ABSTRACT
This investigation was conducted to study the productivity and bio-safety of Pleurotus ostreatus fruit bodies cultivated on Hydrochloric acid (HCl)-induced oil palm bunch (OPB) substrate. Percentage solutions (0.1-0.5%) HCl were used to induce changes on the initial pH (10.1) of 1400g of OPB replicated 7 times; to 8.2, 7.8, 7.4, 7.1, 6.1 and control (9.0) respectively. One way analysis of variance (ANOVA) was adopted for data analysis using SPSS version 20.1. Means were separated by Duncan Multiple Range Test (DMRT) at p≤0.05%. Fruiting was delayed (19days) in 0.5%HCl substrate while control fruited after12 days. 24 Wistar albino rats made into six groups of four (4) replications, were administered 500ml/kg aqueous extract of mushroom at 24hr interval, for 21days. 0.5% substrate induced the highest (1799.10g/kg) fruit body yield, number (705) and biological efficiency (137.97%) while control produced the lowest (865g/kg, 424 and 61.79.3%). Fruit bodies from 0.2% HCl OPB substrate had the highest mean cap diameter (7.75±0.29cm), stipe length (3.00±0.12cm) and Weight (9.02±0.79g) while those of 0.1% (5.96±0.23cm), 0.4% (2.44±0.07cm) and 0.1% (5.23±0.52g) had the lowest. Fruit bodies from 0.4% had the highest (16.72±0.57mg/100g) vitamin B1 content among other levels while the lowest concentrations of vitamins A and E were observed at all levels. Phenolics were highest at 0.1% (188.96±6.01%) but lowest at (0.2% (106.56±1.76%). Tannins increased from 101.06% in fruit bodies from 0.2% - 134.68 in those of 0.5% substrate groups, unlike other levels. Alkaloids were highest at 0.2% (46.87±0.43%) and terpenoids at control. Moisture (9.07±0.15%) and Protein (24.98±0.03%) contents were highest at 0.5%HCl while control (80.09±0.09%) had the highest carbohydrate. Ash, ether extract (E.E) and crude fiber (CF) were low across all treatment levels and control. Sodium (149.85±6.32) and potassium (5.07±0.46mg/100g) were highest in mushrooms of 0.5%HCl while Chlorine and Calcium tend to increase with increase in percentage HCl. Concentrations of Zinc (181.07±1.22mg/100g) and Iron (197.70±20.01mg/100g) were highest in 0.1% HCl while those of Selenium, Lead and Copper were among the lowest. No mortality was recorded among the animals used. Rats of 0.2 (690.00±13.54 ×109/L) and 0.3% (13800.00±115.47×109/L) groups had the highest white and red blood cells. Highest platelets count of 237.50±23.94 ×109/L was recorded in the control, 0.1 and 0.5%HCl groups. 0.1, 0.4 and 0.5% groups had the highest level of haemoglobin while 0.4(42.25±1.32%) and 0.5% (42.00±0.82%) groups had the highest packed cell volume. Liver function test showed that 0.3HCl group had the highest aspartate aminotransferase AST (37.08±1.36IU/L) and alkaline phosphatase (ALT) (29.71±3.68IU/L) levels while control had the highest alanine aminotransferase (ALP) (23.90±1.15 IU/L). Albumin and Bilurubin levels were not affected by the mushroom extract while Urea and serum protein levels of 0.1 (35.83±1.31 mmol/L) and 0.3%HCl (6.00±0.16 mmol/L) groups had the highest. GSH, GPx, MDA, SOD and catalase were not significantly affected at all levels (0.1-0.5%) groups. Both In vitro and In vivo bio-safety studies were not significant (p ≥ 0.5), suggesting that the mushrooms could be safe for human consumption. Oil palm bunch should therefore be adopted in the commercial production of the Oyster mushroom.
TABLE
OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table of Contents vi
List of Tables xi
List
of Figures xii
List
of Plates xiii
Abstract xiv
CHAPTER
1: INTRODUCTION
1.1 Life
Cycle of Mushroom 1
1.2 Taxonomy 3
1.3 Economic Importance of Oyster Mushrooms 4
1.3.1 Nutritional and food values 4
1.3.2 Medicine/tonic 6
1.3.3 Income and job creation 6
1.4 Justification of Study 7
1.5 Statement
of the Problem 8
1.6 Specific
Objectives 9
CHAPTER
2: LITERATURE
REVIEW
2.1 Mushroom and Food Security 11
2.2 Effect of pH on Mushroom Fruit Body
Formation 12
2.3 Substrates used in Mushroom Cultivation 13
2.4 World Mushroom Production 17
2.5 World Mushroom Market 21
2.6 Important Mycochemicals in Mushroom 22
2.7 Mushroom
Toxicity 25
2.8 Toxic
Effect of Poisonous Mushrooms 27
2.9 Case
Reports on Mushroom Poisoning 33
2.10 Heavy
Metal Uptake by Mushrooms 38
2.11 Bioaccumulation in Mushrooms 39
2.12 Tissue and Organ Responses to Toxins 39
2.12.1 Effect of toxic substances
on the liver 39
2.12.2 Toxic effects of plants on
the liver 43
2.12.3 Effect of toxic substances
on the kidneys 45
2.12.4 Alkaline phosphatase (ALP)
concentration 49
2.12.5 Albumin concentration 50
2.12.6 Uric acid concentration 50
2.12.7 Urinary protein 51
2.12.8 Hematological parameters
and relationship with diseases 51
2.12.8.1 Blood cells 51
2.12.8. 2 Red blood cells (RBC) 52
2.12.8.3 White blood cells (WBC)/leucocytes 54
2.12.8.4 Pack cell volume (PCV) 57
2.12.8.5 Packed cell volume (PCV) hemoglobin (Hb)
levels 57
2.11.8.6 Platelets count 58
CHAPTER
3: MATERIALS AND METHODS
3.1 Study Area 59
3.1.1 Mushroom cultivation 59
3.2 Source of Spawn Culture 59
3.2.1
Spawn production/multiplication 59
3.2.2 Substrate preparation 60
3.3 Determination of Substrate pH 60
3.4 Experimental Design 60
3.5 Substrate
Inoculation 60
3.6 Measurement of Morphological Characters 61
3.6.1 Stipe size of fruit bodies 61
3.6.2 Cap diameter 61
3.6.3 Effect of substrates on fruit body number of
the mushrooms 61
3.7 Yield
and Biological Efficiency 61
3.8 Sample
Preparation 62
3.9 In Vitro Assay 62
3.9.1
Proximate analysis 62
3.9.1.1
Determination of crude protein 62
3.9.1.2
Determination of moisture content 62
3.9.1.3
Determination of ash contents 63
3.9.1.4
Determination of carbohydrate (CHO) 63
3.9.1.5
Determination of ether extract 63
3.9.1.6
Determination of crude fibre 64
3.9.2
Determination of vitamins 64
3.9.2.1
Determination of vitamin A (retinol) 64
3.9.2.2
Determination of vitamin B1 (thiamin) 65
3.9.2.3
Determination of vitamin B3 (niacin) 65
3.9.2.4
Determination of vitamin C (ascorbic acid) 66
3.9.2.5 Determination of vitamin K
(phylloquinone) 66
3.9.2.6 Determination of vitamin E
(tococpherol) 67
3.9.3
Determination of percentage bioactive compounds 68
3.9.3.1
Determination of phenolics content 68
3.9.3.2
Determination of tannins 69
3.9.3.3 Determination of sterols 69
3.9.3.4
Determination of alkaloids 70
3.9.3.5 Determination of terpenoids 70
3.9.3.6 Determination of glycosides 70
3.9.4
Determination of minerals 71
3.9.5
Determination of heavy metals 72
3.10 In Vivo Assay 72
3.10.1
Preparation of aqueous extract of P.
ostratus 72
3.10.2 Experimental animals 72
3.10.3 Determination of LD50 73
3.10.4 Grouping of animals 74
3.10.5 Measurement of body weight 74
3.10.6
Administration of the extract 74
3.10.7 Preparation
of animals for sacrifice 74
3.10.8
Determination of haematological parameters 74
3.10.8.1 Red blood cell (RBC)/erythrocyte count (x109/L) 74
3.10.8.2 White
blood cell (WBC)/ leucocyte count (×109/L) 75
3.10.8.3 Platelets
count (x109/L) 76
3.10.8.4 Determination of packed cell volume
(PCV) (%). 77
3.10.9 Liver
functioning test 77
3.10.9.1 Determination
of aspartate aminotransferase (AST) (IU/L) 77
3.10.9.2 Determination
of serum alanine aminotransferase (ALT) activity (IU/L) 77
3.10.9.3 Determination
of serum alkaline phosphatase (ALP) activity (IU/L) 78
3.10.9.4 Determination
of serum bilirubin 79
3.10.9.5 Determination
of serum albumin 80
3.10.9.6 Determination
of serum total protein 80
3.10.10 Kidney tests 81
3.10.10.1 Determination
of urea (mmol/L) 81
3.10.11
Determination of enzymatic antioxidants and catalase 83
3.10.11.1 Estimation of reduced glutathione (GSH) 83
3.10.11.2 Estimation of glutathione peroxidase (GPx) 84
3.10.11.3 Estimation
of extent of lipid peroxidation (malondialdehyde/MDA) 85
3.10.11.4 Estimation of superoxide dismutase (SOD) 85
3.10.11.5 Estimation of catalase 86
3.11 Statistical
Analysis 87
CHAPTER
4: RESULTS AND DISCUSSION
4.1 Results 88
4.2 Discussion 118
4.2.1 pH variations in substrate and formation of
mushroom fruit bodies 118
4.2.2 Morphological characteristics of fruit
bodies 119
4.2.3 Productivity and biological efficiency of P. ostreatus fruit bodies 120
4.2.4 In
vitro assay 121
4.2.4.1 Vitamins concentrated
(mg/100g) of P. ostreatus fruit
bodies 121
4.2.4.2 Bioactive compounds
concentration of the fruit bodies 122
4.2.4.3 Proximate composition of
fruit bodies 124
4.2.4.4 Minerals concentration of
fruit bodies 125
4.2.4.5 Heavy metals concentration
of fruit bodies 126
4.2.5 In
vivo assay 128
4.2.5.1 Acute toxicity test 128
4.2.5.2 Effect of mushroom extract
on the hematological parameters 128
4.2.5.3 Effect of mushroom extract
on the liver 131
4.2.5.4 Serum protein concentration 134
4.2.5.4 Effect of mushroom extract
on kidney function 134
4.2.5.4.1 Serum urea concentration 134
4.2.5.5
Effect of mushroom extracts on antioxidant enzymes
and catalase 135
CHAPTER 5: CONCLUSION AND RECOMMENDATIONS
5.1 Conclusion 138
5.2 Recommendations 139
References 141
Appendices 165
LIST OF
TABLES
1.1. Some recognized mushroom toxins with
specific/deadly effects 32
4.1. pH of substrates and fruiting duration of P. ostreatus 88
4.2. Morphological characters of fruit bodies 89
4.3.
Productivity and biological
efficiency of fruit bodies 90
4.3.1. Vitamins
concentration (mg/100g) of fruit bodies 91
4.4. Phytochemical (%) compounds composition of
fruit bodies 93
4.5. Proximate composition (%) of fruit bodies 95
4.6. Minerals concentration (mg/100g) of fruit
bodies 97
4.7. Heavy metals concentration (mg/100g) of
fruit bodies 98
LIST OF FIGURES
4.1.
Effect of HCl on the WBC count in albino rats 100
4.2.
Effect
of HCl on the packed cell volume (PCV) level 101
4.3 Effect
of HCl on the red blood cell (RBC) level 102
4.4. Effect
of HCl on the haemoglobin (HB) levels 103
4.5. Effect
of HCl concentration on the platelets level 104
4.6. Effect
of HCl on the AST levels in the liver 105
4.7. Effect
of HCl on the alanine aminotransfarase (ALT) level 106
4.8. Effect
of HCl on the ALP levels in the liver. 107
4.9. Effect
of HCl on the albumin level 108
4.10. Effect of HCl on the T. bilirubin Level 109
4.11. Effect of HCl on the D. bilirubin Level 110
4.12. Effect of HCl on the urea level in the kidney. 111
4.13. Effect
of HCl on the serum protein level. 112
4.14. Effect of HCl on the glutathione (GSH) level 113
4.15. Effect of HCl on the glutathione peroxidase (GPx) level. 114
4.16. Effect of HCl on the MDA levels 115
4.17. Effect of HCl on the superoxide dismutase (SOD) level 116
4.18. Effect of HCl on the catalase level 117
LIST OF PLATES
1 Uncolonized
spawn substrate 163
2 Fully
colonized spaw 163
3 OPB
substrate 163
4 Fruit
bodies from different groups 163
5 C. cinerius contaminated OPB 164
6 Ground
fruit bodies 164
7 Dried
fruit bodies 164
8 Collection
of samples from rats 164
CHAPTER
1
INTRODUCTION
Mushrooms belong to the class
Basidiomycota and order Agaricales. They do not possess chlorophyll like
green plants; for manufacturing their food but for their growth and development,
they require pre-formed food like smaller broken down molecules of lignin,
cellulose and starch (Banjo, 1998).
Chang, (1999) defined mushroom as “a macro-fungus with a distinctive fruiting
body which can either be epigeous (growing on or close to the ground) or
hypogenous (growing under the ground)”. The macro-fungi have fruiting bodies
large enough to be seen with unaided eye and to be picked up by hand. Ideally,
the word mushroom refers only to the fruit body of a macro-fungus. Unlike green
plants, mushrooms are heterotrophs and without chlorophyll, they cannot
generate nutrients by photosynthesis, but instead take already made nutrients
from organic materials. Most mushroom species are either under the
Basidiomycota or Ascomycota; the two phyla are under the kingdom Fungi (Cho,
2004).
1.1 LIFE CYCLE OF MUSHROOM
The
life cycle of a mushroom may be traced from a spore, which under favorable
condition germinates to form a mass of branched hyphae of mycelium which
colonizes a substrate. This represents the vegetative stage of its growth. When
a given substrate is fully colonized, the vegetative growth ceases. Typically
some hyphae form primordia or fundament which is the beginning of the reproductive
stage (Bahl, 1985). This develops
further to differentiate into stipe (stalk) and the pileus (cap) of the fruit
body, which when mature exposes the gill, tissue or generative tissue on the
underside, from which spores are liberated, so that the life cycle is
perpetuated.
Many
fungi that form mushroom exist in mycorrhizal with trees and this is one of the
reasons why the forest is often the target for mushroom hunters. Many have
learnt through the ages, by trials and error, to identify the edible and
inedible mushrooms. In many cases some inedible ones resemble the edible types
and are eaten without adverse effect (Takama et al.,
2010). However, there have been occasional
accidents of consuming poisonous species leading to death or serious illness.
Mushrooms
have now been recognized universally as food and are grown on commercial scale
in many parts of the world including Nigeria. The growing and consumption
interest of oyster mushroom is increasing largely due to its taste, medicinal
and nutritional properties (Garcha et al.,
1993).
Oysters
are naturally found on rotten wood materials. Takama et al., (2010) observed
that this fungus is common in Nigeria and often found growing around the
African breadfruit tree (Treculia africana).
In Nigeria, the most prized edible species are Pleurotus, Termitomyces,
Tricholoma and Volvariella (Ambali
et al.,
2008).
Pleurotus
species, commonly known as oyster
mushrooms, are edible fungi cultivated worldwide especially in south East Asia,
India, Europe and Africa. China produces 64% of all edible mushrooms in the
world and 85% of all oyster mushrooms all over the world (Pleurotus spp.)
is also produced in China (Chang, 1999). Oyster mushrooms are the third largest
commercially produced mushroom in the world (Obodai et al., 2003); however, Sánchez, (2010) reported that P.
ostreatus is the second largest, next to Agaricus bisporus in the
world market. Mushroom cultivation is the fifth largest agricultural sector in
China with 24 billion USD value and 10% growth rate every year for the last 30
years (Zhang et al., 2014).
Large
volumes of unused lignocellulosic by-products are available in tropical and
sub-tropical areas. These by-products are left to rot in the field or are
disposed-off through burning. Utilizing these by-products for mushroom
cultivation using locally available technologies may be one of the solutions to
transforming these inedible wastes into acceptable edible biomass of high
market value.
1.2 TAXONOMY
Pleurotus
ostreatus is
an edible white rot fungi (WRF) commonly known as the Indian Oyster, Phoenix
Mushroom, or the Lung Oyster. It is classified as follows:
Kingdom Mycota
Division Basidiomycota
Class Agaricomycetes
Order Agaricales
Family Pleurotaceae
Genus Pleurotus
Species P. ostreatus
(Jacq.Ex.Fr)
P. Kumm
Species
of Pleurotus have been recorded and new species are discovered more or
less frequently although, some of these are considered identical to previously
recognized species. The genus Pleurotus, which was first recommended as
a tribe within genus Agaricus by Fries, (1821), was proposed as a genus
by Quelet, (1886). Three genera of this group, Pleurotus, Lentinus,
and Panus, were possible to be separated according to the anatomic
characters of the sterile tissues of the hymenophores as being homogeneous taxonomic
groups. Hilber, (1982) recommended that crossing of mono-spore cultures is a
valuable basis for Pleurotus studies. Pleurotus pulmonarius (Jacq:
Fr.) Kummer is the most cultivated species among the oyster mushroom and the
type species of the genus Pleurotus. Recently, the majority of
mycologists have followed the proposition made by Singer, (1986) which divides
the genus Pleurotus into six sections: Sect. Lepiotarii (Fr.)
Pilat, Sect. Calyptrati Sing., Sect. Pleurotus Sing., Sect. Coremio,
Pleurotus (Hilber), Sect. Lentodiellum (Murr.) Sing. and Sect. P. tuberegium
Sing.
1.3 ECONOMIC
IMPORTANCE OF OYSTER MUSHROOMS
The economic
importance of oyster mushrooms can be described based on the following.
1.3.1 Nutritional and
food values
The
desirability of a food product does not necessarily bear any correlation to its
nutritional value, instead, its appearance, taste and aroma which sometimes,
can stimulate ones appetite (Chang, 2013). In addition to nutritional value,
mushrooms have some unique colour, taste, aroma and texture characteristics
which attract their consumption by humans (Sabir et al., 2003).
Mushrooms
are consumed for nutritional as well as their food values (Agraher-murugkar and
Subbulakshmi, 2005). Pleurotus spp. are
among the edible mushrooms consumed in the tropical states of West Africa and
it is used as substitutes for meat and fish in some cases (lwalokun et al., 2007). Apart from being known
for their appetizing flavour, they also offer themselves as potential protein,
minerals and vitamins sources (Wahlid et
al., 2006; Chang, 2013). 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 (Parkayastha and
Nayak, 2002; Chang and Miles 2004; Kurtzman, 2009). Mushrooms contain
appreciable quantities of crude fibres, although little information exists on
the total dietary fibre (TDF) contents of mushrooms. Crude fibre content values
reported by many authors suggest that mushrooms are potential sources of
dietary fibre (Kurasawa et al., 1982;
Furlani, 2014). Okwulehie et al., (2008)
reported high crude protein and carbohydrate contents in P. ostreatus var florida fruit bodies cultivated on different
substrates and substrate supplementations.
According to
Okhuoya and Okogbo, (1991), Okwulehie and Odunze, (2004a), mushrooms generally
contain low oil and fat, and are therefore recommended as good supplements for
patients with cardiac problems.
The vitamins
content of many mushrooms have been investigated and results of such
investigation show that they are rich in vitamins including Thiamine,
Riboflavin, Ascorbic acid, Ergosterine and niacin (Okwulehie and Odunze, 2004a;
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 not a
misdirection (Aletor, 1995). Fasidi and Kadiri, (1990), and Fasidi, (1996) have
also reported that tropical mushrooms are rich in mineral nutrients and
carbohydrates.
In Nigeria, P. tuber-regium is used as both food and
medicine. The sclerotium which is hard is peeled and ground for use in local
cuisines (Okhuoya et al., 2010). The
mushroom itself is simply chopped and used in soups or may be dried for future
use (Okhuoya and Okogbo, 1990). Wermer and Beelman, (2002) reported that there
has been a trend toward discovering ways of treating mushrooms so as to give
them added value. For example, mushrooms enriched in selenium are now grown
commercially.
1.3.2 Medicine/tonic
For
the past 20 years, interests in medicinal aspects of mushrooms have greatly
been stimulated by the large number of scientific studies conducted on
mushrooms (Tricita, 2004). Some kinds of mushrooms
such as Amanita muscaria had been
reported to produce intense excitement and hallucination to the consumer
(Kandler, 1983; Oei, 1996; Royse, 1996). Mushroom has also been reported as therapeutic food useful
in preventing diseases such as hypertension, hyper-cholesterolemia and cancer.
These functional characteristics are mainly due to their chemical composition
(Manzi, 1999b). Owing to the tolerance of P. pulmonarius to high
temperature, it has been reported that its speedy fruiting and yield
efficiencies attract many cultivators to the mushroom industry (Trudell and
Ammirati, 2009). Using modern approaches, scientists have
isolated and identified specific components that can either destroy or at least
debilitate three of mankind’s killer diseases: Cancer, heart disease and
HIV/AIDS (Tricita, 2004). 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;
Tricita, 2004). Mushrooms have been used as anti-tumour, anti-cancer and for many
other therapeutic purposes (Liu et al.,
2001; Chang and Miles, 2004).
1.3.3 Income and job creation
Growing
mushrooms is labour intensive and for countries where jobs are scarce, Oyster
mushrooms cultivation can create jobs, both in semi-urban and rural areas
(Won-sik, 2004). Tricita, (2004) reported that some technologies can use family
labour, thus providing all members of the family with employment. He went
further to say that the labour of out-of-school youths and even school children
can also be utilized especially as the bagging of substrates and related
operations can be easily done by children.
Mushroom
growing is also recommended as a project in a co-operative, where division of
labour is practiced, one group will do the substrate preparation and still
another group maybe engaged in spawn production and still another group can
take charge of growing condition management (Tricita, 2004).
1.4 JUSTIFICATION OF STUDY
Using modern approaches, scientists
have isolated and identified from mushroom, specific components that can either
destroy or at least debilitate three of mankind killer diseases: cancer, heart
disease and HIV/AIDS (Tricita, 2004). Research has also proved that some
mushroom species are highly medicinal and are found to reduce cholesterol,
inhibit tumor counteract Pernicious anaemia etc (Rambelli and Menini, 1983;
Stamets, 1993; Oei, 2003). Apart from their potentials for medicines, mushrooms
are also good source of protein, minerals and vitamins (Walid et al., 1988).
Available records show that mushroom
industry is a multi-billion Dollar enterprise in many countries of the world
especially, the developed nations. This has also created and provided
employment to out-of-school youths and even to school children (Oei, 2003;
Tricita, 2004).In spite of this global trend in mushroom production, most
edible mushrooms are still being collected from the wild in many localities in
Nigeria.
Oil palm bunch (OPB) is one of the
most abundant organic materials often seen as waste around homes and palm oil
mills. Even though, people living in most rural communities have used it to
produce soap of very low market quality, other importance of it are yet to be
fully harnessed. The incorporation of oil palm bunch in mushroom cultivation and
other waste management strategies will no doubt boost food security and
employment opportunities.
1.5 STATEMENT OF THE PROBLEM
pH
is an important factor for good production of oyster mushrooms. Most mushrooms
grow and perform well at pH near to neutral or slightly acidic at 6.1 and 7.5
respectively (Khan et al., 2013). The ongoing awareness on
mushroom as a valuable source of protein with low cholesterol content which
over rides meat and other fatty foods, may soon diminish due to the
fore-scarcity of sawdust which serves as major substrate for its commercial
production (Quimio et al., 1990; Jonathan et al., 2012c).
Oil
palm bunch has reportedly contributed high level environmental degradation
especially around oil palm mills and other areas where palm oil is commercially
processed. To safeguard our environment, oil palm bunch must be put to adequate
use, either by transforming it into alternative economically important product
or through biological degradation which mushroom is capable of doing.
However,
many growers of oyster mushroom have experienced difficulties in growing Pleurotus ostreatus using oil palm
bunch. Achufusi, (2016) used oil palm bunch as a substrate for the cultivation
of P.
ostreatus, the substrate was contaminated by Corprinus cinerius (a competitor mushroom that contaminates mushroom
bed) and observed no yield of P.
ostreatus fruit bodies in the substrate and its supplementations. The
substrate pH was later found high at 10.3 and was suggested as the reason for Corprinus contamination and no yield of P .ostreatus.
In
a large scale production, Oyster mushroom growers prefer to use lime (CaCO3)
as an alkaline buffer to optimize pH of some acidic substrates to increase
mushroom production and maximize profit, but a suitable acid buffer to optimize
the pH of highly alkaline substrates such as OPB has not been well understood
by experts.
Many
questions have been raised on the consumption safety of P. ostreatus if grown on Hydrochloric acid (HCl) induced-OPB as a
means of optimizing its pH for better yield of mushrooms; since Mycophobia (ie, irrational fear of consuming
fungi such as mushrooms) is a major problem facing mushroom consumption in
Nigeria (Kalu et al., 2013).
In
Nigeria, proper documentation of mushroom toxicity is rare, as most reports on
toxicity or death in humans associated with mushroom consumption are under
reported. Besides, several new syndromes are being described in mushroom
poisoning (Diaz, 2005), which calls for their continuous toxicological
evaluation.
In view
of possible toxicity of P. ostreatus fruit bodies grown on HCl mediated
Oil Palm Bunch (OPB), the need for both in
vitro and in vivo toxicological
screening of the mushrooms become pertinent.
1.6 SPECIFIC OBJECTIVES
The
main objectives of this experiment are to:
i. Determine
the effect of HCl on the pH of oil palm bunch (OPB)
ii. Determine
the yield and Biological efficiency of P.
ostreatus cultivated on HCl induced OPB.
iii. Evaluate
the effect of HCl on the morphological characteristics of P. ostreatus fruit bodies.
iv. Determine
the nutritional, vitamins, phytochemicals and heavy metals composition of the
mushroom fruit bodies.
v. Assess
the in vivo bio-safety of the P. ostreatus fruit bodies
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