ABSTRACT
Cultivation of mushrooms using agricultural residues provides a very cheap and environmentally friendly alternative for producing foods with high nutritional value. This study was conducted to determine the influence of different straw substrates and cropping container on the yield, nutritional, phytochemical and polysaccharide degrading potentials of Pleurotus ostreatus. Six sample substrates: Andropogon gayanus, Zea mays and Pennisetum purpureum straws and their combinations were used. Known weight of each substrate and substrates combinations were made in 3 replications and placed into two and half (2.5) litres perforated and non-perforated transparent plastic buckets. Experiment was laid out in a Completely Randomized Design (CRD). Data analysis was carried out using one way analysis of variance (ANOVA) while mean separation was done by Duncan Multiple Rang Test (DMRT). Results showed that P. ostreatus grown on Andropogon gayanus substrate in non-perforated (Non-perf AND) buckets gave the highest (580.11g/kg and 96.69%) yield and biological efficiency (BE %) respectively. Results of yield and BE% of P. ostreatus with respect to substrate combinations showed P. ostreatus grown on combined Pennisetum and Zea mays in non-perforated buckets (Non-perf.PEN/ZEA) gave the highest yield (573.66g/kg) and BE% (95.61%) respectively. The overall result on yield and BE% indicated that A. gayanus straw substrate supported highest yield (1040.66g/kg) and BE% (86.72%) respectively. Results of proximate analysis showed that P. ostreatus is a good source of crude protein, fat, dietary fibre and carbohydrates. The highest crude protein (26.58+0.00%) was recorded in A. gayanus, fat (8.50%) in combined Andropogon and Zea mays straw, fibre (8.50%) in combined Andropogon and Zea mays straw and carbohydrates (44.95%) in combined Pennisetum and Zea mays. The result of the vitamin analysis clearly shows that P. ostreatus grown on these substrates are very rich in vitamins and other nutrients hence regarded as good quality food materials. The result of the phytochemicals analysis showed that the mushrooms contained moderate amount of alkaloids, tannins, flavonoids, saponins and phenols. P. ostreatus showed high polysaccharide degrading potentials on all the substrates compared to fresh/unused substrates suggesting its importance in environmental management strategies. Therefore the use of Andropogon gayanus straws in non- perforated plastic buckets or trays should be adopted in the commercial production of P. ostreatus fruit bodies.
TABLE
OF CONTENTS
Title
Page i
Declaration ii
Certification iii
Acknowledgement iv
Table
of Content v
List
of Tables vii
List
of Plates viii
Abstract ix
CHAPTER
1
BACKGROUND
OF THE STUDY
1.1.
Introduction 1
1.2 Ecology of Mushroom 2
1.3 Categories of Mushrooms 3
1.3.1 Edible mushrooms 3
1.3.2. Poisonous mushrooms 3
1.4. Oyster
Mushrooms (Pleurotus species) 4
1.5 Pleurotus ostreatus (Jacq) P.Kumm 5
1.6 Economic
Importance of Mushrooms 5
1.6.1 Nutritional
and food values of mushrooms 5
1.6.2 Medicinal values of mushroom 7
1.6.3 Reducing environmental
pollution 9
1.6.4 Income and job creation 11
1.7 World Mushroom Production
and Consumption 11
1.8 Justification 14
1.9 Aims
and Objective 16
CHAPTER 2
LITERATURE REVIEW
2.1 Mushroom
Cultivation 17
2.2 Nutritional
Composition of Cultivated Mushrooms 26
2.3 Mushroom
and Substrate-polymer Degradation 28
CHAPTER 3
MATERIALS AND
METHODS
3.1 Source of Spawn 30
3.2 Location
of Study 30
3.3 Experimental Design 30
3.4 Spawn
Multiplication 30
3.5 Substrates
and their Preparation 31
3.6 Inoculation
of Substrates 32
3.7 Pileus Diameter and Stipe Length of Fruit
Bodies Measurement 32
3.8 Determination
of Yield and Biological Efficiency 32
3.9 Sample
Preparation 34
3.10 Proximate
Analysis 35
3.10.1 Determination
of crude protein 35
3.10.2 Determination of moisture content 36
3.10.3 Determination of the ash content of fruit bodies 36
3.10.4 Determination of crude (dietary fibre) 37
3.10.5 Determination of the carbohydrate content of the
sample 38
3.10.6 Determination of fats and oils 38
3.11 Determination of Mineral Content of the Dry Samples
of the Mushroom 39
3.12
Determination of the Amount of Phytochemicals
Contents in the Mushroom Fruit-bodies 39
3.12.1 Determination of alkaloids 39
3.12.2 Determination of flavonoids 40
3.12.3 Determination of phenol content 40
3.12.4 Determination of saponins 41
3.12.5 Determination of tannins 42
3.13. Determination of Vitamin Content of the Dry Samples 42
3.13.1 Determination of Vitamin A (Retinol) 42
3.13.2 Determination of Vitamin B1 (Thiamin) 42
3.13.3 Determination of Vitamin B2
(Riboflavin) 43
3.13.4 Determination of Vitamin B3 (Niacin) 43
3.13.5 Determination of Vitamin C (Ascorbic Acid) 43
3.14 Substrate Analysis 44
3.14.1 Cellulose 44
3.14.2 Hemicellulose 44
3.14.3 Lignin 44
3.15 Statistical Analysis 45
CHAPTER
4
RESULTS
AND DISCUSSION
4.1 Results 46
4.2 Discussion 64
CHAPTER 5
CONCLUSION/RECOMMENDATION
5.1 Conclusion 77
5.2 Recommendation 77
REFERENCES 79
LIST OF TABLES
4.1:
Comparison between yield and biological efficiency of P. ostreatus fruit
bodies harvested from perforated and non-perforated buckets across various
substrates.
4.2:
Comparison between yield and biological efficiency of P. ostreatus fruit
bodies harvested from perforated and non-perforated containers across substrate
combinations
4.3: Influence of substrate on the yield and
biological efficiency of P. ostreatus
fruit bodies
4.4: Proximate
composition of fruit-bodies of Pleurotus
ostreatus cultivated on different substrates and substrate combinations
4.5: Mineral content
(mg/100g) of fruit-bodies of Pleurotus
ostreatus cultivated on different
substrates and substrate combinations
4.6:
Vitamin composition of fruit-bodies of Pleurotus
ostreatus cultivated on different
substrates and substrate combinations
4.7: Phytochemical
composition of fruit bodies of Pleurotus
ostreatus cultivated on different
substrates and substrates combinations
LIST OF FIGURES
4.1:
Effect of bucket perforation on the cap size of Pleurotus ostreatus cultivated on Andropogon, Zea mays and Pennisetum straw substrates
4.2:
Effect of bucket perforation on the stipe length of Pleurotus ostreatus cultivated on Andropogon, Zea mays and Pennisetum straw substrate
4.3: Effect of bucket perforation on the fresh
weight of Pleurotus ostreatus
cultivated on Andropogon, Zea mays and Pennisetum straw substrate
4. 4: Lignocellulosic
content of fresh and spent substrate
4.5: Percentage reduction
in lignocellulosic content of the substrates after mushroom cultivation
LIST OF PLATES
1: Spawn multiplication
2: Fruit- bodies growing from
non-perforated buckets
3: Fruit-bodies growing from perforations
on buckets
CHAPTER
1
1.1. INTRODUCTION
Mushrooms are macro-fungi with a
distinctive fruiting- body which can be either epigeous (growing on or close to
ground) or hypogenous (growing under the ground), large enough to be seen with
the naked eye and be picked with hand (Chang and Miles, 2004). 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). Ideally, the word mushroom refers only to the fruit-body.
Mushrooms can also be defined as the fleshy spore-bearing fruiting-bodies of
fungi, typically produced above ground, on soil, decaying substrates and wood
logs (Okwulehie and Nosike, 2015).
They lack chlorophyll unlike green plants
and consequently cannot use solar energy to manufacture their food. Their mode
of nutrition is by producing a wide range of extracellular enzymes that can
break down complex substrates after which they are able to absorb the soluble
substances so formed (Chang and Miles, 2004; Song, 2004). Mushroom lack true
roots, they anchor into the substrates by their tightly interwoven thread-like
hyphae, which also colonize the substrates, degrade their biochemical
components and take up the hydrolysed organic content for their own nutrition
(Chang, 2013).
Mushrooms reproduce by spores or mycellia fragments.
Under favourable conditions, spores germinate into germ tube which develop into
hyphae collectively called mycelia. Germinated germ tube form primary mycelia
and then secondary mycelia through (plasmogamy) in which the cytoplasm of two
parent cells fuses together without the fusion of nuclei, effectively bringing
two haploid nuclei close together in the same cell (Oei, 2003). They absorb
nutrients from the substrate upon which they grow and colonize the substrate.
When stimulated by temperature or humidity the mycelia colony forms pinheads
under certain conditions that grow and become fruit-bodies and finally
differentiate into a pileus (cap) and stipe (stalk) called mushroom. Under the
cap, spores are produced in the basidia. Fruit-bodies release the spores in
order to produce the next generation (Oei, 2003; Song, 2004).
The life cycle of mushroom is divided into
two phases: vegetative and reproductive phases. Vegetative phase indicates
linear growth of fungal mycelium breaking down complex substrate components
into simpler molecules and absorbing them as nutrients. Under low temperature, high
humidity, high oxygen tension and high light intensity, the mycelia ceases
vegetative growth and begin to produce fruit bodies which are called
“mushroom”. This is the reproductive growth phase.
There are about 1.5 million scientifically
identified species of fungi, estimated 10,000 species produce fruit-bodies
called mushrooms. More than 3000 species are edible of which only about 100 are
cultivated commercially (Chang and Miles, 2004).
1.2
ECOLOGY OF MUSHROOM
Mushrooms are widespread in nature and
they remain the earliest form of fungi known to mankind (Okhuoya et al., 2010). Ecologically, macro-fungi
can be classified into three groups: the saprophytes (degrading already dead
materials), the symbiotic mycorrhizal species (living together with other
organisms especially trees in a close, mutually beneficial relationship) and
the parasitic species living at the expense of other organisms. Most
terrestrial macro-fungi are saprobes or mycorrhizal symbionts, but some are
pathogen of plants (Mueller, 2007).
The issue of fungal diversity, its extent
and conservation has attracted more attention in the last 10 to 15 years than
in any period of history (Hawksworth, 2004). Mushrooms appear to be collected
and consumed almost the entire year, but most mushrooms are collected during
the rainy seasons, suggesting the importance of rainfall patterns in mushroom
phenology (Dijk et al., 2003). Such
is the case in tropical Africa, where many species are found in the rainy
seasons, but there are a few species that are present throughout the year
(Adekunle and Ajao, 2005)
1.3
CATEGORIES OF MUSHROOMS
1.3.1
Edible mushrooms
Edible mushrooms are fleshy and are
consumed for their nutritional value. Edibility may be defined by criteria that
include absence of poisonous effects on humans and desirable taste and aroma
(Mattila et al., 2001). Edible
mushrooms include many fungal species that are either harvested wild or
cultivated. For a long time, wild edible mushrooms have played an important
role as a human food (Chang and Miles, 2004). They are used extensively in
cooking in many cuisines. They are known as the “meat” of the vegetable world
(Hass and James, 2009). Many of the edible mushrooms grow in Nigerian forests
and farm lands (Okwulehie et al.,
2008).
1.3.2.
Poisonous mushrooms
Some mushroom species have been
characterized as hazardous to health and defined as toxic species. These are
mushrooms which when ingested, may result to health disorder or even death. The
toxins
present are secondary metabolites
produced in specific biochemical pathways
in the fungal
cells. Mushroom poisoning
is usually the result of ingestion
of wild mushrooms after misidentifying toxic mushroom as an edible species. The
most common reason for this is close resemblance in terms of colour and general
morphology
of the toxic mushrooms species with edible species (Karlson-Stiber and Persson,
2003).
A
wide variety of toxic mushrooms belong to different genus Amanita which produces toxin called amatoxin.
The
family Amanitaceae (genus Amanita) is
well known as having many toxic species. Amatoxins are present in species of Amanita genus such as: Amanitaphalloides, A. virosa, A. verna, A. ocreata, A. bisporigera, A. suballiacea, A.
tenuifolia and A. hygroscopica.
Other toxins also found in Amanita spp.
are phallotoxin and virotoxin. The species A.
phalloides is responsible for the majority of the fatalities caused by
mushroom poisoning. The toxic effects are caused by phallotoxin and amatoxin
(Wong and Ng, 2006). Other poisonous mushrooms mainly belong to genus Inocybe, Cortinarius, Panaeeolus and Russula (Berger and Guss, 2005).
1.4. OYSTER
MUSHROOMS (PLEUROTUS SPECIES)
Pleurotus is the scientific name for oyster
mushrooms and is grown worldwide, and China is the major producer. It has been
regarded as one of the most profitable cash crops in Korea, accounting for 65%
of total domestic mushroom production (OECD, 2005). Pleurotus spp (Oyster
mushrooms) are one of the most popular edible mushrooms and belong to the genus
Pleurotus and the family Pleurotaceae
(Sturion and Otterer, 1995). The oyster mushroom is the second most important
mushroom in production in the world, accounting for 25% of total world
production of cultivated mushrooms (Kang, 2004). All oyster mushrooms belong to
the class Basidiomycetes, subclass Hollobasidiomycetidae, order Agricales and
family Pleurotaceae. Like any other mushroom, they could be found in the wild
or cultivated artificially by mushroom farmers (Alexopolous et al., 1996).
To date approximately 70 species of Pleurotus have been observed and new
species are discovered more or less frequently although some of these are
considered identical with previously recognized species (Irie et al., 2001). Oyster mushroom is
regarded as one of the commercially important edible mushrooms throughout the
world. It consists of a number of different species including Pleurotus ostreatus, Pleurotus sajor-caju,
Pleurotus cystidiosus, Pleurotus florida, Pleurotus pulmonarius, Pleurotus
tuber-regium, Pleurotus citrinopileatus and Pleurotus flabellatus. Pleurotus
species efficiently utilizes their substrate (Fermor et al., 2000).
Pleurotus species have been eaten by human
all over the world for their nutritional value, medicinal properties and other
beneficial effects. Oyster mushrooms are good source of dietary fiber and other
valuable nutrients. They also contain a number of biologically active compounds
with therapeutic activities (Mane et al.,
2007). Pleurotus species are rich
source of proteins, minerals (Ca, P, Fe, K and Na) and vitamin C, B complex
(thiamine, riboflavin, folic acid and niacin) (Çağlarırmak, 2007). They are
consumed for their nutritive as well as medicinal values (Agrahar-Murugkar and
Subbulakshmi, 2005).
1.5 PLEUROTUS OSTREATUS (JACQ) P.KUMM.
Among the genera of Pleurotus, P. ostreatus is the most popular and widely cultivated in different
regions of the world. Mushroom farmers usually make millions of dollar from
this single species (Jonathan et al.,
2008). P. ostreatus is cultivated in
tropical, subtropical and temperate regions of the world (Okwulehie et al.,
2008). This mushroom has ability to grow on varieties of agro-industrial wastes
(Shah et al., 2004; Jonathan and
Adeoyo, 2011).
P. ostreatus is preferred more than other Pleurotus species because of its delicious
taste; and high quantities of proteins, carbohydrates, minerals (calcium,
phosphorus, iron) and vitamins (thiamin, riboflavin and niacin) as well as low
fat (Manzi, et al., 1999; Kurtzman,
2005).
1.6 ECONOMIC
IMPORTANCE OF MUSHROOMS
1.6.1
Nutritional and food values of mushrooms
Mushrooms are widespread in nature
and since earliest recorded history; humans have viewed them as a special kind
of food, savouring the delicious flavours and acknowledging the nutritional
value of this special group of fungi (Chang and Buswell, 1996). They are
consumed for their nutritive as well as medicinal values (Agrahar-Murugkar and
Subbulakshmi, 2005). In addition to nutritional value, mushrooms have some
unique colour, taste, aroma and texture characteristics which attract their
consumption by humans (Chang, 2003; Sabir et
al., 2003).
Cultivated and wild mushrooms contain
reasonable amount of proteins, carbohydrates, minerals, fibers and vitamins
(Olei, 1996; Stamets, 2000). Furthermore, mushrooms are low in calories,
sodium, fats, and cholesterol (Chang, 1996). Mushroom protein is intermediate
between that of animals and vegetables but superior to most other foods
including milk and contains all the nine essential amino acids required by man
(Chang and Miles, 2004; Kurtzman, 2009). FAO recognizes mushrooms as the right
source of protein to fight protein malnutrition in the cereal dependent
developing countries (FAO, 2004). Okwulehie et
al. (2008) reported high crude protein and carbohydrate contents in fruit-bodies
of P. ostreatus var. florida
cultivated on different substrates.
Mushroom generally contains low fats
and oil content and these make them suitable food supplements for patients with
cardiac problems (Okwulehie and Odunze, 2004; Chang, 1996). Mushrooms are called
the diabetics delight because they are low-calorie, high protein diet, with no
starch and sugars (Kar and Gupta, 2001).
Mushrooms contain appreciable quantities of
crude fibers, although little information exists on the total dietary fiber (TDF)
contents of mushrooms. Crude fiber content values reported by many authors
suggest that mushrooms are potential sources of dietary fiber (Sloan, 2001).
With very high fiber and
alkaline elements, mushrooms are suited to those suffering from hyperacidity
and constipation; consumption of fiber has gained importance in general health
maintenance (Burton et al., 1995).
Mushrooms are important source of vitamins.
The vitamins of group B are abundant as well as other vitamins (Mattila et al, 2001). The vitamin content of
many mushrooms have been investigated and results of such investigation shows
that they are rich in vitamins including thiamine, riboflavin, ascorbic acid,
ergosterine, pyridoxine, folic acid and niacin (Okwulehie and Odunze, 2004;
Chang, 2013). Since vitamins are essential in the diet of man, and conventional
sources of vitamins are scarce in recent times. It is pertinent therefore that
attempts made to increase the list of the sources of cheap vitamins is a good
idea (Aletor, 1995).
1.6.2
Medicinal values of mushroom
Mushrooms have long been appreciated for
their flavour and texture and some for medicinal and tonic attributes. Edible
mushrooms once called the “food of the gods” and still treated as a garnish or
delicacy can be taken regularly as part of the human diet or be treated as
healthy food or as functional food. The extractable products from medicinal
mushrooms, designed to supplement the human diet not as regular food, but as
the enhancement of health and fitness, can be classified into the category of
dietary supplements and mushroom nutriceuticals (Chang and Buswell, 2003).
Dietary supplements are ingredients extracted from foods, herbs, mushrooms and
other plants that are taken without further modification for their presumed
health-enhancing benefits (Chang and Miles, 2004). The considerable
pharmacological activities of mushrooms make them to be of interest in
pharmaceutical industries for the development of drugs (Okwulehie, et al., 2008).
Mushrooms have long been used as a
valuable food source and as traditional medicines around the world, especially
in Japan and China. The most recently introduced medicinal mushroom is Ganoderma spp. Its fruiting body has
traditionally been used for medicinal purposes and for thousands of years has
been regarded by Chinese to be high quality herbal medicine (Oei, 2003).
Records of health promoting properties such as antioxidant, antimicrobial,
anticancer, cholesterol lowering and immune-stimulatory effects have been
reported for some species of mushrooms (Anderson, 1992; Mizuno, 1999; Mau et
al., 2004). The United States National Cancer Institute has chosen
mushrooms as a source of new drugs for the treatment of cancer (Liu, 1993) and
the ethno-medicinal value of many edible mushrooms have been reported by many
researchers (Asuqo and Etim, 2011). There
has been an increasing interest in mushroom as a source of biologically active
compounds which provide to humans medicinal or health benefit such as the
prevention and treatment of diseases (Rathee et al., 2012). Bioactive
compounds can be found in mushroom as cell wall components such as
polysaccharides and proteins or as secondary metabolites such as phenolic
compounds, terpenes, steroids, glycol lipids, fatty acid derivatives,
nucleosides and many other substances of different origins (Wasser, 2002;
Mizuno, 1999). Most of these bioactive compounds derived from mushrooms are
known to function as biological response modifiers (BRM). Biological response
modifiers are substances that stimulate the body's response to infection and
disease. The body is known to produce these substances but not in appreciable
quantity hence, exogenous supply through diet or dietary supplements are
needed. Mushroom nutraceuticals may unarguably be the source of this exogenous
supply because edible mushrooms are known to be safe and devoid of undesirable
side effects. Most bioactive compounds which play essential roles in human and
animal physiology have been found in many mushrooms.
According to Okwulehie and Odunze
(2004), Auricularia auricular, Pleurotus squarraosulus and Russula spp. have been found to contain
appreciable amounts of alkaloids, phenols, saponins and flavonoids. Alkaloids
have powerful effects in animal physiology and are of interest in
pharmaceutical industries for compounding drugs (Edeoga and Eriata, 2001).
Alkaloids are stimulants and act by prolonging the action of many hormones
(Rambelli and Menini, 2000).
Flavonoids have been reported to be
useful in the treatment of some physiological disorders and diseases.
Flavonoids have been reported to have anti-oxidant properties and are used as
anti-carcinogens and ageing substances (Hilang and Feraro, 2002). In a similar
way, flavonoids are said to have anti-bacteria functions (Dokara, 2006).
In the last 3 to 4 decades,
some Nigerian scientist had been able to carry out some well-structured studies
on the medicinal properties of mushrooms found in Nigeria. The use of these mushrooms varies from one ethnic group
to the other. Ethno mycological uses of edible and medicinal mushroom by the
Yoruba people of South West Nigeria had been reported (Alabi, 1990). Moreover,
reports of the ethno medicinal uses of mushroom by the Igbos in South East and
the Igalas in north central Nigeria had also been reported by Akpaja et al.
(2003) and Ayodele et al. (2009) respectively. Information gathered
include ethno medicinal uses of the following mushrooms: Pleurotus
tuber-regium, Lentinus squarullosus, Termitomyces microcarpus, Calvatia cyathiformis,
Ganoderma lucidum, G. resinaceum, G. applanatum, Schizophyllum commune,
Volvariella volvaceae, and Deldinia concentrica. For instance, P.
tuber-regium is used for alleviating headache, stomach pain fever, cold,
constipation; L. squarullosus for mumps, heart diseases; T. microcarpus
for gonorrhea; C. cyathiformis for leucorrhea, bareness; G.
Lucidum for treating arthritis, neoplasia;
G. resinaceum is used hyperglycemia, liver diseases
(hepatoprotector); G. applanatum used as antioxidant and for diabetes (Okhuoya,
et al., 2010; Fasidi and Olorunmaiye,
1994).
The effects of aqueous extract of Ganoderma
lucidum collected from Zaria, Nigeria on blood glucose levels of
normoglycemic and alloxan induced diabetic wistar rats had been reported by
Mohamed et al. (2007). Oyetayo (2006) reported the hypolipidemic
properties of two tropical edible mushrooms Pleurtotus tuber-regium and Termitomyces
clypeatus in altering the plasma levels of some lipids in male albino rats
fed high fat diets. Antimicrobial property of several mushrooms had also been
reported (Jonathan and Fasidi, 2003; Ezeronye et al., 2005; Ofodile et al., 2008; Oyetayo, 2009).
1.6.3 Reducing environmental
pollution
Reducing environmental pollution is by
bioconversion of vast quantities of organic wastes into mushrooms. Organic
solid wastes are a kind of biomass, which are generated annually through the
activities of the agricultural, forest and food processing industries. They
consist mainly of three components: cellulose, hemicellulose and lignin. The
general term for these organic
wastes is lignocellulose. It is a common knowledge that lingo-cellulosic wastes
are available in abundance both in the rural and urban areas (Chang and
Buswell, 2003).
Agricultural production and the
agro-food industry produce 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 lingo-cellulosic biomass (Philippoussis and Diamantopoulou, 2011).
Recently, Zhang (2008), reviewing the global world information about
lignocellulose availability estimated the production of ligno-cellulosic
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 ligno-cellulosic
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).
Mushroom cultivation is an effective
bioconversion technology of transforming wastes and woods into potentially
valuable resources. Mushroom cultivation could also be an important part of
sustainable agriculture and forestry (Qiu, et
al., 2008). It has been revealed recently that mushroom mycelia can play a
significant role in the restoration of damaged environments (Quimio et al.,
1990). Saprotrophic, endophytic, mycorrhizal, or even parasitic fungi/mushrooms
can be used in mycorestoration, which can be performed in four different ways:
mycofiltration (using mycelia to filter water), mycoforestry (using mycelia to
restore forests), mycoremediation (using mycelia to eliminate toxic waste, and
mycopesticides (using mycelia to control insect pests). These methods represent
the potential to create the clean ecosystem, where no damage will be left after
fungal implementation (Stamets, 2005).
1.6.4
Income and job creation
Since mushroom cultivation can be a
labour-intensive agro-industrial activity, it could have great economic and
social impact by generating income and employment for both women and youth,
particularly in rural areas in developing countries (Chang, 1999). Total
employment in the mushroom industry in China was over 30 million people in
2006, with only 10 percent of the employed being actual mushroom farmers, other
employment fall within sectors such as food, beverage manufacturing, trading
and management, transport, marketing, wholesale, retailing, export etc (Beteez
and Kustudia, 2004).
The local mushroom industry can also be the
main source of revenue for local government (Wasser, 2002). Mushrooms
cultivation practices have paramount importance in food self-sufficiency
attempts (Diriba et al., 2013), specially for low-income countries like
Nigeria. Mushroom farming is very lucrative;
most especially because of the demand for it by foreigners in Nigeria
(Onebunne, 2014). Mushrooms can generate additional employment and income
through local, regional and national trade offering opportunities through
processing enterprises (FAO, 2009).
1.7 WORLD MUSHROOM PRODUCTION AND
CONSUMPTION
Mushrooms represent one of the
world`s greatest untapped resources of nutritious food. Unfortunately, it is
realized that mushrooms did not receive universal acceptance over the years
since a number of naturally growing mushrooms are poisonous (Chang and Buswell,
2008). Total mushroom production worldwide has increased more than 18-fold in
the last 32 years, from about 350,000 metric tons in 1965 to about 6,160,800
metric tons in 1997. The bulk of this increase has occurred during the last 15
years. This is because of a notable shift which has been observed in the
mushroom supply (Royse, 2003). 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 tons (Chang and Miles, 1991).
China is the largest producer and
consumer of mushrooms in the world followed by USA and Netherland. China
produces approximately 70 percent of world mushroom production, and mushroom is
their sixth economically important crop in terms of country’s revenue
generation. The following statistics serve to illustrate dramatic increases in
the production of farmed mushrooms from 1978- 2006, with particular emphasis on
China’s contribution to total world production, given its status as the leading
mushroom producer (Chang, 2006).
Currently, mushroom farming is being practiced in more than 100
countries and its production is increasing at the rate of 7% per annum.
Production of mushroom has already crossed 6 million metric tons annually in
the world and is expected to reach around 7 million metric tons in the next ten
years. Lately there is increased
contribution in mushroom production from Eastern European countries like Poland
and Hungary where mushroom production has received a boost as evident from the
production figures of these countries (NRCM, 2004).
Several reports indicate that
commercial production of fresh edible mushrooms is a rapidly growing industrial
activity. Chang (2013) reported that oyster mushroom cultivation has increased
tremendously throughout the world during the last few decades and rates the
second after Agaricus bisporus
(button mushroom). The world market for the mushroom industry in 2001 was
valued at over $40 billion. Edible mushrooms valued at about US $30 billon and
medicinal mushrooms were worth about US $9-10 billion (Chang, 2006). These
mushrooms are traded mostly in processed form but lately, fresh mushrooms are
being preferred over preserved ones in Europe and American countries (NRCM,
2004). Major exporting countries of fresh mushrooms are Netherlands, Poland,
Ireland and Belgium. In 2002, world production of cultivated mushrooms was
estimated to be 12,250 tons and was valued at about US$ 32 billion, whereas
mushroom products used mainly for dietary supplements were assessed to have
generated about US$ 11 billion (Chang, 2006). The world market for the mushroom
industry in 2005 was valued at over 45 billion US Dollar (Chang, 2006).
Due to increased recognition of mushrooms medicinal and nutritional
values, coupled with the realization of the income generating potential of
mushrooms through trade, the demand for mushrooms has been on the rise. The
edibility of mushrooms depends on the absence of poisonous content and its
desirable taste and aroma. Being a rich source of nutrition and being fat,
cholesterol and gluten free and very low in sodium content; mushrooms are
gaining popularity among health-conscious consumers. The global market for
mushrooms was valued at $29,427.92 million in 2013. This market is projected to
grow at a rate of 9.5% from 2014 to reach $50,034.12 million by 2019. Europe dominated
the market in 2013, and is projected to be the fastest-growing market for
mushrooms between 2014 and 2019, followed by the Asia-Pacific region (FAO,
2014)
The mushroom sub-agricultural sector has not been given adequate
attention in Africa, in spite of all the favourable growth conditions including
substrate availability (Okwulehie and Okwujiako, 2008). This is largely due to
lack of know-how and lack of understanding that mushroom can play vital roles
towards enhancing human health when used as dietary food supplements, lack of
reliable good quality mushroom growers, lack of venture capital to support
mushroom farming entrepreneurs and absence of systematic government support
towards promoting mushroom farming as a valuable cash crop (Chang, 2006). African
nations are seldom listed among the largest producer and exporters of edible
mushrooms and mushroom products in the world (Chang and Miles, 2004).
In Nigeria, a great quality and variety of edible and medicinal
mushrooms are sourced from the wild due to inchoate mushroom farming culture
(Okhuoya et al., 2010). The practice
of mushroom hunting existed for decades spanning generations and mostly
embarked upon by women and children (Okhuoya, 1992). Growers in Nigeria and
Africa at large need potentially higher income to help off-set the increased
risks associated with mushroom production so as to maximize mushroom production
volume on the continent.
1.8
JUSTIFICATION
Several types of containers, ranging
from perforated polyethylene bags, trays, plastic buckets, bottles and wooden
racks have been employed to cultivate mushrooms (Kang et al., 2002; Sharma, 2003).There
has been serious concern on whether growing oyster mushrooms on lateral medium
as in perforated plastic buckets, poly bags etc.; encourage more fruit-body
production than the tray method. Many growers believe that poly bags provide a suitable
growth condition likened to that of tree trunk and supports higher yield
because of acclaimed high surface area. Others say tray method rather provides
more surface area and encourages higher Fruit-body production. The present
investigation is intended to douse the speculations raised above.
Substrate materials employed in mushroom production are usually
by-products from industries, households, agriculture etc. and are usually
considered as wastes. These wastes, if carelessly disposed off in the
surrounding environment by dumping or burning lead to environmental pollution
and consequently cause health hazards. However, they are actually resources in
the wrong place at a particular time.
Mushroom farmers that use the substrates
are only interested in converting dry waste biomass into more biological
efficient production of fresh mushroom fruit-bodies to maximize profit and
achieving waste and production cost reduction.
Mushrooms are a unique biota which assembles their food by
secreting degrading enzymes and decompose the complex food materials present in
the biomass where they grow, to generate simpler compounds which they then absorb
and transform into their own peculiar tissues.
Growing
mushrooms on agro-wastes therefore represents the only modern
economically viable biotechnological process for the conversion of waste plant
residues into protein rich food (mushrooms) and other valuable intermediate or
finished products. Mushrooms cultivation can also be considered as the most economic method of
converting lingo-cellulosic agricultural wastes to consumable, protein rich
biomass. Conversion of lignocellulose into food and feed rich in protein,
vitamins and minerals by mushrooms also offers an alternative means for
developing unconventional sources of man’s daily nutrient requirements. Since
there is enormous waste in the agro-industry; using 25% of the yearly volume of
burned cereal straws in the world for instance, could result in a fresh
mushroom yield of 317 million metric tons (317 billion kg) per year.
Considering
the yearly available world waste in agriculture (500 billion kg), we could
easily reduce them through mushroom cultivation. Hence, wastes emanating from
different agricultural wastes such as banana leaves, spare grass (Imperata cylindrica) straws, husk, pods, pulp, waste paper, sugarcane
bagasse, rice straw, corn cobs etc. can be eliminate through mushroom
production.
Considering the enormous importance of
mushrooms as highlighted above and the variability of the wastes from agriculture
and industries, it will be pertinent to investigate the best of the wastes and
methods that would give the highest quantity and quality fruit-bodies.
Finally,
the huge amounts of lingo-cellulosic biomass can be potentially bio-converted
into different high value raw materials and products such as bio-ethanol,
enriched animal feed, cheap energy sources for microbial cultivation and enzyme
production, biodegradation and bioremediation of toxic organic compounds
through mushroom cultivation thereby reducing the
incidence of pollution of our environment.
1.9 AIMS AND
OBJECTIVES
The aims and objective of this research is
to:
1. Determine the best substrates that would
enhance the morphology and yield of P.
ostreatus fruit bodies
2. Compare the morphology, yield and
biological efficiency of fruit-bodies cultivated on perforated and
non-perforated buckets.
3. Determine and compare the phytochemical
and nutritional compositions of the mushroom fruit bodies cultivated on the
various substrates.
4. Ascertain the extent of polysaccharide
degradation of A. gayanus, P. purpureum
and Z. mays straw substrates by P.
ostreatus.
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