Plastics are highly durable and widely used materials. Current methodologies of plastic degradation, elimination, and recycling are flawed. In recent years, biodegradation (the usage of microorganisms for material recycling) has grown as a valid alternative to previously used methods. The evolution of bioengineering techniques and the discovery of novel microorganisms and enzymes with degradation ability have been key. One of the most produced plastics is PET, a long chain polymer of terephthalic acid (TPA) and ethylene glycol (EG) repeating monomers. Many enzymes with PET degradation activity have been discovered, characterized, and engineered in the last few years. However, classification and integrated knowledge of these enzymes are not trivial. Therefore, in this work we present a summary of currently known PET degrading enzymes, focusing on their structural and activity characteristics, and summarizing engineering efforts to improve activity. Although several high potential enzymes have been discovered, further efforts to improve activity and thermal stability are necessary.

Pseudomonas aeruginosa is an opportunistic Gram-negative bacterium responsible for acute and chronic infections in planktonic state or in biofilms. The sessile structures are known to confer physical stability, increase virulence, and work as a protective armor against antimicrobial compounds. P. aeruginosa can control the expression of genes, population density, and biofilm formation through a process called quorum sensing (QS), a rather complex and hierarchical system of communication. A recent strategy to try and overcome bacterial resistance is to target QS proteins. In this study, a combined multi-level computational approach was applied to find possible inhibitors against P. aeruginosa QS regulator protein MvfR, also known as PqsR, using a database of approved FDA drugs, as a repurposing strategy. Fifteen compounds were identified as highly promising putative MvfR inhibitors. On those 15 MvfR ligand complexes, molecular dynamic simulations and MM/GBSA free-energy calculations were performed to confirm the docking predictions and elucidate on the mode of interaction. Ultimately, the five compounds that presented better binding free energies of association than the reference molecules (a known antagonist, M64 and a natural inducer, 2-nonyl-4-hydroxyquinoline) were highlighted as very promising MvfR inhibitors.

The emergence of multi-drug resistant bacteria in the past decades has become one of the major public health issues of our time. One of the main mechanisms of resistance and persistence of bacteria is their ability to form biofilms. Quorum-sensing (QS) is one of the main mechanisms of biofilm formation. Interfering with the QS cascade constitutes a non-antibiotic strategy to reduce biofilm formation and affect bacterial resistance. In Pseudomonas aeruginosa, QS takes place by four different systems, which start with the activation of transcriptional receptor LasR. This receptor is stabilized by C12-HSL. In this work, we have optimized and employed a multi-level in silico protocol to identify promising LasR inhibitors, combining different computer aided drug design techniques such as molecular docking, virtual screening, molecular dynamics and free energy calculations. The protocol was optimized using all 21 available LasR X-ray structures, 7 docking scoring functions, and a library of 90 active and 4500 inactive compounds. The optimized protocol was used to scan 294 498 chemically distinct compounds from 5 different databases, of which 30 compounds were further studied by molecular dynamics and free energy calculations and resulted in 8 possible QS inhibitors with promising ADME properties and binding affinity.

We described the catalytic mechanism of IsPETase, a polyethylene-terephthalate degrading enzyme. The reaction was found to progress in four steps, divided in two events: formation of the first transition intermediate and hydrolysis of the adduct.