Antimicrobial Activity of some Egyptian Citrus Peels Extracts
Ghada M. Kholaf , Emad G.Gomaa and Hamid M. Ziena
Citrus juice production generates 15 million tons of wastes a year in the world, including peels, seeds and fruit pulps. This study aimed to evaluate the antimicrobial activity of extracted essential oils from six Egyptian citrus fruit peels. This antimicrobial activity was determined by paper disc diffusion method against six fungal strains and nine bacterial strains. Maximum inhibition zones were resulted against Penicillium sp and Aspergillus niger CAIM 147 with oils of lime and lemon peels which were extracted by hydrodistllation. In addition, the lime oil was more effective on fungal strains than lemon oil. The results showed also that oils of mandarin, sour orange and sweet orange peels extracted by the same method did not show any antifungal activity on the all tested fungi. While grapefruit peel extract has moderate effect on some fungal and bacterial growth. Also these essential oils of lime and lemon peels had very strong antibacterial activity on Bacillus subtilis DBDR 100, Clostridium botulinum ATCC 3584, Escherichia coli CCM 5172, Klebsiella pneumonia ATCC 12296 and Salmonella senftenbergy ATCC 8400. The essential oils extracted by organic solvents from all citrus fruit peels used in the present work were moderate weak activity against tested fungi and bacteria. The obtained results agreed with the phenolic contents in the essential oils extracted from citrus fruit peels and the results showed that increasing of phenolic content in these oils increased the diameter of inhibition zones of the all tested fungi and bacteria. The results showed that the lime peel oil extracted by hydrodistillation (10µl) was more effective and completely inhibited the growth of A. niger and Penicillium sp compared with lemon peel oil. Different concentrations of oil lime extracted by hydrodistllation were more effective against bacterial strains activities compared to lemon oil. B. subtilis was more sensitive at low concentration (10µL) of lime oil followed by K. pneumonia and S. senftenbergy at 30µL under the same conditions. And E. coli and Cl. botulinum were more resistant with lime oil until 50 and 40µL of lime oil, respectively. On the other hand, 20µL of lemon peel extracted by hydrodistillation completely inhibited the growth of B. subtilis, while the minimum inhibitory concentration (MIC) of oil lemon peel was 30µL for K. pneumonia and S. senftenbergy, 40µL for E. coli and 50µL for Cl. botulinum. Accordingly, the essential oils of lime and lemon peels extracted by hdrodistllation contained antimicrobial compounds which can be used as preservatives in the food industries.
Keywords: Citrus peel extract, antimicrobial activity, hydrodistillation, extraction, phenolic content.