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Addis Ababa University Libraries Electronic Thesis and Dissertations: AAU-ETD! >
Faculty of Medicine >
Thesis - Anaesthesiology >
Please use this identifier to cite or link to this item:
http://hdl.handle.net/123456789/107
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| Title: | ANTIMICROBIAL ACTIVITY OF LACTIC ACID BACTERIA ISOLATED FROM ‘ERGO’, ETHIOPIAN TRADITIONAL FERMENTED MILK, ON SOME FOODBORNE PATHOGENS |
| Authors: | Esayas, Assefa |
| Keywords: | Lactic acid bacteria
Inhibition
Fermented milk
Ergo
E.coli
S. typhi
S |
| Date Added: | 7-Sep-2007 |
| Abstract: | “Ergo” is a traditional Ethiopian fermented milk produced by spontaneous fermentation
using traditional utensils under non-hygienic environment. To produce microbiologically
safe and chemically defined product; study on the production, processing, utilization and
handling of ‘Ergo’ under different agro-ecological zones as well as the isolation and
characterization of potential lactic acid bacteria strains with the potential production of
inhibitory factor should be the first essential step. In this study ninety-smallholder
farmers from the three districts (Lumme, Fentale, Adami Tulu), thirty from each district,
who produced and processed milk were purposeively selected and individually
interviewed using a semi-structured questionnaire to asses the production, processing,
utilization and handling of traditional fermented milk, “Ergo”. Milk fermentation takes
relatively longer period (3.57 + 1.04 days) in Lumme district than the two districts
Fentale and Adami Tulu (1.03+ 0.183). All households (100%) in Fentale consume unboiled
milk; rather they utilize it in its fermented or raw state, where as only 40% and
46.6% of households in Lumme and Adami Tulu areas, respectively, used fermented milk
for consumption. Even though milk is fermented and consumed in all these areas a very
limited hygienic care is practiced, 93.4% of the households do not heed for the sanitary
aspect of the milk and milk products. To evaluate the antimicrobial activity of the lactic
acid bacteria (LAB), 112 strains of LAB, belonging to Lactococcus, Lactobacillus,
Entorococcus, Streptococcus, Leuconostoc and Pediococcus were isolated from
Ethiopian traditional fermented milk, “Ergo”. Moreover the culture filtrates of all the
isolates were examined for antimicrobial activity on some food born pathogens
Salmonella thyphi, Shigella flexineri , Staphylococcus aures (ATCC-25923) and
x
Escherchia coli (ATCC-25922) using disc diffusion assay method. Inhibition diameters
obtained with the inhibitory substance of 2mm and above inhibition zone over the control
were considered as positive. Twelve strains of lactic acid bacteria that produced the
greatest antimicrobial substance were selected. These strains were identified as species
of Lactobacillus acidophilus(2) , Lactobacillus plantarum(2), Lactococcus lactic spp
crimoris(2) , Lactococcus lactic spp lactic(3), Leuconostoc lactic (1) , Pediococcus
pentosaceus(1) and Pediococcus sp.(1). All the inhibitory substance-producing strains
were tested for their temperature and pH stability. The antimicrobial activity of the
culture filtrate of isolated strains were completely inactivated when treated at 121oC for
15 minutes, where as at 30, 60 and 80oC there were no Significant (P>0.05) difference in
diameter of inhibition compared to untreated (control). The entire culture filtrate were
stable with in a wide range of pH (2-10) and no significant (P>0.05) difference was
observed between the treated filtrate and the untreated (control). However treating the
culture filtrate at pH 12 has significantly (P<0.05) decreased the inhibition diameter. |
| Description: | A Thesis presented to the School of Graduate Studies of the Addis Ababa University in
partial fulfillment of the Degree of Master of Science in Biology (Applied Microbiology) |
| URI: | http://hdl.handle.net/123456789/107 |
| Appears in: | Thesis - Environmental Sciences
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