**2. Review of literature**

*Emerging Contaminants*

lation activities [12].

**1.1 Spent mushroom substrate**

ering environmental repercussion.

diversified than what is normally predicted.

surviving and multiplying in the soil ecosystem.

**1.2 The Management of Spent Mushroom Substrate (SMS)**

amino acids (Methionine and cysteine) [2].

or sunlight. The protein content of edible mushrooms is usually high, but varies greatly. The crude protein content of mushrooms varied from 12 to 35% dry weight depending upon the species. The free amino acids composition differs widely but in general they are rich in theronine and valine but deficient in sulfur containing

Antibiotic resistance has become a global concern [3]. The clinical efficacy of many existing antibiotics is being threatened by the emergence of multidrug resistant pathogens [4–6]. Already, a number of antibacterial compounds have been isolated from Basidiomycetes fungi, including Collybial and Frustulosin [7–9].

*Pleurotus* spp. are mushrooms which belong to the class basidiomycetes. They are generally understood to be called white rot fungi, because of their ability to degrade lignocellulosic materials. The oyster mushroom consists of a number of several edible *Pleurotus* species. This species represented 14% of the world production in 1997 [1]. *Pleurotus* mushrooms are edible with excellent flavor and taste. They have nutritional as well as medicinal properties [10]. They are low in calories, fats, sodium, carbohydrates and cholesterol, while being rich in proteins, minerals, vitamins and fibers [11]. *Pleurotus* spp.is promising as medicinal mushrooms, exhibiting hematological, antiviral, antitumor, antibiotic, antibacterial, hypocholesterolic and immunomodu-

After the cultivated mushroom have exhausted the nutrients within the substrates, and there were no more fruitbodies harvest, the so called remains, regarded

The disease suppressive properties of composting materials are known for many decades and much scientific evidence have revealed favorable properties of composts for the management of plant diseases [21, 22]. Due to the unique chemical constitution and the microflora present in SMS, its application can be more

Actinomycetes, bacteria and fungi inhabiting the compost, not only play role in its further decomposition but also exert antagonism to the normal pathogens

Several agro industrial wastes could be used to prepare mushroom composts. These growing substrates may be composed from different wastes materials such as sawdust, rice straw, bedded horse manure, cotton wastes, paper wastes, cocoa shells, wheat straw, maize husks and various other wastes [14]. Additives such as rice bran, calcium carbonate or wheat bran may be added to enhance mushroom fructification [15]. Compost is considered "spent substrate" when one full crop of mushroom has been taken and further extension becomes unremunerative [16–18]. Mushroom industry needs to dispose off more than 50 million tons of used mushroom compost each year called Spent Mushroom Substrate (SMS) [19]. Recently, the term spent compost or spent mushroom substrate has been replaced by a more appropriate term, "post mushroom substrate" because it is not "spent" and is ready to be further attacked by a new set of microorganisms. The large dumped piles of spent mushroom substrate become anaerobic and give off offensive odor. The run-off from such piles contaminates nearby water sources and pollutes them [20]. Under normal circumstances, the spent mushroom substrate is discarded as waste without consid-

as "the useless material" is known as spent mushroom substrate (SMS) [13].

**248**

Mushroom is a macrofungus with a distinctive fruiting body, which can be either hypogeous or epigeous, large enough to be seen with the naked eye and to be picked by hand [23]. The number of mushroom species on the earth is estimated to be 1,40,000 suggesting that only 10% are known. Assuming that the proportion of useful mushrooms among the undiscovered and unexamined mushrooms will be 5%, which implies 7000 yet undiscovered species will be of possible benefit to mankind [24].

#### **2.1** *Pleurotus* **spp.**

Mushrooms are considered as a functional food, which can provide health benefits beyond the traditional nutrients they contain [25, 26]. Nowadays, several species of Pleurotus are cultivated commercially because of their rich mineral contents and medicinal properties, short life cycle, reproducibility in the recycling of certain agricultural and industrial wastes and low demand on resources and technology.

#### **2.2 Anti-microbial activity of** *Pleurotus* **spp.**

Water and alcoholic extracts from *P. ostreatus* mycelium have been used in studies on antimicrobial activities against numerous types of microbes. The highest potency was shown by water extract, especially towards fungi, *Candida albicans, Cryptococcus humicola, Trichosporon cutaneum* and bacteria *Staphylococcus aureus* and *Escherichia coli* [27, 28].

The antimicrobial properties of mushroom extracts and highlighted some of the active compounds identified, including low- and high-molecular weight compounds which showed antagonistic activity against gram positive bacteria. LMW compounds are mainly secondary metabolites, such as sesquiterpenes and other terpenes, steroids, anthraquinones, benzoic acid derivatives, and quinolines, but also primary metabolites such as oxalic acid. HMW compounds are mainly peptides and proteins.

#### **2.3 Spent mushroom substrate (SMS)**

After mushroom cultivation, the partially degraded paddy or wheat straw and other agricultural waste, which form as valuable by-products of edible mushroom cultivation, have been termed as Spent Mushroom Substrate (SMS). Antibacterial activity of *H. erinaceus* SMS against phyto-pathogenic bacteria and evaluated the role of this extract in improving plant defense and growth [29, 30].

#### **2.4 Composition of SMS**

The macro and micronutrients of the raw material and the initial and spent substrates of *Pleurotus ostreatus* [31–33]. The mineral composition of the fruiting body varied with the substrates, which made possible the production of a fruiting body rich in K, P, Mg and Fe. Potassium was the mineral with the highest content in the fruiting body in all substrates tested. There was an increase in protein and mineral content in the spent substrate in relation to the initial one.

The pH of the compost was found to be 7.58 and the electrical conductivity of the compost was found to be 0.71 dms−1. Chemical analysis of the compost showed varying organic matter and nutrient content. The carbon to nitrogen (C: N) ratio of a product was 13:1 and the bioavailability of total potassium (2.64%), magnesium

(2.26%) and calcium (5.16%) were comparatively higher to the availability of total phosphorous (0.48%) and sodium (0.29%).
