(227d) Technical Evaluation of Microbial Degradation of Polyethylene Terephthalate (PET) at a Laboratory Level.

Currently, the global production of plastic is around 359 million tons annually, and it is estimated that around 200 million tons of plastic are distributed in water sources, landfills, and other natural environments [1]. Among the wide range of plastic materials available today, polyethylene terephthalate (PET) is one of those with increasing production in the last 20 years, and it is expected to quadruple in the next 50 years [2]. However, the systems to contain, control, and recycle it have not followed the same trend, mainly because it is estimated that 1 million bottles are produced every minute worldwide, of which only 41% are recycled [3]. There are different alternatives for PET degradation, such as chemical, thermal, and physical alternatives, but these are not alternatives that cover a high demand such as landfill material. Moreover, they may include harmful substances or high energy consumption, and finally, they may affect the physicochemical properties of the polymer [1]. Therefore, research on PET degradation through biological means has been developed worldwide. In Colombia, the Bioprocesses and Reactive Flows research group (BIOFRUN) at the National University of Colombia is conducting technical evaluation of microbial degradation of Polyethylene Terephthalate (PET) at a laboratory level, working with a filamentous fungus and a bacterium, based on the hypothesis that achieving higher biomass production and performing the respective hydrolytic enzyme induction will result in greater enzyme production, with long-chain fatty acids being recommended inducers [4]. In the research conducted by the BIOFRUN group, it has been found that at the reactor level, agitation, a pH around to 9, oxygen saturation (around 40%), and a temperature between 20-24°C favor the production of biomass in small pellets, which reduces transfer problems in the reactor. Additionally, it has been found that PET, as the sole source of carbon, induces the hydrolytic enzyme, with degradation products such as terephthalic acid, bis-(2-hydroxyethyl) terephthalate (BHET), and monohydroxyethyl terephthalate (MHET) quantified in parts per million (ppm), which is why experiments are currently being conducted on PET pretreatments that favor the degradation of PET into its basic monomers and short-chain oligomers.

[1] V. Tournier et al., “An engineered PET depolymerase to break down and recycle plastic bottles,” Nature, vol. 580, pp. 219–219, 2020.

[2] I. Tiseo, “Global plastic production 1950-2020,” 2022. [Online]. Available: https://www.statista.com/statistics/282732/global-production-of-plastic…. [Accessed: 16-Jan-2022].

[3] S. Laville and M. Tayor, “A million bottles a minute: world’s plastic binge as dangerous,” The Guardian, London, 2017.

[4] D. Castro-Ochoa, C. Peña-Montes, and A. Farres, “Producción y caracaterísticas de cutinasas: Una alternativa interesante para biocatálisis a nivel industrial,” Rev. Espec. en Ciencias Químico-Biológicas, vol. 1, pp. 16–25, 2010.