Decolorization of metanil yellow dye by free and immobilized bacterial cells
Textile industry is one of the leading industries that contribute to economy. The oldest man-made chemicals and are widely used in the textile industries are a type of azo dyes. Globally, 2.8×105 tonnes of textile dyes are poured into water ecosystem every year. This has several adverse effects o...
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Format: | Thesis |
Language: | English |
Published: |
2021
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Subjects: | |
Online Access: | http://psasir.upm.edu.my/id/eprint/104549/1/FP%202022%203%20IR.pdf |
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Summary: | Textile industry is one of the leading industries that contribute to economy. The
oldest man-made chemicals and are widely used in the textile industries are a
type of azo dyes. Globally, 2.8×105 tonnes of textile dyes are poured into water
ecosystem every year. This has several adverse effects on life including
decreased aquatic photosynthesis, ability to exhaust dissolved oxygen and toxic
effect on flora, fauna and also humans. The presence of dyes in the textile
effluent also causes an unpleasant appearance by imparting the color and also
their breakdown products (colorless amines) which are toxic, carcinogenic and
mutagenic. One of the examples of azo dyes is Metanil Yellow (MY) dye. MY is
a type of azo dyes that is toxic to humans and also environment. Thus, this study
is conducted with aims to overcome these problems. For the first objective, which
is to isolate, screen and identify MY dye decolorizer from mixed culture and
optimization of MY dye decolorization using RSM. The mixed bacterial culture,
FN3 was isolated from agriculture soil in palm estate in Universiti Putra Malaysia,
(2.9876,101.7234). Forty samples were screened for dye decolorization. The
screening process was performed using different dye concentration ranging from
100 mg/L to 400 mg/L. The mixed culture was prepared by dissolving 5.0 mL of
the soil suspension (10% v/v) in 50.0 mL of minimal salt medium (MSM)
supplemented with desired concentration of MY dye in 250 mL conical flask. The
conical flask was incubated at room temperature on a rotary shaker at 120 rpm
for 24 hours. The cultures were maintained by subculturing into new MSM media
every 3 days and were kept in 8°C. It was later determined that isolate FN3 able
to decolorize MY up to 90% of MY dye in 24 hours. Mixed bacterial culture FN3
was then identified using metagenomics analysis. This analysis determined that
the mixed bacterial culture FN3 comprised of Bacillus sp with percentage of up
to 42.6%. The second highest of bacteria found in the mixed culture was from
genus Acinetobacter with percentage of 14%. Fungi diversity analysis was also
performed using Internal Transcribed Sequence (ITS). It was determined that
97% of mixed culture FN3 was “unclassified” fungi and 3% consisted of Candida sp. After that, the optimization of MY decolorization was performed using the
methodological approach of Response Surface Methodology (RSM). From the
optimization, it was determined that the optimum conditions were 72 mg/L of
Metanil Yellow dye concentration, 1.934% of glucose concentration, 0.433 g/L of
ammonium sulphate and pH of 7.097. The analysis of variance (ANOVA)
demonstrated that the model was significant based on the low probability value
(F<0.0001). The goodness of fit of the model was checked using the
determination coefficient R2. The value of R2 was 0.9125 that indicated good
relation between experimental and predicted values of response. The nonsignificant
value of lack of fit (>0.05) shown that the quadratic model was
statistically significant for the response and thus can be used for further analysis.
Next, for the second objective which is to optimize the MY dye decolorization of
immobilized mixed culture FN3 using RSM and to study the effects of heavy
metals ions towards MY dye decolorization. The mixed bacterial culture of FN3
was immobilized using gellan gum and optimized using the same approach,
RSM for optimum dye decolorization. It was determined that the optimum
conditions were as follows; 130 mg/L of dye concentration, 1.478% of gellan gum
concentration, 50 beads and 0.6 cm of beads size. The ANOVA test
demonstrated that the model was significant for dye decolorization (F<0.0001).
The value of R2 was 0.9767 which is close to 1 indicating that the correlation
between the predicted and experimental values are good. The lack of fit for the
model was 5.8 and statistically insignificant implying that the model was
statistically significant for the response and can be used for further analysis. The
reusability of the microbials beads in dye decolorizing was tested. It is
documented that the immobilized beads was able to be reused up to 15 times
without substantial loss of catalytic activity. The effects of metals ions were also
tested to the free cells and immobilized beads of mixed bacterial culture FN3. It
was shown that dye decolorization of MY by the mixed bacterial culture was not
affected by the presence of 1 mg/L of the metals ions of argentum, lead, cobalt,
copper, zinc, cadmium, chromium, arsenic, nickel and mercury. The ability of the
immobilized beads has made this as a great potential of bioremediation tools. |
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