**2.4 Factors inherent to the nutritional needs of the mushroom**

#### **2.4.1 Carbon**

The main source of carbon and energy of a plant tissue, used by fungi for their development, are the polysaccharides and lignin in the cell wall, although other polymeric 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 microorganisms that can use this substance for their nutrition (Mason, 1980).

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 fungi (Miles and Chang, 1997).

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 to understand its physiology.

#### **2.4.2 Nitrogen**

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

Man has constantly realized the nutritional value of mushrooms, as well as their healthy properties compared to other foods, such as red meat, where mushrooms are more advantageous and important as they are great sources of carbohydrates, proteins, mineral salts, vitamins and essential amino acids, which can help to maintain a good nutritional

Nutritional Analyses of mushrooms have shown their importance. They contain more protein than vegetables. Sources of protein such as meat, chicken, have a high level of cholesterol and fat, which are known to cause increase in weight and cardiovascular diseases. For this reason, the proteins from other sources became more popular in recent years, such as proteins from fungi, algae, bacteria and yeast (Lajolo, 1970; Chang and

Studies carried out by Lintzel (1941; 1943), according to Crisan and Sands (1978), indicated that approximately 200 g of mushrooms (dry weight) are sufficient to feed a normal human being weighing approximately 70 Kg, providing a good nutritional balance. Nutritionally, these macrofungi are a good food source. The composition of fats, carbohydrates, vitamins, etc., varies according to species, the cultivation method and also with the substrate used in cultivation (Crisan and Sands, 1978; Przybylowicz and Donoguue, 1990; Bononi et al. 1999;

Mushrooms are excellent foods for the diets, because they nourish and do not accumulate fat in the organism. They are sources of all essential and some nonessential amino acids. They contain minerals like calcium, potassium, iodine, phosphorus and vitamins including thiamine, riboflavin, niacin, and ascorbic acid, and others related to the B complex (Molena, 1986; Miles and Chang, 1997 Bononi et al., 1999). They also have a high unsaturated fat

Mushrooms with larger nutrition index (based on essential amino acid index) have nutritional value similar to meat and milk, while those with a smaller nutrition index compare to some vegetables such as carrots and tomatoes. The nutritional index of these fungi outperforms those of plants and vegetables, except soy (Crisan and Sands, 1978). In general, the protein content of fresh mushrooms is twice higher than cabbage, four times greater than the content of protein of the orange and twelve times that of the Apple (Chang,

Research carried out in India by Garcia, et al. (1993), where the authors compared the nutritional levels of *Agaricus* and *Pleutotus*, revealed the importance of the amino acids of these mushrooms for people that are lacking animal protein, for religious reasons, and whose main food source comes from vegetables and grains usually poor in essential amino acids. Food supplementation with mushrooms is of fundamental importance in the diet of

In addition, there is also a great interest in the cultivation of the mycelium in a submerged condition to obtain flavoring and fragrant compounds of great value to the food industry. For this purpose, the mycelium is grown submerged, using a variety of substrates, according to the type of the desired compound. This flavoring property is characteristic of

The main source of carbon and energy of a plant tissue, used by fungi for their development, are the polysaccharides and lignin in the cell wall, although other polymeric

some lignolitic mushrooms, such as the *Pleurotus* genus (Gurtiérrez et al., 1994)

**2.4 Factors inherent to the nutritional needs of the mushroom** 

balance (Crisan and Sands, 1978; Garcia et al., 1993; Miles and Chang, 1997).

**2.3.1 Nutritional importance** 

Haynes, 1978; Urben et al., 2003).

Miles and Chang, 1997; Andrade, 2007).

content (Miles and Chang, 1997).

1980).

this kind of people.

**2.4.1 Carbon** 

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

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 sources of organic nitrogen.

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

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

and Chang, 1997).

**2.5.1 Temperature** 

in nature (Miles and Chang, 1997).

between 25 and 30 C.

**2.5.2 Moisture** 

Fries Mushroom from the Amazon Region Cultivated in Sawdust Supplemented with Soy Bran 235

range that varies from minimum, maximum, and optimum growth in relation to these physical factors. Certainly these factors are influenced by other factors such as nutrition, medium conditions, genetic characteristics of the strain and mycelial growth stage (Miles

The influence of temperature on mycelial growth and production of fruiting bodies is dependent on the species and strains in question, i.e. there is an ideal temperature for the proper development of the metabolism of the fungus, which is a characteristic of each strain. Nonetheless, there is an interval that varies between 10-40 C, which must be respected, because exceeding these limits, it is going to cause the death of the mycelium (Maziero, 1990). The optimum temperature for growth also varies with the purpose of cultivation. So, the ideal temperature to produce the fruiting body (Miles and Chang, 1997) is different from that intended for the production of metabolic products such as those intended for medicinal compounds as polysaccharides/polypeptides immune-regulatory compounds (PSPC). Temperature extremes are important in determining the survival and dispersion of species

Kaufer (1935), cited by Maziero (1990) cultivated *Pleurotus corticatus* in laboratory and according to their results, the ideal temperature for the growth of mycelium was 27C. Clock et al., (1959) according to Maziero (1990), obtained a good growth of mycelium of *P. ostreatus* in the range of 22-31 C. At 37 C the mycelium still was able to grow, but abnormally, while at 17 C no growth was observed. The lethal temperature for *P.* "florida", *P. ostreatus* and *P. eringii* is 40 C when exposed to more than 24 hours (Zadrazil, 1978). Maziero (1990) studying different strains of *Pleurorus* observed that the better mycelial growth happened

In relation to the emergence of primordia, Block et al. (1959) cited by Maziero (1990) report that the strain of *P. ostreatus* fructified at a 26 C, however at 31 C, although the fruiting body continues to develop, there was no emergence of primordia. For Kurtzman and Zadrazil (1989), the authors must have used in their work, a strain of *P. "florida*" since the

Eira and Minhoni (1997) report that the control of temperature in a cultivation chamber is decisive for a good harvest. For a good growth of the mycelial mass on substrate cultivation, the ideal temperature for *Pleurotus* spp should be between 24 and 26 C. After that the primordia initiation and growth phases start, when the temperature inside the cultivation chamber must be between 15 and 240C, considering that, the lowest are ideal for cultivation of shimeji or *Pleurotus* spp strains that are more demanding and also minimizes the incidence of pests and diseases. According to the same authors, some strains of hiratake usually fructify in hot weather (up to 30 C). For the most demanding strains, temperature and relative humidity control in the chamber of cultivation can be achieved with an automated central air-conditioning associated with a ventilation system, to ensure the ideal

Most fungi require high moisture content. Guzmán et al. (1993) report that fungi have an optimum growth on substrates with 70 to 80% humidity. Urben et al. (2003) cite a good humidity range for *Lentinula edodes* cultivated with Jun-Cao technique between 55-70%. It

fruiting temperature at 26 C is very high, being more appropriate for *P. "florida"*.

climatic conditions for the development of the mushroom.

suggested the hypothesis that the spores of nitrogen fixing bacteria are stimulated to develop during the process of pasteurization of the substrate, generating bacteria responsible for the nitrogen fixation.

Care should be taken to avoid excessive nitrogen supplements, which can inhibit the development of the fungus. Montini (2001) reports that tested substrates with high concentrations of cereal bran inhibited the formation of the mushroom and consequently, the number of cultivated mushrooms *Lentinula edodes* in axenic conditions (cultivation with substrate sterilized and under controlled environmental conditions). In Taiwan, the substrate for cultivation of *Pleurotus* mushroom is prepared with 84% of sawdust, 5% of rice bran, 5% wheat straw, 3% soya bran and 3% calcium oxide (Przybylowicz and Donoghue, 1990).
