**1. Introduction**

Mushrooms have been recognized as the alternate source of good quality protein. They are capable of producing the highest quantity of protein per unit area and time from agro-wastes which are available to the tune of more than 300 million tons per annum in India. Many species of mushrooms are cultivated world-wide. Seventy percent of the global mushroom production is derived from three mushroom groups, *Agaricus bisporus, Pleurotus* spp., and *Lentinula edodes*. The remaining mushroom volume is generated by at least a dozen species [1].

Edible mushrooms commonly have insignificant lipid level with higher proportion of polyunsaturated fatty acids. All these result in low calorific yield from mushroom foods. Mushrooms do not have cholesterol. Instead, they have ergosterol that acts as a precursor for Vitamin D synthesis in human body. Similarly, ergosterol in button mushroom is converted in to vitamin D2 when exposed to UV radiation

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 amino acids (Methionine and cysteine) [2].

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 immunomodulation activities [12].

#### **1.1 Spent mushroom substrate**

After the cultivated mushroom have exhausted the nutrients within the substrates, and there were no more fruitbodies harvest, the so called remains, regarded as "the useless material" is known as spent mushroom substrate (SMS) [13].

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 considering environmental repercussion.

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 diversified than what is normally predicted.

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

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

**249**

*Screening and Potential Uses of Contaminated Spent Mushroom (*Pleurotus *spp.)*

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

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.

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

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

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

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

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

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.

role of this extract in improving plant defense and growth [29, 30].

content in the spent substrate in relation to the initial one.

*DOI: http://dx.doi.org/10.5772/intechopen.93863*

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

**2.3 Spent mushroom substrate (SMS)**

**2. Review of literature**

mankind [24].

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

*Escherichia coli* [27, 28].

**2.4 Composition of SMS**

*Screening and Potential Uses of Contaminated Spent Mushroom (*Pleurotus *spp.) DOI: http://dx.doi.org/10.5772/intechopen.93863*
