An asphaltene sample from a light Arabian crude oil was characterized using several analytical techniques, such as thermogravimetric analysis, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and elemental analysis. The results showed that the sample has a high sulfur content and highly condensed aromatic compounds and the average molecular structure is predominantly of continental/island type; however, the presence of a significant amount of methylene carbons in long alkyl chains is clear. A diffusion-ordered spectroscopy nuclear magnetic resonance experiment (DOSY-NMR) was carried out to detect the presence of asphaltene aggregates, evaluate their size, and shed light on the presence of maltenic occluded species and entrained residual solvent. In the DOSY spectrum, some sample signals were attributed to non-asphaltenic molecules, showing that it is possible to achieve key features of the sample complexity in “one shot”.

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Biological recycling of PET waste has been extensively investigated recently to tackle plastic waste pollution, and ethylene glycol (EG) is one of the main building blocks recovered from this process. Wild-type Yarrowia lipolytica IMUFRJ 50682 can be a biocatalyst to biodepolymerize PET. Herein, we report its ability to perform oxidative biotransformation of EG into glycolic acid (GA): a higher value-added chemical with varied industrial applications. We found that this yeast tolerates high EG concentrations (up to 2 M) based on maximum non-inhibitory concentration (MNIC) tests.Whole-cell biotransformation assays using resting yeast cells showed GA production uncoupled to cell growth metabolism, and 13 C nuclear magnetic resonance (NMR) analysis confirmed GA production. Moreover, higher agitation speed (450 vs. 350 rpm) resulted in a 1.12-fold GA production improvement (from 352 to 429.5 mM) during Y. lipolytica cultivation in bioreactors after 72 h. GA was constantly accumulated in the medium, suggesting that this yeast may also share an incomplete oxidation pathway (i.e., it is not metabolized to carbon dioxide) as seen in acetic acid bacterial group.Additional assays using higher chain-length diols (1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol) revealed that C4 and C6 diols were more cytotoxic, suggesting that they underwent different pathways in the cells. We found that this yeast consumed extensively all these diols, however, 13 C NMR analysis from supernatant identified solely the presence of 4-hydroxybutanoic acid from 1,4-butanediol, along with GA from EG oxidation. Findings reported herein reveal a potential route for PET upcycling to a higher value-added product.

BACKGROUND:The global concern of plastic pollution in the environment has consistently been emerging in the past years. As one of the main polymers constituting single-use products, poly(ethylene terephthalate) (PET) is found in a plethora of packages for diverse sectors, and its recycling has been broadly addressed. However, other relevant industrial PET wastes have not been under investigation for recycling purposes, such as the polyester mooring lines (PMLs) used to anchor offshore oil and gas floating platforms. In this study, the fibers from either new or used PMLs were characterized according to different techniques (differential scanning calorimetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, nuclear magnetic resonance and scanning electron microscopy-energy-dispersive X-ray spectroscopy), which allowed the interpretation of their chemical and thermal properties. The fibers were then used in depolymerization reactions under the catalysis of the cutinase enzyme from Humicola insolens and under different process conditions (fiber length, buffer composition, enzyme dosage, temperature, pH).RESULTS: Characterization of PMLs revealed inorganic incrustation in the external fibers, and very similar crystallinity degrees. The molecular weight, on the other hand, was found to be lower in new mooring lines (27 489 g mol −1 ) as compared to used mooring lines (35 813-36 785 g mol −1 ). Throughout depolymerization reactions, a total concentration increase of terephthalic acid of up to 7.4 times (2593 ∼mol L -1 ) was achieved.CONCLUSION: The results proved the concept that the studied cutinase can act on PET chains. To the best of our knowledge, this is the first report to describe an enzyme-catalyzed depolymerization of PET from mooring lines, and the results add relevant knowledge for a circular economy of plastic products.