Isolation and screening of synthetic dye degrading bacteria from textile effluents in Western Province, Sri Lanka

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2024

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Faculty of Science, University of Kelaniya Sri Lanka

Abstract

Synthetic dyes in the textile industry contribute significantly to environmental pollution, particularly through effluents. Numerous chemical and physical methods have been developed during the past few decades to eliminate toxic dyes from wastewater. Most of these techniques have limitations, such as the generation of sludge and additional negative environmental and economic effects caused by increased chemical demand. This study aimed to isolate and characterise the bacterial strains from textile effluents with the ability to degrade synthetic dyes, which could serve as a solid basis for establishing viable bioremediation techniques. The focus was directed on efficiently recycling wastewater containing textile dye effluents. The effluent samples were collected from industrial discharge points in Negombo and Biyagama, and the bacterial strains were isolated using a modified nutrient agar medium containing dye. The isolated strains were characterised by observing their morphological and biochemical characteristics, which included gram staining, catalase test, and the triple sugar iron test. An initial test for dye degradation was carried out using two synthetic dyes, Acid red 88 and Methylene blue, at 37 ˚C for 72 hours. The degradation efficiency was quantitatively measured using a UV-visible spectrophotometer in a dye decolourization assay. The bacterial isolates with higher efficiency in dye degradation were further tested for the effect of environmental changes, such as pH and dye concentration variations. The isolates were tested in duplicates for their growth and decolourising ability in a dye-containing media at pH 5 and pH 9 and at 5 mg/l and 20 mg/l dye concentrations. Most of the selected isolates showed decolourisation of 53-66% at pH 5 and 65-94% at pH 9 for acid red 88 within 48 hours. Among the selected isolates, acid red 88 containing media, L2(06) achieved the highest decolourisation of 93.93 ± 0.92 % after 48 hours of incubation at pH 9 (p=0.0001). Several isolates decolourised methylene blue 68-83% at pH 5. Isolate L2(07) was identified to decolourise in methylene blue in both pH levels, achieving decolourisation of 82.28 ± 7.56 % in pH 5 (p=0.02) and 92.33 ± 1.48 % in pH 9 (p=0.01). Moreover, most isolates showed decolourisation above 95% at 5 mg/l and 84% at 20 mg/l in acid red 88 media. For methylene blue, all selected isolates showed decolourisation above 70% in both concentrations. The results revealed the successful isolation of several bacterial strains capable of degrading two different acid red 88 and methylene blue concentrations within a pH range of 5-9, suggesting their adaptability to diverse industrial effluent settings. This research contributes important new understandings of the microbial ecology of synthetic dye degradation in textile effluents and lays the groundwork for creating environmentally friendly and long-lasting bioremediation techniques.

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Keywords

Acid red 88, Biodegradation, Decolourisation, Methylene blue, Textile effluents

Citation

Fernando W. P. E. M.; Wijesinghe L. H.; Wickramasinghe P. M. T. B.; Senarath G. L. C. N. T.; Efrem S. M. (2024), Isolation and screening of synthetic dye degrading bacteria from textile effluents in Western Province, Sri Lanka, Proceedings of the International Conference on Applied and Pure Sciences (ICAPS 2024-Kelaniya) Volume 4, Faculty of Science, University of Kelaniya Sri Lanka. Page 163

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