Whole-cell biocatalysis using the Acidovorax sp. CHX100 Δ6HX for the production of ω-hydroxycarboxylic acids from cycloalkanes

Acidovorax PSJ13, a novel, efficient polyacrylamide-degrading bacterium by cleaving the main carbon chain skeleton without the production of acrylamide

Given the environmental challenge caused by the wide use of polyacrylamide (PAM), an environmental-friendly treatment method is required. This study demonstrates the role of Acidovorax sp. strain PSJ13 isolated from dewatered sludge in efficiently degrading PAM. To be specific, the strain PSJ13 can degrade 51.67% of PAM in 96 h (2.39 mg/(L h)) at 35 °C, pH 7.5 and 5% inoculation amount. Besides, scanning electron microscope, X-ray photoelectron spectroscopy, liquid chromatography-mass spectrometry and high-performance liquid chromatography were employed to analyze samples, and the nitrogen present in the degradation products was investigated. The results showed that the degradation of PAM by PSJ13 started from the side chain and then mainly the -C-C- main chain, which produced no acrylamide monomers. As the first study to report the role of Acidovorax in efficiently degrading PAM, this work may provide a solution for industries that require PAM management.

Insights into bacterial community metatranscriptome and metabolome in river water influenced by palm oil mill effluent final discharge

AIMS

This study aimed to investigate the effect of palm oil mill effluent (POME) final discharge on the active bacterial composition, gene expression, and metabolite profiles in the receiving rivers to establish a foundation for identifying potential biomarkers for monitoring POME pollution in rivers.

METHODS AND RESULTS

The POME final discharge, upstream (unpolluted by POME), and downstream (effluent receiving point) parts of the rivers from two sites were physicochemically characterized. The taxonomic and gene profiles were then evaluated using de novo metatranscriptomics, while the metabolites were detected using qualitative metabolomics. A similar bacterial community structure in the POME final discharge samples from both sites was recorded, but their composition varied. Redundancy analysis showed that several families, particularly Comamonadaceae and Burkholderiaceae [Pr(>F) = 0.028], were positively correlated with biochemical oxygen demand (BOD5) and chemical oxygen demand (COD). The results also showed significant enrichment of genes regulating various metabolisms in the POME-receiving rivers, with methane, carbon fixation pathway, and amino acids among the predominant metabolisms identified (FDR < 0.05, PostFC > 4, and PPDE > 0.95). This was further validated through qualitative metabolomics, whereby amino acids were detected as the predominant metabolites.

CONCLUSIONS

The results suggest that genes regulating amino acid metabolism have significant potential for developing effective biomonitoring and bioremediation strategies in river water influenced by POME final discharge, fostering a sustainable palm oil industry.

Toward Kilogram-Scale Peroxygenase-Catalyzed Oxyfunctionalization of Cyclohexane

Mol-scale oxyfunctionalization of cyclohexane to cyclohexanol/cyclohexanone (KA-oil) using an unspecific peroxygenase is reported. Using AaeUPO from Agrocybe aegerita and simple H₂O₂ as an oxidant, cyclohexanol concentrations of more than 300 mM (>60% yield) at attractive productivities (157 mM h^-1, approx. 15 g L^-1 h^-1) were achieved. Current limitations of the proposed biooxidation system have been identified paving the way for future improvements and implementation.

Engineering polyester monomer diversity through novel pathway design

Polyesters composed of hydroxy acids (HAs) and diols serve many material niches and are invaluable to our daily lives. However, their traditional synthesis from petrochemicals creates many environmental concerns. Metabolically engineered microorganisms have been leveraged for the industrially competitive production of a few polyesters with properties that limit their application. Designing new metabolic pathways to polyester building blocks is essential to broadening material property diversity and improving carbon and energy usage of current bioproduction schemes. This review focuses on recently developed pathways to HAs and diols. Specifically, new pathways to 2,3- and ω-Hydroxy acids, as well as C3-C4 and medium-chain-length diols, are discussed. Pathways to the same compound are compared on the basis of criteria such as energy usage, number of pathway steps, and titer. Finally, suggestions for improvements and next steps for each pathway are also discussed.

Role of types and dosages of cations with low valance states on microalgal-bacterial symbiosis system treating wastewater

This study investigated the roles of cations with low valance states, including Mg²⁺, K⁺ and Li⁺, on microalgal-bacterial symbiosis (MABS) system treating wastewater. Results showed that Mg²⁺ and K⁺ improved pollutants removal at dosages of less than 1 mM, and a further increase led to poorer performances. Conversely, Li⁺ inhibited pollutants removal. Mechanism study indicated Mg²⁺ and K⁺ with dosages of 10 mM and Li ⁺ inhibited the activities of MABS biomass (especially Chlorella), with bad absorption efficiencies of 20.64 %, 13.65 % and lower than 10 %, leading to more extracellular polymeric substances production. Larger ions' charge density resulted in larger attraction of water molecules, contributing to the decreased distance between microalgae cells and increased biomass aggregation. Both these two impacts led to the order of impact degree on MABS aggregates: Mg²⁺ > Li⁺ > K⁺. The findings can present some new perspectives on assessing effects of cations on MABS system.

Cell-Free Biosynthesis of ω-Hydroxy Acids Boosted by a Synergistic Combination of Alcohol Dehydrogenases

The activity orchestration of an unprecedented cell-free enzyme system with self-sufficient cofactor recycling enables the stepwise transformation of aliphatic diols into ω-hydroxy acids at the expense of molecular oxygen as electron acceptor. The efficiency of the biosynthetic route was maximized when two compatible alcohol dehydrogenases were selected as specialist biocatalysts for each one of the oxidative steps required for the oxidative lactonization of diols. The cell-free system reached up to 100 % conversion using 100 mM of linear C₅ diols and performed the desymmetrization of prochiral branched diols into the corresponding ω-hydroxy acids with an exquisite enantioselectivity (ee>99 %). Green metrics demonstrate superior sustainability of this system compared to traditional metal catalysts and even to whole cells for the synthesis of 5-hydroxypetanoic acid. Finally, the cell-free system was assembled into a consortium of heterogeneous biocatalysts that allowed the enzyme reutilization. This cascade illustrates the potential of systems biocatalysis to access new heterofunctional molecules such as ω-hydroxy acids.

Contribution of Fermentation Technology to Building Blocks for Renewable Plastics

Large-scale worldwide production of plastics requires the use of large quantities of fossil fuels, leading to a negative impact on the environment. If the production of plastic continues to increase at the current rate, the industry will account for one fifth of global oil use by 2050. Bioplastics currently represent less than one percent of total plastic produced, but they are expected to increase in the coming years, due to rising demand. The usage of bioplastics would allow the dependence on fossil fuels to be reduced and could represent an opportunity to add some interesting functionalities to the materials. Moreover, the plastics derived from bio-based resources are more carbon-neutral and their manufacture generates a lower amount of greenhouse gasses. The substitution of conventional plastic with renewable plastic will therefore promote a more sustainable economy, society, and environment. Consequently, more and more studies have been focusing on the production of interesting bio-based building blocks for bioplastics. However, a coherent review of the contribution of fermentation technology to a more sustainable plastic production is yet to be carried out. Here, we present the recent advancement in bioplastic production and describe the possible integration of bio-based monomers as renewable precursors. Representative examples of both published and commercial fermentation processes are discussed.