ABSTRACT
Four organic wastes; mahogany (Khaya ivorensis) sawdust (MSD), Gmelina aborea sawdust (GSD), oil palm fruit fibre (OPFF) and oil palm empty fruit bunch (OPEFB) were evaluated for their effects on growth, yield, quality and protein content of Lentinus squarrosulus (Mont.) Singer. Plastic bag technology was used with treatments replicated ten times and arranged using a completely randomized design. The quality of the harvested mushrooms was evaluated on the basis of four pileus diameter size groups (>7 cm, 5-7 cm, 3-5 cm, <3 cm) and a deformed group; while their protein analyses were carried out using Kjeldahl’s method. Results on mushroom growth showed that oil palm fruit fibre (OPFF) took the least time for full mycelial colonization and the longest time occurred on Gmelina sawdust (GSD). Analysis of variance showed that there were significant differences (P < 0.05) in the time required for primordia initiation of mushrooms grown on oil palm empty fruit bunch (OPEFB), oil palm fruit fibre (OPFF) and Gmelina sawdust (GSD). Results on mushroom yield revealed that mean fresh weights of harvested mushrooms varied from 4.12 ± 0.16 g on oil palm empty fruit bunch (OPEFB) to 16.05 ± 0.68 g on mahogany sawdust (MSD). There were significant differences (P < 0.05) in the biological efficiency of mushrooms grown on mahogany sawdust (MSD), Gmelina sawdust (GSD) and oil palm empty fruit bunch (OPEFB). Mahogany sawdust produced the highest quality mushrooms, with 26% in the >7 cm group while Gmelina sawdust (GSD) and oil palm empty fruit bunch (OPEFB) had none in the same quality group. The percentage protein content of harvested mushrooms ranged from 13.27% for mushrooms produced from mahogany sawdust (MSD) to 27.42% for those grown on oil palm fruit fibre (OPFF). The above findings reveal the possibility of commercial production of high quality L. squarrosulus on oil palm fruit fibre (OPFF) and mahogany sawdust (MSD) while oil palm fruit fibre (OPFF) is recommended as the best substrate for spawn production among the various organic wastes used in this study.
INTRODUCTION
CHAPTER ONE
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 mushroom- derived 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 200×109 tonnes per year. The amount
of crop residues produced annually in the world from 27 food crops is estimated at about
4×109 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 business can be
established with low capital investment and with minimal requirements for space and equipment.
Mushroom production represents an important opportunity for developing countries, particularly Nigeria, since innovations in cultivation and post-harvest processing make possible new opportunities (Ferchak and Croucher, 1996).
1.2 Problem Statement
Nigeria by virtue of her population size generates several tonnes of agricultural, industrial, municipal and domestic wastes that overwhelms the nation’s waste disposal machinery and pose an environmental pollution problem (Okhuoya et al., 2010). These so called wastes constitute a negative factor both in the economic evaluation of existing industrial and agricultural operations and because of the adverse environmental effects resulting from their disposal. Sadly, much of this waste is either burned, shredded or used as landfill or for improvement of soil quality, even though these wastes constitute a potentially valuable resource and can be recycled for the production of edible food for man (Chang, 1996).
Much of the cellulose in nature is bound physicochemically with lignin. Because lignin is highly resistant, it protects cellulose against attack by most microbes, and it must be degraded by chemical or biological means before the cellulose can be utilized (Salvagi and Kaulkarnis,
2001). The use of the polysaccharides in the lignocellulosic complex is also limited due to their high lignin content (Hadar et al., 1992). Zadrazil and Grabbe (1983) reported that about one-half the total production of plant residues from agriculture and industrial processes remains unused and burdens the environment. Chang (1989) also noted that all agricultural production from crop plants generated enormous waste, because little of each crop was actually used; typically 80-90% of the total biomass of agricultural production is discarded as waste and this is because only part of the organic matter synthesized through photosynthesis every year is directly edible in the form of fruits, vegetables and food grains.
The handling and disposal of these lignocellulosic residues are often problematic due to their chemical structure and decomposition properties (Philippoussis et al., 2001). However, various problems associated with the practical utilization of these materials have not yet been solved (Taniguchi et al., 2005). One of the key problems hindering the effective utilization of these renewable resources as raw materials for the production of food and feeds is the low susceptibility of lignocellulose to hydrolysis, which is attributable to the crystalline structure of cellulose fibrils surrounded by hemicellulose and the presence of the lignin seal which prevents penetration by degrading enzymes (Chahal and Chahal, 1999).
Although physical and chemical technologies may, in some cases, play important associated roles for handling these wastes. Biotechnological approaches are essential for the emergence of practical conversion processes which can be applied to situations in developing countries throughout the world where large scale capital intensive operations are inappropriate. Adequate food-intake is one of the fundamental human requirements, but there is no denying the fact that millions of people especially in the developing countries of Africa, Asia and Latin America are beset with danger of their very survival due to its non-availability. The greatest difficulty in feeding humans is to supply a sufficient quantity of the body building protein (Chang, 2008). In Africa, the gap between the increasing population and supply of protein is somewhat wide since the traditional sources of protein have not kept pace with population growth. In view of the general shortage of animal protein in the developing countries, the need to explore vegetable protein as an alternative source has been duly recognized.
An FAO/WHO joint expert group on protein requirement reviewed evidence on the effects of protein malnutrition on the predisposition of adults and children to infection, on reduced stature and retarded psychomotor developments in adults malnourished in younger years. They also observed reduced birth weight and difficulty in recovering from surgery trauma and other pathological states (Chang, 2008).
Foodstuffs of plant origin such as cereals, vegetables, potatoes and cassava constitute an important dietary source of protein for many segments of the world’s population particularly where animal protein is not only in short supply but have become costly and beyond the reach of middle and poor classes. One of the major disadvantages of these types of foodstuffs is their low protein contents. As the shortage of high quality protein is at its peak in the developing countries like Nigeria, there is need to supplement these diets with unconventional sources of protein.
1.3 Justification
Huge quantities of a wide variety of organic wastes are generated annually through the activities of the agricultural, forest and processing industries. Therefore, there is considerable pressure nowadays to develop biotechnological processes for the rational treatment and/or disposal of these vast quantities of waste lignocellulosic materials generated annually (Buswell et al., 1996). Of the various approaches adopted, one of the most significant in terms of producing a higher value product from the wastes is the cultivation of edible mushrooms by solid state fermentation (Chang and Miles, 1991). Reports have shown that
various lignocellulosic residues from agro-industrial sector, such as oil palm and timber wastes among others, can provide the mushroom with nutrients required for spawn run and fructification which under controlled conditions and procedures result in an optimum product yield (Fung et al., 2005).
Mushrooms are a nutritious food source being rich in protein, vitamins and minerals. Earlier reports have shown that mushrooms are rich in ascorbic and amino acids, and protein is their most abundant nutrient (Fasidi and Kadiri, 1990; Aletor, 1995). The food and agricultural organization (FAO) recognizes mushrooms as food contributing to the protein nutrition of the countries which depend largely on cereals because of their high protein quantity and quality (Kuforiji and Fasidi, 2009). They are also known to contain substances that enhance the immune system, fight infectious diseases, and lower blood pressure and cholesterol levels. The fact that mushrooms, a novel source of protein offer a promising way of alleviating protein malnutrition in developing countries in the nearest future cannot be denied.
In addition, Nigeria by virtue of its vantage tropical location is one of the world’s potential hotspots for various forms of biological resources including mushroom (Akpaja et al., 2003). Currently, the exploitation of indigenous Nigerian mycoresources is still over-shadowed by the preponderance of green plants (Okhuoya et al., 2010). Vigorous researches on these easily over looked forest members might evolve an accidental source of drugs that would resolve the world’s cancer, AIDS and leukemia problems (Okhuoya et al., 2010).
1.4 Objectives of the Study
To determine the effects of different local organic wastes on the growth and yield of Lentinus squarrosulus.
To evaluate the market quality of Lentinus squarrosulus cultivated on the different organic wastes.
To estimate the protein content of the mushrooms grown on different local organic wastes.
This material content is developed to serve as a GUIDE for students to conduct academic research
EFFECTS OF DIFFERENT ORGANIC WASTES ON THE GROWTH YIELD MARKET QUALITY AND PROTEIN CONTENT OF LENTINUS SQUARROSULUS (MONT.) SINGER AN EDIBLE NIGERIAN MUSHROOM>
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