A study of probiotic potentials of lactic acid bacteria isolated from fermenting cassava

Orike, Emmanuel Lucky (2015)

xvii,121

Thesis

This study was undertaken to isolate, identify lactic acid bacteria (LAB) from fermenting cassava and investigate their probiotic properties with a view to selecting the best strain(s) that could be useful in the probiotication of pasteurized orange juice. Matured cassava tubers were obtained from the ObafemiAwolowo University Teaching and Research Farm Ile Ife, Nigeria. The cassava tubers were peeled, cut into small sizes, washed, soaked in clean tap water and left to ferment at room temperature for up to 96 h. Aliquot (5 mL) of the soak water was aseptically obtained for isolation of LAB following standard methods. The probiotic properties such as acid and bile salt tolerance, antagonistic activities against selected pathogens, hemolytic activity and exopolysaccharide production of the isolated LAB were studied. The best LAB strain(s) were selected based on their probiotic properties for probiotication of orange juice. Fresh ripe oranges were squeezed, the juice extracted and pasteurized at 95oC for 30 seconds. The juice were inoculated (108 cell/mL orange juice) with the selected LAB strains singly and in combination and stored at room temperature (30 ± 2oC) and 4oC for 20 days. During storage, samples were obtained at 5 days interval for pH, titratable acidity and viable counts. Twenty-four strains of LAB were isolated from fermenting cassava which showed varied tolerance to various acidic pH levels and bile salt concentrations. The isolates did not display hemolytic activity which was indicative that they were non-pathogenic. Twenty-three of the LAB strains showed antagonistic activity due to the production of organic acids against Staphylococcus aureus and E. coli NCIB 86. About 83.3% of the LAB strains produced exopolysaccharide.Of the 24 strains,Lactobacillus plantarum (A2) and Lactobacillus delbrueckii (C2) were selected based on their technological properties as possible probiotic strains for probiotication of pasteurized orange juice. The viability of the selected probiotic LAB in the pasteurized orange juice were within the recommended population (106- 108 cfu /mL) after 20 days of storage at 4oC while it dropped to 105at room temperature storage. The organoleptic evaluation showed that the probiotic orange juice inoculated with L. delbrueckii (C2)and the mixed culture of the probiotic strains were not significantly different from the uninoculated pasteurized orange juice in all the organoleptic attributes (taste, aroma, appearance and general acceptability) scored by the taste panelists, an indication that L. delbrueckii(C2) played an important role in contributing to the development of these sensory attributes. The study concluded thatL. plantarumand L. delbrueckii might be useful as probiotic culture for the production of healthy functional drinks which might solve the problem associated with probiotic dairy products especially for lactose intolerant people.

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