**2.1 History**

Fossil finds have revealed that fungi exist since the Cretaceous period (approximately 130 million years ago), long before humanity (Chang, 1993). Fungi (mushrooms), also called macromycets, belong to the Fungi Kingdom, being known by man since the most remote period of human history. Edible mushrooms were first collected by man in China and dates from 5000-4000 BC. (Zhanxi and Zhanhua, 2001). It is estimated that the first cultivation of edible mushrooms in China started in the early 7th century, with the species *Auricularia auricula* (Chang and Miles, 1987). China is a country with a long tradition in cultivation and consumption of mushrooms and according to Zhanxi and Zhanhua (2001), it has more than ten species of fungi which are currently cultivated in several countries of the world. That country is a pioneer in the cultivation and consumption of edible and medicinal mushrooms, followed by Japan, Europe and The United States (Urben et al., 2001).

Edible mushrooms were described as the "food of the Gods" and as such, confirmed by Roman gourmets who appreciated them as a kind of spice. The Chinese considered them as the "elixir of life". The Greeks believed that the mushrooms were able to give strength to warriors in battles and the Egyptian pharaohs also nourished themselves on these spices (Chang and Miles, 1984). Mushrooms had a wide acceptance, and some species are considered as "Kings of the dining table" or "kitchen diamonds" (Zhanxi and Zhanhua, 2001).

The Greeks Euripides, Theophrastus and Plinio have described the consumption of edible mushrooms in their time (Guzmán et al*.,* 1993). In some societies, the mushroom was a royal food, probably by its pleasant flavor and texture (Miles and Chang, 1997).

The Romans knew several edible and poisonous fungi. There is a story about the Emperor Julius Caesar who was very fond of *Amanita caesarea* mushroom, whose scientific name was a homage to him and for that reason, it became known as "Mushroom of the Caesars" (Guzmán et al., 1993).

According to Molena (1986), the species *Polyporus tuberoster* (*fungaie stone*) and *Polyporus corilinus* are among the first cultivated mushrooms, collected from the wood of hazels and eucalyptus. These fungi were consumed in 4-5 cm slices, and their production demanded about six months, yielding sometimes one or two mushrooms at a time. There was neither any knowledge about their nutritional requirements, nor about their growth cycle. The only thing that was known was that rubbing a mature mushroom on those woods, and leaving them in a wet environment during a particular period of the year could produce appreciable mushrooms (Molena, 1986).

During the Roman Empire the fungaie stone (stone that produces the mushroom) appeared in Italy, which was composed of a cluster of humus, leaves, twigs and limestone rocks, forming a compact mass, which was cut in blocks in the form of bricks and transported to the royal palaces. They were kept in a damp place and irrigated daily until harvest time to serve the senators and other members of the Roman aristocracy (Molena, 1986). In France, the mushroom cultivation began during the reign of Luis XIV, according to Molena (1986). However, the cultivation of *Agaricus bisporus*, the "Champignon de Paris", the most widely cultivated and commercialized species, has been produced since about 1650 (Delmas, 1978; Chang and Miles, 1984).

With the advances of knowledge and technology of mushroom cultivation, commercial production of dozens of species became viable in several countries in recent decades (Guzmán et al., 1993; Stamets, 1993; 2000; Vedder, 1996; Eira, 2000), reaching a production of approximately 4.3 million tons of edible mushrooms in 1991 (Miles and Chang, 1997). The world current production is around 6.2 million tons (Chang, 2003).

Fossil finds have revealed that fungi exist since the Cretaceous period (approximately 130 million years ago), long before humanity (Chang, 1993). Fungi (mushrooms), also called macromycets, belong to the Fungi Kingdom, being known by man since the most remote period of human history. Edible mushrooms were first collected by man in China and dates from 5000-4000 BC. (Zhanxi and Zhanhua, 2001). It is estimated that the first cultivation of edible mushrooms in China started in the early 7th century, with the species *Auricularia auricula* (Chang and Miles, 1987). China is a country with a long tradition in cultivation and consumption of mushrooms and according to Zhanxi and Zhanhua (2001), it has more than ten species of fungi which are currently cultivated in several countries of the world. That country is a pioneer in the cultivation and consumption of edible and medicinal

mushrooms, followed by Japan, Europe and The United States (Urben et al., 2001).

food, probably by its pleasant flavor and texture (Miles and Chang, 1997).

Edible mushrooms were described as the "food of the Gods" and as such, confirmed by Roman gourmets who appreciated them as a kind of spice. The Chinese considered them as the "elixir of life". The Greeks believed that the mushrooms were able to give strength to warriors in battles and the Egyptian pharaohs also nourished themselves on these spices (Chang and Miles, 1984). Mushrooms had a wide acceptance, and some species are considered as "Kings of the dining table" or "kitchen diamonds" (Zhanxi and Zhanhua,

The Greeks Euripides, Theophrastus and Plinio have described the consumption of edible mushrooms in their time (Guzmán et al*.,* 1993). In some societies, the mushroom was a royal

The Romans knew several edible and poisonous fungi. There is a story about the Emperor Julius Caesar who was very fond of *Amanita caesarea* mushroom, whose scientific name was a homage to him and for that reason, it became known as "Mushroom of the Caesars"

According to Molena (1986), the species *Polyporus tuberoster* (*fungaie stone*) and *Polyporus corilinus* are among the first cultivated mushrooms, collected from the wood of hazels and eucalyptus. These fungi were consumed in 4-5 cm slices, and their production demanded about six months, yielding sometimes one or two mushrooms at a time. There was neither any knowledge about their nutritional requirements, nor about their growth cycle. The only thing that was known was that rubbing a mature mushroom on those woods, and leaving them in a wet environment during a particular period of the year could produce appreciable

During the Roman Empire the fungaie stone (stone that produces the mushroom) appeared in Italy, which was composed of a cluster of humus, leaves, twigs and limestone rocks, forming a compact mass, which was cut in blocks in the form of bricks and transported to the royal palaces. They were kept in a damp place and irrigated daily until harvest time to serve the senators and other members of the Roman aristocracy (Molena, 1986). In France, the mushroom cultivation began during the reign of Luis XIV, according to Molena (1986). However, the cultivation of *Agaricus bisporus*, the "Champignon de Paris", the most widely cultivated and commercialized species, has been produced since about 1650 (Delmas, 1978;

With the advances of knowledge and technology of mushroom cultivation, commercial production of dozens of species became viable in several countries in recent decades (Guzmán et al., 1993; Stamets, 1993; 2000; Vedder, 1996; Eira, 2000), reaching a production of approximately 4.3 million tons of edible mushrooms in 1991 (Miles and Chang, 1997). The

world current production is around 6.2 million tons (Chang, 2003).

**2.1 History** 

2001).

(Guzmán et al., 1993).

mushrooms (Molena, 1986).

Chang and Miles, 1984).

**2.2 An overview of the commercial cultivation of edible fungi in the world and in Brazil**  After World War II, the edible mushroom industry grew from 350,000 tons in 1965 to 4.3 million tons in 1991, from which 3.4 million tons belong to the six most worldwide important genera: *Agaricus, Pleurotus, Lentinula, Auricularia, Volvariella* and *Flammulina*. The major producers are China, Japan, USA and France (Miles and Chang, 1997). The most cultivated genera are *Agaricus, Pleurotus* and *Lentinula*. This increase was due to several factors, among them: a) the increase in the number of species on a commercial scale; b) the

development of cultivation techniques using plastic bags, which allowed many wood decomposers edible fungi to be grown on lignocellulosic residues, preferably the cultivation on logs, reducing considerably the cultivation time; c) due to the marketing techniques highlighting the nutritional merits of mushrooms as an important part of the diet, so they wouldn't be marketed as simple accompaniments or delicacies, but as a food of high nutritional value (Miles and Chang, 1997).

The literature cites approximately 200,000 species of fungi existing in the world, from which, about 2,000 are potentially edible species. However, only 25 of them are commonly used as food, and fewer still are commercially cultivated (Chang and Miles, 1984; Chang, 1980; Bononi, 1999).

In the early 1980s, only *Agaricus bisporus* (Champignon de Paris) and other species of this genus and "shiitake" (*Lentinus edodes*, currently named *Lentinula edodes*) had a modern technology for commercial production, where 70% of the world production was represented by *Agaricus* and 14% by *Lentinula* (Chang and Miles, 1984). However, according to the same authors, the world's attention is turning to the development of new technologies for different species of worldwide known edible mushrooms, especially considering the difficulties of production in tropical and subtropical climates. Special technologies are being developed in several countries allowing the cultivation of: *Volvariella volvaceae* in China, Taiwan, Japan, Philippines and Indonesia; *Kuehneromyces mutabilis*, *Flamulina velutipes*, *Hypholoma capnoides* and *Coprinus comatus* in some countries of Europe and Asia; *Pleurotus ostreatus* in Italy, Hungary, West Germany, Mexico and Brazil (Chang and Miles, 1984; Guzman et al., 1993; Eira and Minhoni, 1997; Bononi et al., 1999; Zhanxi and Zhanhua, 2001; Urben et al., 2001). This way, the overview of the world production has changed suddenly, showing a considerable increase in cultivation and consumption of *Pleurotus* as reported by Eira (1997) adaptated by Fermor (1993).

An adaptation based on Fermor (1993), made by Eira et al. (1997), the world production of cultivated mushrooms in the early 1990s was 1,424,000 tons for *Agaricus bisporus*, 900,000 tons for *Pleurotus* spp, 393,000 tons for *L. edodes* and 887,000 tons for other mushrooms, representing, respectively, 39.51%, 24.98%, 10.91% and 24.61%. The current trend is to increase production.

Concerning the production of mushrooms in Brazil, there is not a precise documentation that could allow us to determine when the cultivation of mushrooms started in the country (Fidalgo and Guimarães, 1985). Its popularization in the Center-South region of Brazil dates back to 50 years ago. Bononi (1999) reports that the cultivation of champignon (*Agaricus*) began in 1953, when the Chinese immigrants settled in Mogi das Cruzes and the Italian Oscar Molena in Atibaia, brought technology and imported strains of their countries. For Molena (1985), mushroom cultivation began in 1953 and developed after the poultry crisis in the period of 1955-1959, when breeders began to use chicken sheds for the cultivation of mushrooms, without proper technical conditions.

The commercial cultivation of edible fungi in Brazil is limited to *Agaricus bisporus*  (champignon), *Lentinula edodes* (shiitake) and *Pleurotus* spp, known as oyster mushroom,

Productivity and Nutritional Composition of *Lentinus strigosus* (Schwinitz)

*Agaricus bisporus* 8,000 ton *Pleurotus ostreatus* 2,000 ton *Lentinula edodes* 1,500 ton *Agaricus blazei* 500 ton *Other species* 50 ton

Table 1. Annual production of mushrooms in Brazil. Source (Souza, 2011).

**2.3 The importance of fungi** 

(Chang, 1993).

bioconversion of lignocellulosic residues.

microorganisms (Matheus and Okino, 1999).

residue of the residue (Chang, 2003).

Fries Mushroom from the Amazon Region Cultivated in Sawdust Supplemented with Soy Bran 231

The importance of fungi is unlimited in the terrestrial ecosystem and consequently in man's life. However, these organisms can be beneficial or not, according to the results of their actions. If we consider the decomposing action of fungi on food and the associated production of toxic substances (mycotoxins), the decomposition of other materials such as wood, pathogenicity caused to plants, animals and man, this is the negative aspect of it. On the other hand, if we consider the important role in the decomposition, which along with other microorganisms, participate in the mineralization of organic matter, as well as the symbiosis with plants in the process of mycorrhizae formation, bioremediation, biological control, food, and medicinal properties, one can see the positive side of these organisms. In nature, the fungi do not participate only in the role of providing a food source for humans and other animals; they also play an important role in the cycling of carbon and other elements, by breaking the lignocellulosic residues and animal excrements which serve as a substrate for saprophytic fungi. This way, these decomposing agents play a very important environmental role along with other organisms, complementing the cycling of plants and animals. Simultaneously, they produce multiple enzymes that degrade complex substances that allow the absorption of soluble substances used for their own nutrition

Trufem (1999) and Matheus and Okino (1999) highlight the importance of fungi in the context of biotechnology, where they are widely used in the food industry, pharmaceutical industry, bioremediation, in biosorption (removal of heavy and radioactive metals), in agriculture as arbuscular mycorrhizal fungi (AMF), where they are used in techniques that help the development of plants of economic interest, biological control, xenobiotics biodegradation, bioremediation of the soil, treatment of industrial effluents and

One of the most important processes from an economic point of view is the use of fungi in the conversion of lignocellulosic residues in edible mushrooms by fungus X substrate interaction, enabling the solid fermentation process, through enzymatic system of these

The cultivation of edible mushrooms has become an increasingly important practice in modern society due to the biotechnological process of bioconversion of various residues in edible mushrooms or in dietary supplements of high nutritional value, enabling a more efficient utilization of materials, besides, it can reduce the volume of waste or accelerate the decomposition process. This way, the residual substrate obtained from the cultivation of edible mushrooms can also be used as soil conditioner, natural fertilizer, or food for animals, closing the exploitation cycle of raw materials (Miles and Chang, 1997), which today is called "zeri" technology, trying to get the maximum use of such material, eliminating the

giant mushroom or caetetuba (Bononi et al., 1999; Eira, 2000). Varieties or strains of mushrooms of the *Pleurotus* genus gave origin to the "hiratake" (mushrooms with very large basidiocarp, harvested in mature stage with opened basidiocarps, before they turn their edges upwards and with more than 5 cm in diameter) and the "shimeje" (with long stipes, harvested with their basidiocarps very young and dark, smaller than 5 cm, and can be harvested in bunches) (Eira and Minhoni, 1997).

There are few Brazilian research reports about the subject, and the Botanical Institute of São Paulo was one of the pioneers, creating a research center of edible mushrooms in Mogi das Cruzes in 1985 and a teaching, research and extension nucleus was created in the Faculty of Agronomic Sciences/UNESP in Botucatu, in 1986, named Module of Mushrooms (Eira, 2000). Other centers are springing up in many universities and research institutions.

The production of edible mushrooms in Brazil is difficult to be evaluated. Producers give preference (90%) to the cultivation of *A. bisporus*, (Bononi et al., 1999). Among producers, the majority, almost 90%, are from the East of Taiwan, China, Korea, Japan, working in small properties, in a family system, with all family members operating in all stages of cultivation, in a collective way. The region of the city of Mogi das Cruzes, São Paulo, is responsible for approximately 70% of the edible mushrooms commercialized in Brazil. The remainder are produced by other municipalities, most of them also in São Paulo, Ribeirão Pires, Suzano, Cabreúva, Atibaia, Mariporã, Sorocaba (Bononi et al., 1999; Souza, 2011). There are some important producers in Porto Alegre and some producing installations in southern Minas Gerais and Paraná States.

In 1990, the production of Mushrooms was only 3,000 tons according to Eira et al. (1997), being estimated at 10,000 tons per year until 1997. According to the APAN (Natural Agriculture Producers Association), the Brazilian production of shiitake in late 1995 among its associates, was approximately six tons per month. The official data are underestimated, because they include only the mushrooms marketed by CEAGESP (General Supply Center of São Paulo State) and those intended for export, which are recorded by the CACEX-Department of Foreign Trade (Eira et al., 1997; 2004; Bononi et al., 1999). It is known, however, that significant amounts are marketed directly by the producers with restaurants, pizzerias, snack bars and other establishments, as well as street markets.

Brazilian productivity of *Agaricus bisporus* "Champignon de Paris" in Mogi das Cruzes (in São Paulo State) until 2000 was of the order of 5 to 7 kg of fresh mushrooms/100 kg of moist substrate (4 to 6 kg of fresh mushroom/m2) (Eira, 2000). In Europe, however, in countries such as Belgium, Holland, Germany and France, the average productivity of mushroom at that time was 30 kg/100 kg of substrate.

Currently in Brazil, farms with more technology get on average a productivity (substrate conversion in mushrooms) for "Champignon de Paris" ranging from 18 to 24% in 20 to 30 days of the crop cycle. In more rustic crops this conversion varies from 12 to 15% in 70 to 90 days. While the numbers seem to have greatly increased, yet it is little when compared to Asian and European productions, where they manage 30 to 40% of conversion (Souza, 2011). Even today there are no official data concerning the production of mushrooms in Brazil, but some unofficial sources report that 12,050 tons a year of mushrooms "in natura" (table 1). Since 1995, there is an annual import of 12,000 tons per year, on average, most of it cooked *Agaricus bisporus*, to meet market demand. Therefore, it can be concluded that, Brazilian consumption is much higher than its production, reaching 24,050 tons per year. In this context Brazilian people consume around 130 g per capita (Souza, 2011). The world production is around 6.2 million tons (Chang, 2003).


Table 1. Annual production of mushrooms in Brazil. Source (Souza, 2011).

#### **2.3 The importance of fungi**

230 Recent Trends for Enhancing the Diversity and Quality of Soybean Products

giant mushroom or caetetuba (Bononi et al., 1999; Eira, 2000). Varieties or strains of mushrooms of the *Pleurotus* genus gave origin to the "hiratake" (mushrooms with very large basidiocarp, harvested in mature stage with opened basidiocarps, before they turn their edges upwards and with more than 5 cm in diameter) and the "shimeje" (with long stipes, harvested with their basidiocarps very young and dark, smaller than 5 cm, and can be

There are few Brazilian research reports about the subject, and the Botanical Institute of São Paulo was one of the pioneers, creating a research center of edible mushrooms in Mogi das Cruzes in 1985 and a teaching, research and extension nucleus was created in the Faculty of Agronomic Sciences/UNESP in Botucatu, in 1986, named Module of Mushrooms (Eira,

The production of edible mushrooms in Brazil is difficult to be evaluated. Producers give preference (90%) to the cultivation of *A. bisporus*, (Bononi et al., 1999). Among producers, the majority, almost 90%, are from the East of Taiwan, China, Korea, Japan, working in small properties, in a family system, with all family members operating in all stages of cultivation, in a collective way. The region of the city of Mogi das Cruzes, São Paulo, is responsible for approximately 70% of the edible mushrooms commercialized in Brazil. The remainder are produced by other municipalities, most of them also in São Paulo, Ribeirão Pires, Suzano, Cabreúva, Atibaia, Mariporã, Sorocaba (Bononi et al., 1999; Souza, 2011). There are some important producers in Porto Alegre and some producing installations in southern Minas

In 1990, the production of Mushrooms was only 3,000 tons according to Eira et al. (1997), being estimated at 10,000 tons per year until 1997. According to the APAN (Natural Agriculture Producers Association), the Brazilian production of shiitake in late 1995 among its associates, was approximately six tons per month. The official data are underestimated, because they include only the mushrooms marketed by CEAGESP (General Supply Center of São Paulo State) and those intended for export, which are recorded by the CACEX-Department of Foreign Trade (Eira et al., 1997; 2004; Bononi et al., 1999). It is known, however, that significant amounts are marketed directly by the producers with restaurants,

Brazilian productivity of *Agaricus bisporus* "Champignon de Paris" in Mogi das Cruzes (in São Paulo State) until 2000 was of the order of 5 to 7 kg of fresh mushrooms/100 kg of moist substrate (4 to 6 kg of fresh mushroom/m2) (Eira, 2000). In Europe, however, in countries such as Belgium, Holland, Germany and France, the average productivity of mushroom at

Currently in Brazil, farms with more technology get on average a productivity (substrate conversion in mushrooms) for "Champignon de Paris" ranging from 18 to 24% in 20 to 30 days of the crop cycle. In more rustic crops this conversion varies from 12 to 15% in 70 to 90 days. While the numbers seem to have greatly increased, yet it is little when compared to Asian and European productions, where they manage 30 to 40% of conversion (Souza, 2011). Even today there are no official data concerning the production of mushrooms in Brazil, but some unofficial sources report that 12,050 tons a year of mushrooms "in natura" (table 1). Since 1995, there is an annual import of 12,000 tons per year, on average, most of it cooked *Agaricus bisporus*, to meet market demand. Therefore, it can be concluded that, Brazilian consumption is much higher than its production, reaching 24,050 tons per year. In this context Brazilian people consume around 130 g per capita (Souza, 2011). The world

pizzerias, snack bars and other establishments, as well as street markets.

2000). Other centers are springing up in many universities and research institutions.

harvested in bunches) (Eira and Minhoni, 1997).

Gerais and Paraná States.

that time was 30 kg/100 kg of substrate.

production is around 6.2 million tons (Chang, 2003).

The importance of fungi is unlimited in the terrestrial ecosystem and consequently in man's life. However, these organisms can be beneficial or not, according to the results of their actions. If we consider the decomposing action of fungi on food and the associated production of toxic substances (mycotoxins), the decomposition of other materials such as wood, pathogenicity caused to plants, animals and man, this is the negative aspect of it. On the other hand, if we consider the important role in the decomposition, which along with other microorganisms, participate in the mineralization of organic matter, as well as the symbiosis with plants in the process of mycorrhizae formation, bioremediation, biological control, food, and medicinal properties, one can see the positive side of these organisms.

In nature, the fungi do not participate only in the role of providing a food source for humans and other animals; they also play an important role in the cycling of carbon and other elements, by breaking the lignocellulosic residues and animal excrements which serve as a substrate for saprophytic fungi. This way, these decomposing agents play a very important environmental role along with other organisms, complementing the cycling of plants and animals. Simultaneously, they produce multiple enzymes that degrade complex substances that allow the absorption of soluble substances used for their own nutrition (Chang, 1993).

Trufem (1999) and Matheus and Okino (1999) highlight the importance of fungi in the context of biotechnology, where they are widely used in the food industry, pharmaceutical industry, bioremediation, in biosorption (removal of heavy and radioactive metals), in agriculture as arbuscular mycorrhizal fungi (AMF), where they are used in techniques that help the development of plants of economic interest, biological control, xenobiotics biodegradation, bioremediation of the soil, treatment of industrial effluents and bioconversion of lignocellulosic residues.

One of the most important processes from an economic point of view is the use of fungi in the conversion of lignocellulosic residues in edible mushrooms by fungus X substrate interaction, enabling the solid fermentation process, through enzymatic system of these microorganisms (Matheus and Okino, 1999).

The cultivation of edible mushrooms has become an increasingly important practice in modern society due to the biotechnological process of bioconversion of various residues in edible mushrooms or in dietary supplements of high nutritional value, enabling a more efficient utilization of materials, besides, it can reduce the volume of waste or accelerate the decomposition process. This way, the residual substrate obtained from the cultivation of edible mushrooms can also be used as soil conditioner, natural fertilizer, or food for animals, closing the exploitation cycle of raw materials (Miles and Chang, 1997), which today is called "zeri" technology, trying to get the maximum use of such material, eliminating the residue of the residue (Chang, 2003).

Productivity and Nutritional Composition of *Lentinus strigosus* (Schwinitz)

microorganisms that can use this substance for their nutrition (Mason, 1980).

fungi (Miles and Chang, 1997).

to understand its physiology.

sources of organic nitrogen.

**2.4.2 Nitrogen** 

Fries Mushroom from the Amazon Region Cultivated in Sawdust Supplemented with Soy Bran 233

compounds such as lipids and proteins can also be used. Approximately 50-60% of the dry weight of wood is made of cellulose; 10-30% of hemicellulose and 20-30% of lignin. Cellulose, which is attacked by both brown-rot fungi as well as white-rot fungi, is made up of glucose molecules. On the other hand, the hemicellulose consists of molecules of arabinnose, galactose, mannose, xylose and uronic acids. The lignin has a more complex structure and has not yet been fully described, being basically units of phenyl-propane with a benzene ring bonded to a hydroxyl group and one or two metoxilic groups. The links in this molecule are highly resistant to chemical degradation. Therefore, there are few

In relation to the degradation of wood and other lignocellulosic materials, it is generally known that the most efficient natural decomposers of lignin are the white rot-fungi, which are mostly the basidiomycets. This name comes from the white color that wood acquires in advanced stages of degradation (Capelari, 1996). Such organisms degrade cellulose, hemicellulose and lignin, but the lignin is preferentially attacked and these are the only organisms able to metabolize the molecule of lignin in CO2 and water (Zadrazil, 1978). The degradation is derived from the excretion of enzymes metabolized through the hyphae of

As a typical white-rot fungi, with decomposing activities of wood, the fungus studied in this work: *Lentinus strigosus*, grows in nature, in favorable conditions, and produces mushrooms through the degradation of the wood substrate or any substrate containing cellulose. From this degradation, the fungi can absorb the nutrients needed for their development and reproduction. The success of mushroom production depends on the understanding of the biology of the fungus and how the environment can influence its growth and development. The domestication of a strain is not a very easy task, when trying to reproduce in the laboratory the ideal conditions for its development, which requires preliminary tests to try

Although wood is the natural substrate for fungi, this substrate does not have a high nitrogen content, and this is necessary for the synthesis of all nitrogen compounds (proteins, purines, pyrimidines and the cell wall chitin of the fungus). The main sources are: salts of ammonia, nitrate, urea nitrogen, and organic compounds like amino acids (Miles and

It should be taken into account that when using a salt as a source of nitrogen, there is the release of the ion that integrates the substrate molecules, and this can change the pH of the medium if it is not metabolized at the same rate as nitrogen, since an accumulation of this ion will take place. The same phenomenon occurs when other salts are used as a supplement. Therefore, the various species and strains may respond differently to the addition of these supplements. Urea, ammonia phosphate, tartarate of ammonia and potassium nitrate, apparently are those with best results according to a research carried out by Maziero (1990). Peptone provides better growth of the fungus when compared with other

Some authors (Rangaswami et al., 1975; Ginterová and Lazarová, 1987) cited by Maziero (1990), argued that *Pleurotus* has the ability to fix atmospheric nitrogen into organic compounds, because some experiments conducted with pasteurized substrates showed that the total nitrogen content has increased. Kurtzman (1979), cited by Maziero (1990) however, discussed the improbable ability of an eukaryote organism to fix nitrogen. The author

Chang, 1997). However, the need for nitrogen by wood-rot fungi is not very great.
