Yuji Aso

Poly(ethylene terephthalate) (PET) is a widely used commodity polymer owing to its low cost, excellent mechanical properties, and high processability. Chemical modification of PET surfaces to impart specific functionalities represents an effective strategy for transforming PET into high-value-added materials without altering its bulk properties. In this study, we investigated the surface functionalization of PET substrates using surface-initiated atom transfer radical polymerization (SI-ATRP). ATRP initiation sites were introduced onto PET surfaces through mild surface hydrolysis followed by polyethyleneimine coating. To further enhance the grafting density, an inimer-based strategy was employed, in which a bifunctional monomer containing both a polymerizable group and a latent initiation site was used to form hyperbranched polymer structures on the PET surface, thereby amplifying the number of active initiation sites. Using these modified PET substrates, SI-ATRP of functional methacrylate monomers was successfully carried out. Grafting of poly(2,2,2-trifluoroethyl methacrylate) imparted highly hydrophobic surface properties, yielding water contact angles above 120°, whereas grafting of poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride) produced hydrophilic surfaces with contact angles below 20°. Surface characterization by X-ray photoelectron spectroscopy confirmed successful graft polymerization and effective surface coverage. While the macroscopic wettability was primarily governed by the chemical nature of the grafted polymers, the inimer-based initiation-site amplification significantly enhanced the surface electrostatic properties of the polycationic polymer–grafted surfaces, increasing the ζ-potential from approximately +20 mV to over +100 mV. Antibacterial tests using Escherichia coli K-12 as a model bacterium demonstrated that PET substrates grafted with poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride) exhibited clear contact-active antibacterial activity, achieving up to 2-log reduction in viable bacterial counts after 3 h of contact incubation. These results highlight the importance of molecular-level control of grafting architecture and surface electrostatic properties in the design of functional antibacterial PET surfaces.

Urocanic acid (UA), an intermediate in L-histidine catabolism, is a unique heterocyclic compound with various bioactivities. This study demonstrates UA production from glucose as a carbon source using engineered Corynebacterium ammoniagenes. The wild-type strain C. ammoniagenes NBRC 12071 was subjected to disruption of hutU, which encodes urocanate hydratase. After 7 days of cultivation with a minimum medium containing 2% glucose, the resulting strain MM1 produced 2.0 ± 0.1 mg/L UA with 0.29 ± 0.00 mg/g-cells/day specific production rate, while the wild-type produced a trace amount of UA. This indicated that the disruption arrested UA consumption. MM1 was spontaneously mutated with N-methyl-N’-nitro-N-nitrosoguanidine, forming 3-amino-1,2,4-triazole-resistant strains, some of which produced 0.16–0.29 g/L UA from 2% glucose. This indicates that the disruption of hutU was useful for constructing spontaneous mutants that produce UA. To improve UA production, hutH, which encodes histidine ammonia lyase, was overexpressed in MM1 using the strong C. ammoniagenes promoter Prpl21. After 7 days of cultivation, the resulting strain MM5 produced 7.7 ± 0.3 mg/L UA with 1.73 ± 0.12 mg/g-cells/day specific production rate. This indicates that overexpression strengthened the L-histidine catabolism. The use of a semi-synthetic medium would help improve the growth of engineered strains. To the best of our knowledge, this is the first report on UA production by engineered C. ammoniagenes.

In this study, a bio-based vinylidene monomer, itaconic acid (IA), produced by a fungus Aspergillus terreus NBRC 6123 was polymerized in the culture. The inhibition of IA polymerization by the culture components was eased by extraction with 4-methyltetrahydropyran (4mTHP). The extraction with 4mTHP for 4 days under aerobic condition resulted in IA production at 67.9 g/L (522 mM) in the organic phase from 180 g/L glucose. Interestingly, 4mTHP did not affect to the glucose consumption and respiration of A. terreus. IA polymerization in 4mTHP for 72 h using 400 mM IA and 1 mM 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) as a radical initiator under anaerobic condition by N₂ gas purging resulted in that the IA conversion, and the weight-averaged molecular weight (Mw) and the molecular weight distribution (MWD) of the synthesized polyitaconic acid (polyIA) were 11.5%, 79.8 × 10³ g/mol, and 1.26, respectively. The respiration by the IA producer itself was used to remove the residual oxygen in the flask by sealing after the IA production. Colorimetric evaluation with a redox indicator, resazurin, revealed that an anaerobic condition which is suitable for the IA polymerization can be accomplished by just incubation for 1 day after the sealing. The synthesis of polyIA from glucose in the same flask with 4mTHP was demonstrated, resulting in that the IA conversion, and Mw and MWD of the synthesized polyIA were 13.8%, 9.1 × 10³ g/mol, and 1.24, respectively, when 47.1 g/L (362 mM) IA was produced by the extraction for 3 days. To our knowledge, this is the first demonstration of radical polymerization of vinylidene monomer in microbial cultures. Graphical abstract

Polymers bearing hydrophobic amino acid moieties were synthesized, and their binding affinities with wood lignin were investigated. The polymers bearing tryptophan and phenylalanine moieties were observed to exhibit high binding affinity.

Objectives A bipolar membrane microbial fuel cell (bMFC) is used to generate electricity using cellulose in phosphate buffer solution as fuel, and the mechanism of electricity generation is elucidated from five reference experiments. Results The bMFC was operated for 20 days using cellulose as fuel and Cellulomonas fimi. In the first reference experiment, no microorganism was used. In the second experiment, a cation-exchange membrane was used instead of a bipolar membrane. In the third experiment, the bipolar membrane was used in the opposite orientation as in the main experiment. In the fourth experiment, D₂O was used instead of H₂O in the cathode chamber. In the final experiment, the tris-maleate buffer was used instead of a phosphate buffer. Sufficient power generation did not occur in either reference experiment. Conclusions The bMFC continuously generated electricity for 20 days, and elucidated H⁺ and OH⁻ react in bipolar membrane, where the counter cation of dihydrogen phosphate served as the final electron acceptor.

Itaconic acid (IA) and its derivatives produced by fungi have significant potential as industrial feedstocks. We recently developed a method for the detection of these compounds based on their terminal C–C double bonds. However, the presence of reducing agents, such as glucose and other fungal metabolites, leads to undesirable side reactions, and consequently, deteriorates the detection specificity. Therefore, we developed a fluorescence detection method for IA and its derivatives underpinned by a photoclick reaction. The photoclick reaction between conjugated IA and 5-(4-methoxyphenyl)-2-phenyl-2H-tetrazole under UV irradiation affords a fluorescent product. No fluorescence was detected when succinic acid was subjected to the reaction, indicating that a terminal C–C double bond is required to induce fluorescence. Optimal reaction conditions were determined to be a combination of 80% final dimethyl sulfoxide concentration, 30-s UV irradiation, and a pH of 2. Two weeks after the reaction at 4 °C, 89.0% of the initial intensity was retained, indicating that the reaction product was relatively stable. Glucose and kojic acid did not induce fluorescence after the reaction, indicating that these reducing agents did not affect fluorescence. IA was detected in a culture of Aspergillus terreus, and its quantification using the photoclick reaction was in agreement with the results obtained using high-performance liquid chromatography analysis. Interestingly, the IA derivative avenaciolide present in submillimolar quantities was also detectable in a culture of Aspergillus avenaceus using this method. The established method will enable the development of high-throughput screening methods to identify fungi that produce IA and its derivatives. Graphical abstract

Glyoxylates are essential intermediates in several metabolic pathways and have a broad range of industrial applications. In this study, we propose a novel method for producing glyoxylate from glucose using engineered Escherichia coli BW25113. To direct the production of glyoxylate from glucose, malate synthase A (aceB), malate synthase G (glcB), glyoxylate carboligase (gcl), and glyoxylate/hydroxypyruvate reductase A (ycdW) genes were disrupted, and the glyoxylate shunt was reinforced in the disruptants by the overexpression of citrate synthase (gltA) and isocitrate lyase (aceA). In flask cultivation using M9 medium supplemented with 1% glucose, the disruptant E. coli BW25113 ΔaceB ΔglcB Δgcl ΔycdW produced 0.93 ± 0.17 g/L of glyoxylate. Further overexpression of gltA and aceA in the disruptant resulted in an improvement in glyoxylate production to 1.15 ± 0.02 g/L. By expressing a heterologous gene, pyc, in the engineered E. coli, the accumulation of intracellular oxaloacetate remarkably improved, leading to glyoxylate production of up to 2.42 ± 0.00 g/L with specific productivity at 4.22 ± 0.09 g/g-cell. To date, this is the highest reported titer and specific productivity of glyoxylate in E. coli.