IDENTIFICATION AND CHARACTERISTICS OFÂ MICROBES ASSOCIATED WITH MARKET DISEASES OF PAWPAW FRUITS ( CARICA PAPAYA) IN UYO METROPOLIS
DEPARTMENT: MICROBIOLOGY
ABSTRACT
The study was carried out to isolate, characterize and identify microorganisms associated with market diseases (rots) of paw-paw fruits from markets around Uyo metropolis. Also to determine the pathogenicity of the isolates. Isolation of bacteria was carried out using Nutrient agar and MacConkey agar while the fungi isolation was done using Sabouraud Dextrose agar. Five genera of bacteria: E. coli, Salmonella sp, Clostridium sp, Pseudomonas sp and Staphylococcus aureus and three of fungi: Aspergillus sp, Rhizopus sp and Mucor sp were Isolated from these samples. Paw-paw fruits from Akpan Andem market recorded the highest number of both bacteria and fungi, while those from Afaha market had the least microbial load. Staphylococcus aureus and Salmonella sp had the highest percentage occurrence (31.25%). Rhizopus sp had the highest percentage occurrence for the fungi (43.75%). Pathogenicity test revealed that of all the isolated fungi, Rhizopus sp(3.4cm) was most virulent, causing rots in fresh pawpaw within 3-5 days while Aspergillus sp(0.6cm) was the least virulent. While Salmonella sp (2.6cm)was most virulent for the bacteria isolate causing rot within 5days with E .coli causing the least rot(1.0cm)Â Since most of the organisms isolated from the paw-paw fruits are also human pathogen, there are hazards associated with the consumption of these fruits. It is therefore recommended that fruits obtained from the open markets should be well washed before being eaten.
CHAPTER ONE
1.00 BACKGROUND OF STUDY
Carica papaya commonly known as pawpaw, a poor man’s banana is a member of the small family Caricaceae allied to the Passifloraceae . This family comprises of Jamilla, Jacarta, Cycliomorpha and Carica genera (Oluma,1992) . The only species cultivated for their fruits is carica. Pawpaw is thought to originate from the lowlands of Eastern central America, from Mexico to Panama (Nakasone,1998).Its seeds were distributed to the Carribean and South east Asia during Spanish exploration in the 16th century from where it spread rapidly to India , the Pacific and Africa (Villegas,1997),pawpaw is now grown in all tropical regions of the world .It is one the tropical plant grown all over West Africa mainly for local consumption. It also grows as a semi-wild plant from discarded seeds (Kuthe and Spoerhase, 1974)
It is a soft-wooded perennial plant that lives for about 5 -10 years (Chay-Prove, 2000). Pawpaw is a fast growing but short lived herbaceous plant with latex vessels in all its plant parts. It has an upright branched or un-branched stem covered all over with leaf scars (Agnew,1968).These  fruits are ready to harvest five to six months after flowering, which occurs five to eight months after seed germination (Chay- prove,2000). The fruit range in size from 7-30cm long and vary in mass from about 250-300g (OECD,2003).
Fruits are consumed raw in order to obtain their valuable nutrient in the best form, fruits are good source of nutrients for growth, repair and control of body processes as it contain sugar, vitamins, mineral element, carbohydrate, proteins, ash, and oil in small quantity (Duckworth, 1997).Man has utilize pawpaw fruit in the production of Jams, Marmalads and in wine production (Hobbs, 1998). Apart from their usage as a source of food, the fruits, seeds, leaves and latex of pawpaw are used medicinally (Beckstrom-Sternberg, 1994). Pawpaw fruit is used as a digestive agent and it is also used to clot blood after surgery due to the presence of an enzyme papain.
Nutritionally, pawpaw is a good source of calcium, and an excellent source of vitamins A and C (Ayers et al, 1980). Biochemically, its leaves and fruits are complex containing several proteins and alkaloids with important pharmaceutical and industrial applications (El Moussaoui,2003). Papain is associated with protecting the plant from herbivorous and frugivorous predators. The papain is also used in tendering meat, in degumming silk and for softening wool (Villegas, 1997). Consumption of papaya may cut the risk of certain cancer, various isothiocyanates are effective anti-cancer agent and pawpaw contains benzyl isothiocyanates (Nakamura, 2009).
Due to the high nutritional value, particularly sugar and low pH, fruits serve as a breeding substrate for micro organisms whose activities constitute the most important causes of spoilage. Microbes from many sources such as agricultural environment. vegetative and market environment also contaminate fruits. Michael et al (1958) and Duckworth (1966) reported that tree borne fruits like pawpaw are contaminated more readily with spores from the infections on surrounding vegetation.
Since the fruit s are harvested locally, there are always bruises and cuts due to the basket used in transporting the fruits(Adisa,1983).The fruits are displayed on benches and in basket in the markets until they are sold, thereby exposing them to further microbial infection (Baiyewu and Amusa,1999).
Market diseases are rots that become obvious on the fruits while they are in the market, the rots might be caused by microbes that got on the fruits during harvest, transportation or in the market. Gupta and Pathak (1986) reported that Aspergillus niger, Aspergillus flavus Rhizopus oryzae, Fusarium equiseti, and Fusarium moniliforme are some fungi that affect pawpaw ,(Anons,1975) has also reported that pathogenic bacteria normally found in the fruits include Salmonella sp, Staphylococcus sp, Bacillus sp  and these microbes causes various diseases like Salmonellosis, typhoid, gastroenteritidis, aflatoxins, anthracnose, powdery mildew, blackspot, root-rot and rotting fruits.
According to (Krogh,1992), most of the fruits displayed in the market has cuts and bruises which aids penetration of microbes and these fruits are mostly preferred by low income earners because they are relatively cheap. Besides the losses in income to fruits marketers, consumption of spoilt fruits causes serious health hazards. (Prasad,1992) the ability of an organism to survive or endure a given low or extreme conditions of environmental factors, but its ability to carry out its complete life cycle(Jay,2005).
(Jay,2005) wrote that some parameters are inherent in the tissues of plant  which aids the multiplication of microbial activities, these parameters include pH , moisture content, oxidation-reduction potential, nutrient content etc. Fruits generally have low pH thereby aiding the growth of moulds and yeasts while bacteria grows around neutral pH that is 6.6 to 7.5. Microbes utilize sugar, amino acids, vitamins present in fruits for their growth and multiplication.
1.01 LIMITATIONS
Pawpaw is highly perishable due to it juicy and fleshy nature, mention is also made of skin irritation in pawpaw harvesters, and excessive consumption of pawpaw causes carotenemia (yellowing of soles of feet and palms. (FAO,2004)
 1.02 AIMS AND OBJECTIVES
To isolate, identify and characterize the microbes associated with market diseases of pawpaw fruits. To determine the pathogenicity of the isolates
