Biochemical characterization and high-level production of oxidized polyvinyl alcohol hydrolase from Sphingopyxis sp. 113P3 expressed in methylotrophic Pichia pastoris

Performance and microbial community of an electric biological integration reactor (EBIR) for treatment of wastewater containing ibuprofen

Electric biological integration reactor (EBIR) was designed and built for the treatment of wastewater containing ibuprofen. This study evaluates the removal performance of EBIR by comparison with biological aerated filter (BAF), while also discussing the optimal operational parameters of EBIR within the context of the response surface methodology. The results indicate that EBIR exhibits higher average removal rates of ibuprofen, chemical oxygen demand (COD) and NH₄⁺-N, i.e. 93.48%, 86.72% and 85.19%, representing an increase by 61.59%, 14.57% and 10.49%, respectively, compared with BAF. The optimal conditions for EBIR were 12.73 A/m² current density (CD), 3.5 h hydraulic retention time and 0.08 mg/L influent ibuprofen concentration. In addition, microbial community structures were detected using an Illumina Miseq PE300 system, which were different at the phylum, class, and genus levels between EBIR and BAF. The microbial communities of EBIR, including mainly Trichococcus, Aeromonas, Saprospiraceae_uncultured, Thiobacillus, Aeromonas Flavobacterium, Sphingopyxis, Candidate_division_TM7_norank, Acinetobacter and physicochemical properties indirectly confirmed the excellent removal performance at 12.73 A/m² CD.

Structural insights into enzymatic degradation of oxidized polyvinyl alcohol

The ever-increasing production and use of polyvinyl alcohol (PVA) threaten our environment. Yet PVA can be assimilated by microbes in two steps: oxidation and cleavage. Here we report novel α/β-hydrolase structures of oxidized PVA hydrolase (OPH) from two known PVA-degrading organisms, Sphingopyxis sp. 113P3 and Pseudomonas sp. VM15C, including complexes with substrate analogues, acetylacetone and caprylate. The active site is covered by a lid-like β-ribbon. Unlike other esterase and amidase, OPH is unique in cleaving the CC bond of β-diketone, although it has a catalytic triad similar to that of most α/β-hydrolases. Analysis of the crystal structures suggests a double-oxyanion-hole mechanism, previously only found in thiolase cleaving β-ketoacyl-CoA. Three mutations in the lid region showed enhanced activity, with potential in industrial applications.