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Poly(ethylene terephthalate) (PET) is one of the most consumed plastics in the world. The development of efficient technologies for its depolymerization for monomers reuse is highly encouraged, since current recycling rates are still very low. In this study, 16 commercial lipases and cutinases were evaluated for their abilities to catalyze the hydrolysis of two PET samples. Humicola insolens cutinase showed the best performance and was then used in reactions on other PET sources, solely or in combination with the efficient mono(hydroxyethyl terephthalate)-converting lipase from Candida antarctica. Synergy degrees of the final titers of up to 2.2 (i.e., more than double of the concentration when both enzymes were used, as compared to their use alone) were found, with increased terephthalic acid formation rates, reaching a maximum of 59,989 µmol/L (9.36 g/L). These findings open up new possibilities for the conversion of post-consumer PET packages into their minimal monomers, which can be used as drop in at existing industrial facilities.

The anti-corrosion effect and the antimicrobial activity of lemongrass essential oil (LEO) against the planktonic and sessile growth of a sulfate reducing bacterium (SRB) were evaluated. Minimum inhibitory concentration (MIC) of LEO and its major component, the citral, was 0.17 mg ml-1. In addition, both LEO and citral showed an immediate killing effect against SRB in liquid medium, suggesting that citral is responsible for the antimicrobial activity of LEO against SRB. Transmission electron microscopy revealed that the MIC of LEO caused discernible cell membrane alterations and formed electron-dense inclusions. Neither biofilm formation nor corrosion was observed on carbon steel coupons after LEO treatment. LEO was effective for the control of the planktonic and sessile SRB growth and for the protection of carbon steel coupons against biocorrosion. The application of LEO as a potential biocide for SRB growth control in petroleum reservoirs and, consequently, for souring prevention, and/or as a coating protection against biocorrosion is of great interest for the petroleum industries.

Biogenic souring and microbial-influenced corrosion is a common scenario in water-flooded petroleum reservoirs. Water injection systems are continuously treated to control bacterial contamination, but some bacteria that cause souring and corrosion can persist even after different treatments have been applied. Our aim was to increase our knowledge of the bacterial communities that persist in the water injection systems of three offshore oil platforms in Brazil. To achieve this goal, we used a culture-independent molecular approach (16S ribosomal RNA gene clone libraries) to analyze seawater samples that had been subjected to different treatments. Phylogenetic analyses revealed that the bacterial communities from the different platforms were taxonomically different. A predominance of bacterial clones affiliated with Gammaproteobacteria, mostly belonging to the genus Marinobacter (60.7%), were observed in the platform A samples. Clones from platform B were mainly related to the genera Colwellia (37.9%) and Achromobacter (24.6%), whereas clones obtained from platform C were all related to unclassified bacteria. Canonical correspondence analyses showed that different treatments such as chlorination, deoxygenation, and biocide addition did not significantly influence the bacterial diversity in the platforms studied. Our results demonstrated that the injection water used in secondary oil recovery procedures contained potentially hazardous bacteria, which may ultimately cause souring and corrosion.

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