Antimicrobial Activities of Citrus aurantiifolia Peels on Microorganisms Isolated from Spoilt Onions Sold in Awka, Anambra State, Nigeria

Abstract

One of the most significant monocotyledon crops is the onion, which also contains antioxidants. This research aims to isolate microorganisms that cause spoilage in onion and to study the anti-microbial activities of lime peel extract on the isolates. Spoilt Onion samples were collected from three different markets in Awka Metropolis (Eke Awka, Nnamdi Azikiwe temporary site (Temp. site) and Amenyi). They were then transported to Alpha research laboratory Awka, for analysis. The spoilt onions samples were sterilized and cultured using the standard procedure. The culture media used for the study were Nutrient Agar and Sabroud Dextrose Agar, both were placed into a conical flask and subjected to an autoclave at a rate of 121ºC at 15psi for 20 minutes and the plates were incubated at room temperature. In the study, various microorganisms that can caused spoilage were identified; the bacteria include Klebsiella sp, E-coli, Staphylococcus spp and pseudomonas spp.  The fungal isolates are Aspergillus sp, Penicillium sp, Mucor sp, Rhizopus sp. They were isolated and identified both morphologically and microscopically. Samples from Amenyi had the highest fungal counts (4.50 × 10⁴ ± 0.00a cfu/g) while samples from Eke-Awka had the lowest fungal count (2.70 × 10⁴ ± 0.200c cfu/g) on SDA. Also, samples from the Temp. site had the lowest bacterial counts (4.71 x 10⁴ ± 0.100c cfu/mi) while samples from Eke-Awka had the highest fungal count (6.10 x 10⁴ ± 0.03a cfu/ml).  The result showed that ethanol extract from lime peel has good inhibitory effects of the organisms. Rhizopus sp. had the highest inhibition at 100% of lime peel extract while Aspergillus sp. has no inhibition at 100%, 50%, and 25% of lime peel extract. Also, Escherichia coli had the highest inhibition of (43.00 ± 0.30) at 100% of lime peel extract while Pseudomonas had no inhibition at 100%, 50%, and 25% of lime peel extract. As a result, the study recommended that farmers utilize lime peel extract, which is a much safer and more effective technique of controlling onion spoilage.