ISOLATION AND IDENTIFICATION OF BACTERIA AND FUNGI ASSOCIATED WITH THE SPOILAGE OF ORANGE

ABSTRACT

Spoilage of Citrus sinensis is the change in the organoleptic properties of the fruit belonging to the genus Citrus and the species sinensis. The aim of this work was to isolate and identify the bacterial and fungal microorganisms associated with the spoilage of oranges (Citrus sinensis).This was carried out using methods such as characterization of bacterial isolates using gram stain techniques, biochemical tests and morphological characteristics. The fungal isolates were characterized and identified employing microscope aided techniques and morphological analysis. To isolate the organisms, homogenized samples of spoilt Citrus sinensis were serially diluted on sterile nutrient agar and potato dextrose agar plates and incubated for 24 hrs for bacterial isolation and 72 hrs for fungal growth at room temperature. The samples of Citrus sinensis tested showed a massive infection with bacteria of the genera Bacillus (Bacillus cereus and B. subtilis). Escherichia coli was also isolated along with other bacteria which were Serratia species, Pseudomonas species and Staphylococcus aureus. Including fungi such as Penicillium chrysogenum, Aspergillus niger, Phoma species, Pestalotia species, Lasidopodia species and Mucor species. Pathogenicity testing showed that some of the fungal isolates were highly pathogenic and included Lasiodiplodia species and Phoma species. The results showed that spoilage of Citrus sinensis is due to bacterial and fungal microorganisms which are highly pathogenic.