IN-VITRO STUDIES ON NANOPARTICLE MEDIATED BIODEGRADATION OF ELECTRONIC WASTE BY NATIVE BACTERIA
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Date
2023-02-01
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Abstract
The management of electronic waste (e-waste) becomes a global issue in this
digital era. Plastics are neither the main residue nor the most important pollutant in
electronic trash, but they take up a lot of room due to their low density and the forms of
their parts. They make up about 17 percent of the WEEE (Waste from Electrical and
Electronic Equipment) stream. More than 55% of all the polymers in e-waste are made up
of ABS (Acrylonitrile Butadiene Styrene) and HIPS (High Impact Polystyrene Sheet).
Existing conventional practices are harmful for dealing with e-waste, therefore, indigenous
soil bacteria were explored for e-waste treatment through enrichment culture approach
followed by screening, identification and their characterization used for in-vitro
biodegradation investigation. Soil bacteria were enriched in the presence of e-waste for 6
months and the findings were established through optical density value that were higher in
the case of soil enrichment than the control. Based on their morphological, biochemical and
molecular characterizations, the bacterial isolates MGP1, MGP4 and MGP15 were
identified as Bacillus aryabhattai, Sporosarcina sp., Rhodococcus kroppenstedtii. The
selection and biocompatibility testing of potential isolates were performed for the
formation of bacterial consortia. All the isolates displayed their best performance at pH 7,
temperature 30°C and shaking speed 120 rpm. Supplementing the nutrient medium with
additional carbon and nitrogen sources enhanced the rate of polymer degradation by the
bacterial isolates. A known bacterial strain Pseudomonas fluorescens was selected for the
degradation of the electronic waste and its comparison with that of screened bacterial
isolates. Comparative studies showed that e-waste degradation potential of consortium is
better than the individual bacterial strains. Titanium Dioxide (TiO2) nanoparticles were
used to study its effect on biodegradation ability of the best suited bacterial strain.
The biodegradation of e-waste by the selected strains during in vitro experiment
was confirmed by analytical processes like FT-IR, FESEM, EDX elemental analysis. Thus,
this study besides providing direct and standardized protocol for screening and selection of
efficient e-waste utilizing bacteria is also demonstrating potential consortia which are ready
to be used. The bacterial isolates were able to degrade e-polymer both in media and soil
and therefore can be used profitably for field scale bioremediation technology.
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Theses of Ph.D