Biomineralization of PET (Polyethylene terephthalate) plastic through Sporosarcina species for plastic waste management

Abstract

Purpose: This research work was done as an essential assignment to complete my thesis. It was aimed at finding an indigenous Sporosarcina. species that can produce calcium carbonate precipitates both in absence and presence of PET flakes through ureolysis. So that this strain in future can be used in treating PET flakes that make these flakes compatible with cement concrete (when added in concrete) and decrease the gaps between the PET flakes and cement matrix. Materials and Methods: Three Sporosarcina closely related species bacteria strains (NCCP- 2331, NCCP-2222 and NCCP-2716) and one already reported of producing calcium carbonate precipitates through ureolysis Bacillus subtilus were provided by National culture collection of Pakistan. The experiment that was designed included mixing of these strains overnight grown culture, CPM (Calcium carbonate precipitation media) that included ammonium chloride, sodium bicarbonate, calcium chloride and urea and in one case 1g PET flakes were added while in other case no flakes. Negative control was also run along the experiment in that flask there was not any bacteria colony inoculated. Then the precipitates were analyzed by XRD, FTIR and SEM to confirm their structure. Results: All three strains had shown ureolytic activity and had produced calcium carbonate precipitates both in the absence and presence of PET flakes. Among these three strains NCCP- 2331 had shown the more capability to produce calcium carbonate precipitates and its precipitates were more crystalline while NCCP-2716 and NCCP-2222 precipitates were more amorphous. XRD, FTIR and SEM analysis confirmed the structure of calcium carbonate crystals. SEM analysis also confirmed the formation of biofilm and calcium carbonate layer over the PET flakes. Conclusion: Among three strains NCCP-2331 had shown the best capability to produce calcium carbonate precipitates when it was provided calcium carbonate precipitation media. That indigenous strain can be used in future for biotreatment of plastic flakes while adding these flakes in cement matrix.