Isolation and Evaluation of Azo Dye Decolorizing Microorganisms from Ethiopian Alkaline Soda Lakes
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Date
2008-07-04
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Addis Ababa University
Abstract
Textile dye decolorizing microorganisms were isolated from Ethiopian alkaliphilic Soda lakes. A total of 121 morphological distnict colonies were isolated from mineral salts medium-agar plate. When these isolates were subjected to confirmed decolorizer and non-decolorizer using mineral salts media containing 10 mg/l of Reactive Red 184, 95 isolates were found to be decolorizer while the rest were non-decolorizer. By selecting 25 isolates decolorizing the dye rapidly, further screening were carried out using 25 mg/l of Reactive Red 184. Among the 25 isolates, 8 isolates which decolorized the dye > 80% in the first 24 h were selected and subjected to further screening using various concentration(50-150 mg/l) of Reactive Red 184. A55 which decolorized > 82 % of the tested dye concentration in one day was selected as an efficient isolate for further studies. The effect of nutrient composition (carbon and nitrogen), culturing condition (anaerobic, anoxic, shaker, and aerobic), dye concentration and dye type on decolorization of Reactive red 184 was evaluated using isolate A55. Maximum extent of decolorization at the end of the fourth day was observed when carbon (98-100%) and organic nitrogen (100%) sources were used in the medium. The presence of sodium nitrate inhibited decolorization activity ranging from 1-29 % through four consecutive days of incubation. Decolorization was efficient (100%) in anaerobic and anoxic cultures. However, A55 showed good growth in aerobic and agitated culture, color removal was strongly inhibited. The decolorizing activity was found to decrease with increasing dye concentration from 50 - 250 mg/l in the first day, but at the end of the fourth day almost equal percentage of decolorization was observed. The isolate was found to decolorize a total of seven dyes ranging from 51-100 % at the fourth day of incubation.
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Keywords
Alkaliphilic, Decolorization, Decolorizing Microorganism, Reactive Red 184 Textile Dye