Sun Moon University

Plastic pollution poses a significant threat to the Arctic ecosystem, primarily due to long-distance transport and localized anthropogenic activities. This study examines the plastic-degrading bacteria from the Arctic, with a focus on Pseudomonas sp. PAMC26590, which degrades mono(2-hydroxyethyl) terephthalate (MHET). Genomic analysis of this strain revealed a putative MHET hydrolase gene involved in MHET degradation, as supported by in-silico methods. The strain has a 6.2 Mb circular chromosome with 60 % GC content, 5287 coding genes, 64 tRNAs, and 16 rRNAs. Under the optimized conditions (20 °C, pH 7.0, mineral salt medium), Pseudomonas degraded 58.33 % of MHET (83 ng/mL) within 7 days, demonstrating cold-adapted degradation capability. Thus, we present our discovery of the Arctic strain Pseudomonas sp. PAMC26590 has shown the ability to degrade MHET at low temperatures for the first time. Furthermore, recombinant MHET hydrolase showed 79 % biodegradation activity at pH 8.0 and 25 °C. Molecular docking revealed a strong binding affinity (ΔG = -6.67 kcal/mol) mediated by the catalytic residues Ser199, His457, and Asp416, supported by stabilizing van der Waals interactions, which suggests a biologically plausible binding mode. Molecular dynamics (MD) simulations and MM-GBSA calculations confirmed structural stability and energetically favorable binding (ΔGbind = -65.42 kcal/mol), reinforcing the ligand's potential role in the catalytic mechanism of MHET hydrolase.

This study identify the featured topics of studies related to digital twin (DT) and healthcare through Structural Topic Modeling (STM). Papers on the DT in healthcare were gathered from five databases between 2018 and 2024. An STM model was developed, and the best topics were selected based on semantic coherence, lower bound, and held-out likelihood. Eight topics were emerged from the literature. The integration of advanced technologies, led by DT, is revolutionizing healthcare and manufacturing by delivering more efficient, personalized, and innovative solutions.

Flavonoids undergo O-methylation, a modification catalyzed by O-methyltransferase (OMT), which transfers a methyl group from S-adenosyl-_L-methionine (AdoMet/SAM) to nucleophilic acceptors in flavonoid structures. This study focused on an OMT gene isolated from Streptomyces sp. KCCM12257 that was cloned and expressed in Escherichia coli C41. The recombinant class I methyltransferase (36.12 kDa) utilized Mg²⁺ as a cofactor for substrate binding, efficiently methylating various flavonoid substrates at pH 8.0. However, other metal co-factors, including divalent and monovalent ions, generally diminished the enzyme's activity, apart from Ca²⁺. To enhance the availability of SAM and improve biotransformation yields, we co-expressed the OMT12257 and metK genes from E. coli, achieving the production of 120 mg/L of 5-O-methylresveratrol, 75 mg/L of 3'-O-methyldiosmetin, 60 mg/L of 7-O-methylkaempferol (rhamnocitrin), and 85 mg/L of methylated luteolin derivatives. Analysis of the methylation patterns revealed that substrates such as luteolin, diosmetin, and resveratrol underwent double methylation at the A and B rings, whereas other flavonoids were singly methylated. Notably, the enzymatically methylated derivatives of diosmetin and resveratrol exhibited significant anti-tuberculosis activity, with the lowest Minimum Inhibitory Concentration (MIC) of 25 μg/mL, marking the first report of such activity. This study provides valuable insights into the enzymatic methylation of flavonoids, revealing the potential for developing bioactive compounds.