Abstract
In order to isolate and identify Rhizopus spp that is associated with the spoilage of bread, laboratory experiments were conducted. The sample of bread used were purchased and kept for 7 days at room temperature in the laboratory to allow the visible growth of organism. The glass wares used for this experiment were sterilized properly in hot air oven at 160oc for two hours; other materials were sterilized by autoclaving at 121oc for 15 mins. The culture media used for this experiment was the sabouraud’s dextrose agar (SDA) which is known to support the growth of only fungal organisms. The mould was inoculated in the sabouraud’s dextrose agar (amphecilin was added to inhibit bacterial growth), incubated at room temperature on bench for four days, after which it was isolated and view on a slide with the aid of lacto phenol cotto blue under the microscope for cultural characteristics. In the experiment a mass of soft closely woven white, cottony and velvet black, greenish and brownish threads were observed. In the microscope examination, non-septate, mass of round black spores, rhizoids were seen and this characterized Rhizopus species and many other fungi, which are Aspergillus spp, Mucor spp, Penicillium spp and Fusarium spp. In conclusion bakery products are more susceptible to Rhizopus spp and contamination may result from poor hygiene of the bread makers or the ubiquitous nature of spores of the organism.
CHAPTER ONE
1.1 BACKGROUND OF THE STUDY
Rhizopus is a genus of common saprophytic Fungi on plants and specialized parasites in animals. They are found on a wide variety of organic substrates, including mature fruits and vegetables (Kirk, et al, 2008), jellies, syrups, leather, bread, peanuts and tobacco. Some Rhizopus species are opportunisticRh agents of human zygomycosis (Fungal Infection) and can be fatal. izopus species grows as filamentous, branching hyphae that generally lack cross-wall (i.e they are coenocytic). They reproduce by forming asexual and sexual spores. In asexual reproduction, sporangiospores are produced inside a spherical structure, the sporangium. Saporangia are supported by a large apophysate columella a top along stalk, the sporangiophore. Sporangiophores arises among distinctive, root-like rhizoids. In sexual reproduction, a dark zygosphore is produced at the point where two compatible mycelia fuse. Upon germination, a zygospore produces colonies that are genetically different from either parent.
The genus Rhizopus contains several species at least eight species, (zheng, et al 2007 and Abe, et al 2010). The most common ones Rhizopus arrhizus, Rhizopus azygosphores, Rhizopus microspores, Rhizopus schipperae and Rhizopus stolonifer. Some morphological features, such as the length of rhizoids and sporangiophores, the diameter of sporangia, the shape of columella, and the size, shape and surface texture of sporangiospores aid in the differentiation of Rhizopus species from each other. Maximum growth temperature also varies from one species to other.
Rhizopus species is a cosmopolitan filamentous fungus found in soil, decaying fruits and vegetables, and old bread, while they are common contaminants, they are also occasional causes of serious (and often fatal) infections in humans. Some species are plant pathogens. The infections may also be a complication of diabetic ketoacidosis (Chinn, 1982). Rhizopus species are among the fungi causing the group of infections referred to as Zygomycosis. Although the term mucormycosis has often been used for this angio-invasive disease. Rhizopus arrhizus is the most common cause of Zygomycosis and is followed by Rhizopus microspores var. rhizopodiformis. Zygomycosis include mucocutaneous, rhinocerebral, genitourinary, gastrointestinal, pulmonary and disseminated infections. Zygomycosis is frequently fatal.
Most Rhizopus are dependents on sugar and starch which it acquires from food matters such as bread and soft fruit. They uses the food source for growth, nutrition and reproduction (James and Donel, 2007).
Rhizopus species has the ability to quickly form on any surface in which it obtains food. It is the fastest growing, mold that is filamentous and prefers moist environment (Jeraj, et al 2005). Effect of contaminated bread in the societies can lead or cause the fungal diseases when ingested, as a result of this, a lot of consideration should be given to bread that are served in the community to be sold and this is done by the standardized system called “Hazard Analysis critical control point” (HCCP). This method is now generally considered for ensuring safety of food (Jay 1996, and De Beer and Beunier 1999). Hazard analysis critical control point involves in identifying places in the production process where hazard could occur i.e the critical control point (CCP) and put monitoring procedures in places to prevent these hazard from occurring. Even with this system in place, a sample still needs to be tested for the presences of microorganisms.
1.2 Statement of Problem
A well identified and important problem relating to the spoilage of bread cause by Rhizopus is the health hazard associated with ingestion of contaminated bread (which is zygomycosis of different type). The U.S government’s Occupational Safety and Health Administration (OSHA) classifies Rhizopus species as an allergen and irritant and a cause of hypersentive pneumonitis and dermatitis. The various ways of which the bread is contaminated and ways of isolating and identifying these fungi from bread.
These problem really propelled me to know the cause of the contamination, whether it is from the poor hygiene neither of the bread makers or because of the fungi ubiquitous nature throughout most environment.
1.3 Aim of the Study
The aim of this research was to isolate and identify Rhizopus that is associated with the spoilage of bread.
1.4 Objective of the Study
The objectives of the study were:
– To examine the growth of Rhizopus on bread at room temperature.
– To identify the various Rhizopus species that is associated with decaying bread.
– To isolate the various Rhizopus species that is associated with the spoilage of bread.
– To examine the rate of growth of the various species.
– To point out the pathogenicity of the microorganisms on human.
1.5 Scope of the Study
The scope of the study is restricted to the isolation and identification of the various Rhizopus species that is associated with decaying bread. The bread was purchased from bread sellers in Oko, Orumba North Local Government Area. Examination of the various Rhizopus species growth and identifying them.
1.6 Significance of the Study
– At the end of this research, the various bread companies will understand the cause of the spoilage of their bread.
– The consumers will benefit from this research as they will understand the health risk of consuming contaminated bread.
– The Nigerian’s at large will also benefit from the research work because the research work will bring about decrease in the rate of contamination as the bread makers have know the source of contamination and willx work on them, thereby increasing the country’s economy.
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