Microbial decolorization of triazo dye, direct blue 71 by mixed bacterial culture isolated from Malaysian soil
Polluted wastewater from textile dyeing industrial sectors has causes severe effect towards human, plant and marine creatures and the treatment process is truly challenging. In this study, a mixed bacterial culture was isolated from Malaysian soil, screened and identified to successfully decol...
Saved in:
| Main Author: | |
|---|---|
| Format: | Thesis |
| Language: | English |
| Published: |
2020
|
| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/98596/1/FP%202021%2056%20UPMIR.pdf |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | Polluted wastewater from textile dyeing industrial sectors has causes severe
effect towards human, plant and marine creatures and the treatment process is
truly challenging. In this study, a mixed bacterial culture was isolated from
Malaysian soil, screened and identified to successfully decolorize Triazo-bond
Direct Blue 71 dye and act as the sole source of carbon and nitrogen. The free
cells were also immobilized for better decolorization at higher concentration of
dye by using sodium alginate. Response surface methodology (RSM) and
Artificial Neural Network (ANN) were used to optimize the decolorization
efficiency for both free and immobilized cells. Significant effect on DB71 dye
decolorization percentage by free cells is denoted by the experimental
variables of dye concentration, yeast extract, and pH. The optimum conditions
for dye decolorization by immobilized mixed culture were determined by four
variables which were dye concentration, alginate concentration, number of
beads and beads size. GCMS and FTIR analysis were used to characterize the
metabolites after the decolorization. Other than that, kinetics modelling study
of DB71 dye decolorization allowed the estimation of decolorization rate of free
and immobilized cells. Major bacterial group found from the metagenomics
analysis consist of Acinetobacter (30%), Comamonas (11%), Aeromonadaceae
(10%), Pseudomonas (10%), Flavobacterium (8%), Porphyromonadaceae
(6%), and Enterobacteriaceae (4%). Proteobacteria (78.61%), then
Bacteroidetes (14.48%) and Firmicutes (3.08%) were among the richest
phylum in the mixed bacterial culture. The optimum condition for free cells
predicted by RSM is at 150 mg/L of dye concentration, 3 g/L of yeast extract
and pH of 6.645. ANN predicted the optimum condition at 150 mg/L, 2.9 g/L of
yeast extract and pH of 6.7. Higher prediction and accuracy in the fitness was
found in ANN model as proved by R2
and AAD values of 0.99 and 0.04
subsequently fitness compared to the RSM. ANN model for immobilized cells
offered a better prediction than RSM with R2
of 0.99. The ANN model predict the decolorization by immobilized cell is optimum at 200 mg/L, 0.966 % of
alginate concentration, 50 number of beads and 0.599 cm of beads size.
Moreover, the result from GCMS and FTIR analysis of the metabolites from the
decolorization of dye shows that the reduction of dye caused the absence of
the untreated sample and emergence of new peaks in the treated sample in
FTIR spectrum. In addition, GCMS result from the treated sample shows no
toxic secondary metabolites were formed.
Luong model predicted the rate of decolorization by free cell at 10 %hr-1 by
using the kinetic modelling and dye concentration at 159.5 mg/L completely
inhibited the decolorization based on the Sm value. Aiba model predicted the
rate of decolorization by immobilized cell is at 4.645 %hr-1. The use of mixed
bacterial culture was found to be efficient for the decolorization of DB71 dye in
this study. The optimization of immobilized cell by using RSM and ANN using
sodium alginate resulted to better decolorization of dye at higher concentration
which is up to 200 mg/L. Moreover, the effect of metal ions towards the
decolorization shows that gel beads through immobilization were able to
protect against toxic substance. It is reflected by a great tolerance result
towards metal ions over free cells during DB71 dye decolorization where
occurrence of metal ions may disrupt the decolorization process. The
decolorization of Direct Blue 71 dye by immobilized cell was still higher than 90
% even with the presence of 1 mg/L of mercury, nickel, copper, lead, arsenic,
chromium, cadmium and silver in the solution and slight decrease of
decolorization was observed for both free and immobilized cell compared to the
control samples. In conclusion, all the objectives of this study were achieved
accordingly.
Environmental pollution caused by the released of industrial effluent containing
dye has been affecting the water quality in Malaysia. Biological practice using
microorganisms provides a complete degradation with no secondary pollutant
besides the cost effective advantage compared to the physical and chemical
wastewater treatment. There are few reported works on azo dye decolorization
by mixed bacterial culture without the aid of carbon and nitrogen source.
Therefore, this study found and optimized a potent mixed bacterial culture that
could degrade Direct Blue 71 dye in facultative anaerobic condition and no
added carbon and nitrogen sources are needed to completely decolorize the
dye with no introduction of secondary toxic metabolites based on the
metabolites analysis result. |
|---|