CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND
Chang and Miles (1992) defined mushroom as a macrofungus with a distinctive fruiting
body, which can be either epigenous (growing on or close to ground) or hypogenous
(growing under the ground) and large enough to be visible to the naked eye and to be picked
up by hand. Thus, mushrooms need not be only basidiomycetes, or aerial or fleshy, or edible.
Mushrooms can be ascomycetes, grow underground, have a non-fleshy texture and need not
be edible (Chang, 2008).
Mushrooms are widespread in nature and since earliest recorded history; humans have
viewed them as a special kind of food, savoring the delicious flavours and acknowledging the
nutritional value of this special group of fungi (Chang and Buswell, 1996). Mushrooms have
long been appreciated for their flavour and texture, and some for medicinal and tonic
attributes. However, recognition that they are nutritionally a very good food and
physiologically an important potential source of biologically active compounds of medicinal
value is much more recent (Chang, 1996). It is now known that mushrooms are rich in high
quality protein, contain a high proportion of unsaturated fatty acids and have a nucleic acid
content low enough to allow daily use as a form of vegetable (Chang, 1996). Moreover,
latter-day application of modern analytical techniques has, in a number of cases, provided a
scientific basis for assigning medicinal value through the identification of various mushroomderived
compounds including anti-cancer, anti-viral, immunopotentiating,
hypocholesterolaemic and hepatoprotective agents (Liu et al., 1995). For example, the
pharmacological activities of Ganoderma lucidum have been attributed mainly to triterpenes
and polysaccharides produced by the mushroom. Several polysaccharides and protein-bound
polysaccharides with immune-modulating and anti-tumour activities have also been isolated
from a variety of mushrooms (Chang, 1996).
Agricultural production and the agro-food industry furnish large volumes of solid wastes,
residues and by-products, produced either in the primary agro-forestry sector (crop-based) or
by secondary processing industries (processing-based) with the major part being
lignocellulosic biomass (Philippoussis and Diamantopoulou, 2011). Recently, Zhang (2008),
reviewing the global world information about lignocellulose availability estimated the
production of lignocellulosic biomass to be more than 200x109 tonnes per year. The amount
of crop residues produced annually in the world from 27 food crops is estimated at about
4x109 tonnes (Lal, 2008). The majority of this organic matter poses an environmental
pollution problem.
In nature, mushrooms have not only been a source of food for man and other animals, but
also have played an important role in the cycling of carbon and other elements through the
breakdown of lignocellulosic plant residues and animal dung, which serve as the substrates
for these saprophytic fungi (Chang, 1996). In this way, mushroom species, as agents of decay
help keep the environment from being overwhelmed by the dead organic debris of plants and
animals. Mushroom forming fungi are therefore amongst nature’s most powerful
decomposers, secreting strong extracellular enzymes due to their aggressive growth and
biomass production (Adenipekun, 2009). They have the capability to produce a wide range of
enzymes that can break down complex substrates into simpler soluble substances and absorb
them for their growth and development (Oei, 1991).
Strong consumer demands and threats of depletion of mushrooms have stimulated increased
worldwide production in the past few decades (Chang and Miles, 2004). The increased
demand for mushrooms is due to their unique culinary and medicinal properties (Yan et al.,
2003). Commercial cultivation of mushrooms as a source of food, nutriceutical and medicine
is now a worldwide industry with over 120 countries contributing to a crop which, in 1999
totalled 4.3 million tonnes (Chang and Miles, 1991). Several reports indicate that commercial
production of fresh edible mushrooms is a rapidly growing industrial activity. In 2002, world
production of cultivated mushrooms was estimated to be 12,250 thousand tonnes and was
valued at about US$ 32 billion, whereas mushroom products used mainly for dietary
supplements were assessed to have generated about US$ 11 billion (Chang, 2006).
Mushroom cultivation is an efficient and relatively short biological process of food protein
recovery from lignocellulosic materials (Martinez-Carrera et al., 2000). The cultivation of
edible mushrooms has become an increasingly important practice in modern society due to
the biotechnological process of bioconversion of various residues into edible mushrooms or
in dietary supplements of high nutritional value, enabling a more efficient utilization of waste
materials. Interestingly, the spent compost that remains after harvesting mushrooms may still
be recycled for use as animal feeds and soil conditioner. Earlier studies have demonstrated
that spent compost of both Volvariella and Pleurotus had increased crude protein content
compared with raw straw (Quimio, 2004).
Mushroom production can be a lucrative cottage industry for low-income rural households in
developing countries (Ferchak and Croucher, 1996). The activity is labour intensive and can
provide full or part-time employment. A small mushroom production
1.0 INTRODUCTION
1.1 BACKGROUND
Chang and Miles (1992) defined mushroom as a macrofungus with a distinctive fruiting
body, which can be either epigenous (growing on or close to ground) or hypogenous
(growing under the ground) and large enough to be visible to the naked eye and to be picked
up by hand. Thus, mushrooms need not be only basidiomycetes, or aerial or fleshy, or edible.
Mushrooms can be ascomycetes, grow underground, have a non-fleshy texture and need not
be edible (Chang, 2008).
Mushrooms are widespread in nature and since earliest recorded history; humans have
viewed them as a special kind of food, savoring the delicious flavours and acknowledging the
nutritional value of this special group of fungi (Chang and Buswell, 1996). Mushrooms have
long been appreciated for their flavour and texture, and some for medicinal and tonic
attributes. However, recognition that they are nutritionally a very good food and
physiologically an important potential source of biologically active compounds of medicinal
value is much more recent (Chang, 1996). It is now known that mushrooms are rich in high
quality protein, contain a high proportion of unsaturated fatty acids and have a nucleic acid
content low enough to allow daily use as a form of vegetable (Chang, 1996). Moreover,
latter-day application of modern analytical techniques has, in a number of cases, provided a
scientific basis for assigning medicinal value through the identification of various mushroomderived
compounds including anti-cancer, anti-viral, immunopotentiating,
hypocholesterolaemic and hepatoprotective agents (Liu et al., 1995). For example, the
pharmacological activities of Ganoderma lucidum have been attributed mainly to triterpenes
and polysaccharides produced by the mushroom. Several polysaccharides and protein-bound
polysaccharides with immune-modulating and anti-tumour activities have also been isolated
from a variety of mushrooms (Chang, 1996).
Agricultural production and the agro-food industry furnish large volumes of solid wastes,
residues and by-products, produced either in the primary agro-forestry sector (crop-based) or
by secondary processing industries (processing-based) with the major part being
lignocellulosic biomass (Philippoussis and Diamantopoulou, 2011). Recently, Zhang (2008),
reviewing the global world information about lignocellulose availability estimated the
production of lignocellulosic biomass to be more than 200x109 tonnes per year. The amount
of crop residues produced annually in the world from 27 food crops is estimated at about
4x109 tonnes (Lal, 2008). The majority of this organic matter poses an environmental
pollution problem.
In nature, mushrooms have not only been a source of food for man and other animals, but
also have played an important role in the cycling of carbon and other elements through the
breakdown of lignocellulosic plant residues and animal dung, which serve as the substrates
for these saprophytic fungi (Chang, 1996). In this way, mushroom species, as agents of decay
help keep the environment from being overwhelmed by the dead organic debris of plants and
animals. Mushroom forming fungi are therefore amongst nature’s most powerful
decomposers, secreting strong extracellular enzymes due to their aggressive growth and
biomass production (Adenipekun, 2009). They have the capability to produce a wide range of
enzymes that can break down complex substrates into simpler soluble substances and absorb
them for their growth and development (Oei, 1991).
Strong consumer demands and threats of depletion of mushrooms have stimulated increased
worldwide production in the past few decades (Chang and Miles, 2004). The increased
demand for mushrooms is due to their unique culinary and medicinal properties (Yan et al.,
2003). Commercial cultivation of mushrooms as a source of food, nutriceutical and medicine
is now a worldwide industry with over 120 countries contributing to a crop which, in 1999
totalled 4.3 million tonnes (Chang and Miles, 1991). Several reports indicate that commercial
production of fresh edible mushrooms is a rapidly growing industrial activity. In 2002, world
production of cultivated mushrooms was estimated to be 12,250 thousand tonnes and was
valued at about US$ 32 billion, whereas mushroom products used mainly for dietary
supplements were assessed to have generated about US$ 11 billion (Chang, 2006).
Mushroom cultivation is an efficient and relatively short biological process of food protein
recovery from lignocellulosic materials (Martinez-Carrera et al., 2000). The cultivation of
edible mushrooms has become an increasingly important practice in modern society due to
the biotechnological process of bioconversion of various residues into edible mushrooms or
in dietary supplements of high nutritional value, enabling a more efficient utilization of waste
materials. Interestingly, the spent compost that remains after harvesting mushrooms may still
be recycled for use as animal feeds and soil conditioner. Earlier studies have demonstrated
that spent compost of both Volvariella and Pleurotus had increased crude protein content
compared with raw straw (Quimio, 2004).
Mushroom production can be a lucrative cottage industry for low-income rural households in
developing countries (Ferchak and Croucher, 1996). The activity is labour intensive and can
provide full or part-time employment. A small mushroom production
