Harshita Negi

Biodeterioration studies of thermoplastics in nature using indigenous bacterial consortium

Thermoplastics, poly vinyl chloride and low-density polyethylene were treated in the presence of indigenously developed bacterial consortium in laboratory and natural conditions. The consortium was developed using four bacteria, selected on the basis of utilization of PVC as primary carbon source, namely P. otitidis, B. aerius, B. cereus and A. pedis isolated from the plastic waste disposal sites in Northern India. The comparative in-vitro treatment studies as revealed by the spectral and thermal data, illustrated the relatively better biodegradation potential of developed consortium for PVC than the LDPE. Further, the progressive treatments of both the thermoplastics were conducted for three months under natural conditions. For this purpose, bioformulation of consortium was prepared and characterized for the viability up to 70 days of storage at 25±1oC. The consortium treated polymer samples were monitored through SEM and FT-IR spectroscopy. Analytical data revealed the biodeterioration potential of the developed consortium for PVC and LDPE, which could help in disposing the plastic waste.

Comparative biodegradation studies of cow dung modified epoxy with epoxy using an indigenously developed bacterial consortium

Thermoplastic-based polymers and their blends are recalcitrant in nature. Based on their extensive use, huge amount of polymeric waste is being produced annually, which impart serious threat on the natural ecosystem. Considering this scenario, it is needed to take some immediate actions to keep the ecosystem dynamic and secure. Therefore, this study was carried out in order to evaluate an indigenously developed bacterial consortium for the biodegradation of epoxy and a blend of epoxy with cow dung that is cow dung modified epoxy (CME). These polymers were preliminary screened against the used bacteria individually for determination of optimum concentration to utilize them as carbon source. For this purpose, the comparative in vitro biodegradation studies were carried out using the bacterial consortium. Relatively, better biodegradation potential of developed consortium was observed for epoxy in comparison to CME, as higher biomass and more sustained growth of consortium was obtained in the presence of epoxy. Further, the progressive in situ degradation of epoxy and CME films was also conducted in the presence and absence of consortium for three and six months under natural conditions. For this purpose, bioformulation of bacteria was used to inoculate the soil. The treated samples were analyzed for their comparative spectral, thermal and morphological changes. Thus, the present study reveals that the used bacterial strains have the potential to act upon epoxy and CME polymers and capable to impart changes in the surface morphology during incubation in soil. Key words: Epoxy, cow dung modified epoxy, biodegradation, bacterial consortium, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetry-differential thermal analysis (TG–DTG–DTA).

Comparative in situ PET biodegradation assay using indigenously developed consortia

A soil burial test was carried out to evaluate the biodegradation of polyethylene terephthalate under natural environment for a period of six months in presence of three different indigenously developed bacterial consortia. These consortia comprised of potential polymer-degrading bacterial cultures isolated from various waste disposal sites. The comparative biodegradation of PET samples in presence and absence of used consortia was monitored through Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). FTIR analysis implies structural changes in biodegraded PET samples unlike the control. The biodegradation is further substantiated by SEM which manifested the development of fissures and a sign of significant erosions which were progressive with the incubation time. Moreover, the DSC showed lowering of melting temperature (Tm) and heat of fusion (ΔHf) of biodegraded film samples suggesting their increased brittleness.