The in vitro antilisterial activities and time kill regimes of crude aqueous and n-hexane extracts of the husk fiber of Cocos nucifera were assessed. The aqueous extracts were active against 29 of the 37 test Listeria isolates while the n-hexane extracts were active against 30. The minimum inhibitory concentrations (MICs) of all the susceptible bacteria ranged between 0.6 and 2.5 mg/ml for the aqueous fraction and between 0.6 and 5.0 mg/ml for the n-hexane extract. The average log reduction in viable cell count in the time kill assay ranged between 0.32 Log 10 and 3.2 Log 10 cfu/ml after 4 h of interaction, and between 2.6 Log 10 and 4.8 Log 10 cfu/ml after 8 h interaction in 1 × MIC and 2 × MIC (aqueous extract); and between 2.8 Log 10 and 4.8 Log 10 cfu/ml after 4 h of interaction, and 3.5 Log 10 to 6.2 Log 10 cfu/ml after 8 h interaction in 1 × MIC and 2 × MIC for the n-hexane extract. The extract was bactericidal against one of the test bacteria at 1 × MIC and against three of the test bacteria at 2 × MIC for the 8 h interaction period for the aqueous extract, while for the n-Hexane fraction; the extract was bactericidal against all the five test bacteria at both MICs after the 8 h interaction period. We suggested that the crude aqueous and n-hexane extracts of the husk of C. nucifera could be bacteriostatic or bactericidal depending on the time of exposure and concentration.
Corynebacterium sp was isolated from the soil by using 3-5 dinitro benzoic acid (DNB) as a sole carbon source. The highest rate of degradation of aniline (AN) or DNB was found in the exponential phase of the growth of the bacterium. After 24 h, about 50% of DNB and 30% of AN were degraded by Corynebacterium sp. At a concentration of 0.5 to 1 g/L of AN or DNB, good growth was obtained and the protocatechuic acid was detected. The optimum concentration of yeast extract was 2 g/l. Catechol 1-2 dioxygenase was induced in the cells grown on a medium containing AN or DNB. A significant activity of this enzyme was detected, which means that ortho cleavage pathway may be present in Corynebacterium sp.
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