The microbial deterioration of plastics

Considerable amounts of single‐use plastics are discarded and persist in our natural environment for an extended period of time. This research project investigates the deterioration processes of plastics that are sold commercially in Malta, with a special emphasis on plastic bottles, containers and shopping bags.

A number of experiments are being conducted to compare the natural deterioration of different plastics in the soil and marine environments to that carried out by particular microbes in vitro. Parameters indicative of surface appearance, polymer strength and composition are being measured before, throughout and after treatment. This study aims to monitor changes in the plastic films due to biological, as well as biophysical and biochemical degradation.

This research is particularly relevant to the present situation in Malta, where landfills are expected to reach full capacity within the next few years, and safe alternatives are thus being sought as a solution to the waste management crisis. The microbes used in this study are nonpathogenic and the end products of microbial deterioration are nontoxic.

This interdisciplinary study is being led by Dr Gabrielle Zammit and involves the participation and training of both undergraduate and postgraduate students enrolled at the university, who will acquire invaluable new skills pertaining to both microbiology and materials science.

Results from this study will be disseminated to the general public by the research team, in an effort to create awareness regarding the deterioration of plastics in our natural environment and possible safe biotechnological solutions to the problem.

This research is supported by The Gasan Foundation 

‘Polyethylene terephthalate (PET) is one of the most common plastics in use worldwide. Recycling rates reach 30% in the US and 50% in the EU. In Malta, the rate is lower, and a considerable amount of the PET is discarded. During its manufacture, small amounts of various additives are used to confer particular properties to the plastic that depend on its end use. Both low and high density polyethylene plastics (LDPE, HPPE) are used commercially in Malta due to the fact that these plastics are cheap and easily processed. Different types of PE are derived from natural gas or crude oil under the right conditions of temperature, pressure and catalysis.

Even though, in general, PET and PE plastics are considered resistant to breakdown in the natural environment, recently, a number of microbes have shown promise in degrading these polymers.