricultural SubstratesUsed For Cultivation
In addition to the use of supplements with agricultural wastesas a substrate, various combination of agricultural wastes arealso used for the cultivation and are reported to be optimalsubstrate.
Vegetable waste when used in combination with paddy strawresulted in high yield of oyster mushroom [16]. To cultivate P.ostreatus sawdust in addition to rice husks is reported as anoptimal substrate [17]. The quality of P. eryngii was significantlyaffected by substrate ingredients. On barley straw and sugarbeet pulp substrate complemented with rice bran, highestmushroom fresh weight and moisture content were achieved[18].
For Pleurotus sajor-caju, combination of soybean straw, wheatstraw showed significantly highest yield while soybean straw andsaw dust combination showed significantly lesser yield [19].
Supplements Used With AgriculturalWastes
Agricultural wastes are used in addition to varioussupplements such as gypsum, lime and urea. Gypsumcontributes as a calcium source and regulates the acidity level.Water holding capacity of gypsum is high which prevent excesswetting of the substrate. Lime is used to adjust pH. Mushroomcultivation needs appropriate nitrogen content for high yield,which can be fulfill by various components such as urea, bran,sunflower seed, molasses, horse manure [20].
Optimum Conditions For Cultivation
• Besides having appropriate composition for significantly highyield of mushroom, optimum conditions of the environmentduring cultivation should also be maintained. Given beloware the usual optimum conditions that should be maintainedduring cultivation.
• Temperatures of 15-35°C
• pH of about 6.5
• Carbon dioxide (CO2) level to be between 15-20%
• Humidity to be between 86-90%
• CO2 should be between 0-0.6%.
• Temperatures and humidity levels should be regulated at86% and 10-28°C respectively.
Future Aspects and Advantages
India, being a second major producer of vegetables in theworld; contributes 14% of total world vegetable production.Taking estimated production of fruits and vegetables in India at 150 million tons, the total waste generation comes to about 50million tons per annum. Due to their chemical composition fruitsand vegetables wastes are more prone to spoilage than cereals,which create unhygienic condition leading to spread of diseasesand loss of resources. The vegetable wastes are a rich innitrogen and carbohydrate but are not fit for consumption.These wastes can be utilized for the production of various typesof mushroom such as the oyster variety.
In the recent times the waste management is of mostconcern. Proper management and execution of waste disposalpractices have become today’s need. The inappropriatemanagement of waste gives rise to many problems such as rapidspread of infectious diseases, development of new varieties ofdiseases. The exponential increase in the present amount ofwaste produced brings to notice an immediate requirement ofsolution to overcome this problem.
An agricultural waste consists of lignin and cellulose, whichare difficult to breakdown. They are insoluble and bind to inertsubstances in soil and get out of reach of bacterial culture present in soil. While mushroom’s mycelium releasesextracellular enzymes, which are responsible for the lignindegradation. Pleurotus and Lentinus have their own enzymessystems based on endoglucanase, laccase and phenoloxidases.The large amount of agricultural wastes and appropriate climaticconditions provide massive scope for oyster mushroomcultivation in Sagar, M.P. [21].
An agricultural waste provides the opportunity for costeffective farming. Even after being used for mushroomcultivation, it can be used later on as manure for agriculturalfield as now the nutrient contents are at acceptable range.Cultivation of mushroom on these residual wastes is one of the most eco-friendly practices to fight the malnutrition andenvironmental pollution caused by these wastes. Variousresearches is still going on to exploit the potential of agriculturalwastes either by using them in combination or by giving them pretreatment.
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