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A solution for plastic waste pollution

Periodic Reporting for period 1 - SOLFORPLAS (A solution for plastic waste pollution )

Reporting period: 2019-09-02 to 2021-09-01

Since the 1970s, the mismanagement of plastic waste has been increasingly threatening our health and environment. What was considered a mere aesthetic problem only a few years ago is today a real global environmental problem. Today nearly everyone, everywhere, every day comes into contact with plastics – especially plastic packaging. While delivering many benefits, the current plastics economy has drawbacks that are becoming more apparent by the day. Rather than been reduced, plastic production is growing exponentially. By 2050, the estimation of plastic waste in landfills or in the natural environment verges on 12 billion metric tons, if current production and waste management trends continue. Societies are raising awareness about this concern, although our dependency makes nearly impossible to imagine a world without plastics. This urges for a solution making plastic production and degradation sustainable. To date, important efforts have been made to isolate and identify unique microorganisms capable of utilizing plastics as a carbon source. Although there is empirical evidence of it, the rates of biodegradation are still very low. In the SOLFORPLAS project, we applied cutting-edge biology tools, including fermentation and analytical processes, together with state-of-the-art methods in industrial microbiology research, to investigate plastic biodegradation using a highly optimized strategy that combines an extruder and a bioreactor. The innovative combined strategy integrates physical, chemical and biological treatments, which mimic the whole biodegradation process taking place in worms, as a solution for plastic pollution.
The polymer tested in SOLFORPLAS, polyethylene, has been successfully pre-degraded using physico-chemical treatments, which are in addition environmentally friendly. These excluded the extruder technology for the moment, which was found to induce changes in the polymer structure only at extremely high temperatures, representing thus a less sustainable alternative. The physico-chemical treatments finally applied successfully reduced the molecular weight and increased the carbonyl index (oxidation) of the polymer, indicating that its long carbon chains were effectively broken down, and its chemical structure oxidized. Scanning Electron Microscopy (SEM) images revealed clear fissures in this pre-treated material, providing a detailed characterization of such an early degradation process. This represents a crucial milestone within the Project SOLFORPLAS, since no microorganism can degrade polyethylene by itself, unless the polymer is previously pretreated before exposed to the microorganisms.
We next characterized the biological degradation of polyethylene, by screening in vitro 32 microorganism(s) including bacteria, yeasts and fungi. Based on our results, yeasts represented the best candidates for polymer degradation. In particular, five yeasts were particularly promising, notable for their ability to degrade lipids and grow on n-paraffins as sole carbon source. All the analyzed parameters confirmed that these yeasts survived in the presence of polyethylene as the sole carbon source for a month, preferring the pre-treated material than the non-modified polyethylene. Although we did not detect a reduced molecular weight or a modified FTIR spectra of the polymer, yeast adhesion to the non-modified and especially to the modified polyethylene was observed by fluorescence microscopy and SEM. More importantly, this attachment led to small but significant losses in absolute plastic weight.
SOLFORPLAS project have contributed to address one of the biggest environmental problems that humans are facing in this century, with direct applications in the industries of plastic recycling and single-cell protein production. The project established a combined strategy to carry out plastic biodegradation.
Characterizing and optimizing the most effective processes for plastic degradation will undoubtedly bear commercial interest for industries, while the end-product following biodegradation will be biomass in the form of single-cell protein, a green sustainable alternative to supplement human diets or animal feeding (source of proteins in green chemistry), rounding up a process of circular economy.
Our contribution to solve this major problem is thus expected to have a major impact, in the form of high-profile publications, attracting media attention and creating social awareness of the problem, including a gender perspective of the associated health problems. In addition to publications, applied research may lead to patentable knowledge, which may have an important turning back to the industry.
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