Plastic pollution has been a topic of grave concern worldwide due to major environmental, economic, health, and social impacts. Nevertheless, our society is far from casting plastics aside since they are essential for several applications (e.g. food packaging, automotive, electronics, building, and construction). Poly(terephtalate ethylene) (PET), an important synthetic polyester derived from petroleum, is extensively used in plastic packaging (mainly bottles and trays). Unfortunately, no greener polymer alternative has large-scale production to meet global demand. Consequently, plastic recycling is the most sustainable approach to manage the massive amounts of post-consumed PET materials, by recovering its monomeric units: terephthalic acid and ethylene glycol. However, current recycling methods are still costly, leading to more expensive reclaimed PET monomers than virgin ones obtained from fossil sources. Recently, PET upcycling emerged as a profitable strategy to value the reclaimed monomers by converting them into molecules with higher added value, enhancing the recycling process viability. In this review, we addressed all valuable commodities produced from the conversion of PET monomers catalyzed by microorganisms, as an eco-friendly process known as biological upcycling or bio-upcycling. We provided an outlook regarding potential markets and highlighted the benefits of the PET bio-upcycling route over the actual industrial production of each commodity. Moreover, we discussed different PET recycling methods employed to recover monomers prior to the bio-upcycling step, highlighting the pros and cons. Additionally, we addressed critical considerations about the major challenges regarding this novel recycling strategy, particularly in upscaling from lab-scale stage to real-world implementation.

Aqueous two-phase systems (ATPS) based on ionic liquids (IL) and deep eutectic solvents (DES) are ecofriendly choices and can be used to selectively separate compounds of interest, such as bioactive compounds. Bioactive compounds are nutrients and nonnutrients of animal, plant, and microbial origin that benefit the human body in addition to their classic nutritional properties. They can also be used for technical purposes in food and as active components in the chemical and pharmaceutical industries. Because they are usually present in complex matrices and low concentrations, it is necessary to separate them in order to increase their availability and stability, and ATPS is a highlighted technique for this purpose. This review demonstrates the application of ATPS based on IL and DES as a tool for recovering nonprotein bioactive compounds, considering critical factors, results and the most recent advances in this field. In addition, the review emphasizes the perspectives for expanding the use of nonconventional ATPS in purification systems, which consider the use of molecular modelling to predict experimental conditions, the investigation of diverse compounds in phase-forming systems, the establishment of optimal operational parameters, and the verification of bioactivities after the purification process.