Isolation and characterization of a mixed bacterial consortium isolated from the Juru River, Malaysia in decolourising azo dye (Reactive Red 120)
The application of microorganisms in Reactive Red 120 (RR120) remediation has gained significant attention. Textile effluents containing RR120 is known for its carcinogenicity and mutagenicity. The major issue in the biodegradation of RR120 by microorganisms is it is very difficult to isolate mic...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2021
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/112973/1/112973.pdf |
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| Summary: | The application of microorganisms in Reactive Red 120 (RR120) remediation
has gained significant attention. Textile effluents containing RR120 is known for
its carcinogenicity and mutagenicity. The major issue in the biodegradation of
RR120 by microorganisms is it is very difficult to isolate microorganisms able to
utilise the dye as a carbon source as this can completely mineralized the dye.
This study investigates and compares the role of methods and media used in
obtaining bacterial consortia capable of decolourising RR120 as the sole carbon
source, which is extremely rare to find. Three RR120-decolourising consortia
were isolated from contaminated water samples from the Juru River, Malaysia.
Only consortium JR3 was able to decolourise RR120 as a sole carbon source
compared to the rest of the consortium. Based on 16S rRNA gene sequence
analysis and biochemical test, consortium JR3 consists of Pseudomonas
aeruginosa strain MM01, Enterobacter sp. strain MM05 and Serratia
marcescens strain MM06. It was found that a mix of the bacterial consortium JR3
was able to decolourise RR120 much faster compared to single strains of MM01,
MM05 and MM06.
Initially, consortium JR3 was able to decolourise 42.5% of 50 ppm RR120 within
24 h of incubation. Using one-factor-at-time optimisation processes, the
consortium JR3 was enhanced to decolourise 88.2% of 50 ppm RR120 within 24
h. The result illustrates that yeast extract at 0.7 g/L, ammonium sulphate at 0.75
g/L, phosphate buffer with pH 8, the temperature at 35°C and RR120
concentration at 200 ppm as the optimum decolourisation conditions required by
consortium JR3. Meanwhile, based on statistical optimisation using Response
surface methodology (RSM), ammonium sulphate 0.645 g/L, pH 8.293, 200.1
ppm of RR120, temp 34.53°C results in a decolourisation rate of 93.34% at 48
h. Discriminatory statistical analysis in modelling studies illustrates that the best
primary model was the modified Gompertz model, while the secondary model
was best suited by Aiba.
The ability of consortium JR3 to decolourise RR120 under the presence of heavy
metals such as silver, arsenic, cadmium, chromium, copper, mercury, lead, and
zinc were also investigated in this study. It was found that chromium had the
least effect on RR120 decolourisation followed by zinc and lead. Meanwhile, 1
ppm mercury has the highest inhibitory effect on consortium JR3, therefore,
reducing decolourisation of 200 ppm RR120 by 32.5%. The consortium was able
to tolerate up to 10 ppm of chromium and 1 ppm of mercury. The decolourised
RR120 product showed less inhibition effect on Vigna radiata’s seed germination
compared to the parent compound, suggesting that RR120 toxicity has been
reduced. RR120 at the lowest concentration of 25 ppm reduced seed
germination by 17.7%, shoot length by 1.13 cm and root length by 1.43 cm. The
decolourised product of 25 ppm RR120 illustrated no significant difference
(p>0.05) to control.
In conclusion, the consortium JR3 has the potential to be used in the
management of RR120 contamination in the environment. Consortium JR3 was
not only able to decolourise at high concentrations of 500 ppm RR120, but the
end product is safer compared to the parent compound alone in Vigna radiata
toxicity studies |
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