Di-(2-ethylehxyl) phthalate (DEHP) is one of the most broadly representative phthalic acid esters (PAEs) used as a plasticizer in polyvinyl chloride (PVC) production, and is considered to be an endocrine-disrupting chemical. DEHP and its monoester metabolites are responsible for adverse effects on human health. An efficient DEHP-degrading bacterial strain Rhodococcus ruber YC-YT1, with super salt tolerance (0–12% NaCl), is the first DEHP-degrader isolated from marine plastic debris found in coastal saline seawater. Strain YC-YT1 completely degraded 100 mg/L DEHP within three days (pH 7.0, 30 °C). According to high-performance liquid chromatography–mass spectrometry (HPLC-MS) analysis, DEHP was transformed by strain YC-YT1 into phthalate (PA) via mono (2-ethylehxyl) phthalate (MEHP), then PA was used for cell growth. Furthermore, YC-YT1 metabolized initial concentrations of DEHP ranging from 0.5 to 1000 mg/L. Especially, YC-YT1 degraded up to 60% of the 0.5 mg/L initial DEHP concentration. Moreover, compared with previous reports, strain YC-YT1 had the largest substrate spectrum, degrading up to 13 kinds of PAEs as well as diphenyl, p-nitrophenol, PA, benzoic acid, phenol, protocatechuic acid, salicylic acid, catechol, and 1,2,3,3-tetrachlorobenzene. The excellent environmental adaptability of strain YC-YT1 contributed to its ability to adjust its cell surface hydrophobicity (CSH) so that 79.7–95.9% of DEHP-contaminated agricultural soil, river water, coastal sediment, and coastal seawater were remedied. These results demonstrate that R. ruber YC-YT1 has vast potential to bioremediate various DEHP-contaminated environments, especially in saline environments.

Despites lots of characterized microorganisms that are capable of degrading phthalic acid esters (PAEs), there are few isolated strains with high activity towards PAEs under a broad range of environmental conditions. In this study, Gordonia sp. YC-JH1 had advantages over its counterparts in terms of di(2-ethylhexyl) phthalate (DEHP) degradation performance. It possessed an excellent degradation ability in the range of 20–50 °C, pH 5.0–12.0, or 0–8% NaCl with the optimal degradation condition 40 °C and pH 10.0. Therefore, strain YC-JH1 appeared suitable for bioremediation application at various conditions. Metabolites analysis revealed that DEHP was sequentially hydrolyzed by strain YC-JH1 to mono(2-ethylhexyl) phthalate (MEHP) and phthalic acid (PA). The hydrolase MphG1 from strain YC-JH1 hydrolyzed monoethyl phthalate (MEP), mono-n-butyl phthalate (MBP), mono-n-hexyl phthalate (MHP), and MEHP to PA. According to molecular docking and molecular dynamics simulation between MphG1 and monoalkyl phthalates (MAPs), some key residues were detected, including the catalytic triad (S125-H291-D259) and the residues R126 and F54 potentially binding substrates. The mutation of these residues accounted for the reduced activity. Together, the mechanism of MphG1 catalyzing MAPs was elucidated, and would shed insights into catalytic mechanism of more hydrolases.

Reactive oxygen species (ROS) play dual roles in plant stress response, but how plants modulate the dual roles of ROS in stress response is still obscure. OsJAB1 (JUN-activation-domain-binding protein 1) encodes the rice CSN5 (COP9 signalsome subunit 5). This study showed that, similar to the Arabidopsis homolog gene CSN5B, OsJAB1-overexpressing (driven by a CaMV 35S promoter) plants (OEs) impaired rice salt stress tolerance; in contrast, OsJAB1-inhibited-expression (using RNA-interfering technology) plants (RIs) enhanced rice salt stress tolerance. Differing from CSN5B that negatively regulated ascorbate (Asc) biosynthesis, Asc content increased in OEs and decreased in RIs. ROS analysis showed that RIs clearly increased, but OEs inhibited ROS accumulation at the early stage of salt treatment; in contrast, RIs clearly decreased, but OEs promoted ROS accumulation at the late stage of salt treatment. The qPCR revealed that OEs decreased but RIs enhanced the expressions of ROS-scavenging genes. This indicated that OsJAB1 negatively regulated rice salt stress tolerance by suppressing the expression of ROS-scavenging genes. This study provided new insights into the CSN5 homologous protein named OsJAB1 in rice, which developed different functions during long-term evolution. How OsJAB1 regulates the Asc biosynthesis that coordinates the balance between cell redox signaling and ROS scavenging needs to be investigated in the future.