Silk sericin (SS), a biocompatible protein derived from silkworms, exhibits valuable properties for medicinal applications, including antioxidant activity and cell growth support. However, their rapid degradation limits their practical use. This study introduces silver ions (Ag⁺) as a dual-function cross-linking agent to enhance the structural and functional properties of SS-based hydrogels. The incorporation of Ag⁺ stabilized the hydrogel network through dityrosine cross-links and coordination bonds with SS amino acid side chains, significantly improving hydrolytic and enzymatic resistance. Hydrogels cross-linked with 1 mM Ag⁺ demonstrated optimal performance, retaining excellent structural integrity while preserving the cytocompatibility and antioxidant activity of SS. These hydrogels also exhibited broad-spectrum antimicrobial activity against bacteria (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and methicillin-resistant S. aureus), fungus (Aspergillus niger), and yeast (Candida albicans). Higher Ag⁺ concentrations, however, increased the cytotoxicity without enhancing the antimicrobial efficacy. This study highlights the potential of Ag⁺ cross-linked SS-based hydrogels as scalable, multifunctional 3D structures for antimicrobial applications.

Two new marine actinobacteria, designated as J2-1^T and J2-2^T, were isolated from a coral, Favites pentagona, collected from Rayong Province, Thailand. The taxonomic positions of the two strains were identified based on polyphasic taxonomy. Based on morphological characteristics and chemotaxonomy, strains J2-1^T and J2-2^T were identified as members of the genus Streptomyces and Kineosporia , respectively. Strains J2-1^T and J2-2^T showed the highest 16S rRNA gene sequence similarity to Streptomyces broussonetiae T44^T (98.62 %) and Kineosporia babensis VN05A0415^T (98.08 %), respectively. Strain J2-1^T had chemotaxonomic properties resembling members of the genus Streptomyces . ll-Diaminopimelic acid, glucose and ribose were detected in the whole-cell hydrolysate. Diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositolmannoside, unidentified aminolipid and five unidentified phospholipids were detected as the polar lipids. The major cellular fatty acids were C_16 : 0 iso, C_15 : 0 anteiso, C_15 : 0 iso, C_16 : 0, C_17 : 0 anteiso, C_14 : 0 iso and C_17 : 0 iso. Strain J2-2^T a showed similar cell composition to members of the genus Kineosporia . Both isomers of ll- and meso-diaminopimelic acid were detected in the peptidoglycan. Arabinose, galactose, madurose and xylose were observed in the whole-cell hydrolysate. The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside, phosphatidylcholine, an unidentified phospholipid and an unidentified glycolipid. The major cellular fatty acids were C_16 : 0, C_18 : 1 ω9c, C_18 : 0 10-methyl, tuberculostearic acid, C_18 : 0 and C_17 : 0. Both strains could be distinguished from their closely related type strains according to their phenotypic characteristics. Comparative genome analysis indicated the delineation of two novel species based on digital DNA–DNA hybridization and average nucleotide identity values, which were below 70 and 95 %, respectively. The names proposed are Streptomyces corallincola sp. nov. (J2-1^T=TBRC 13503^T=NBRC 115066^T) and Kineosporia corallincola sp. nov. (J2-2^T=TBRC 13504^T=NBRC 114885^T).

Two endophytic actinobacteria, designated as strains 7R015^T and 7R016^T, were isolated from the roots of Barleria lupulina collected in Thailand. The morphological characteristics and results of chemotaxonomic studies and 16S rRNA gene analysis indicated that both strains represented members of the genus Streptomyces . They contained ll-diaminopimelic acid in the peptidoglycan. Ribose and glucose were detected as the whole-cell sugars. MK-9(H₄), MK-9(H₆) and MK-9(H₈), were found as the membrane menaquinone. The predominant cellular fatty acids detected were iso-C_16 : 0 and anteiso-C_15 : 0. The genomes of both strains harboured biosynthetic gene clusters for melanin, terpene, lanthipeptide, polyketides, non-ribosomal peptide synthetase, siderophore and ectoine. The 16S rRNA gene sequence of 7R015^T showed the highest similarity to that of Streptomyces pseudovenezuelae DSM 40212^T (98.6 %), Streptomyces cyaneus NRRL B2296^T (98.6 %) and Streptomyces curacoi DSM 40107^T (98.6 %). Strain 7R016^T showed the highest 16S rRNA gene sequence similarity to Streptomyces gilvifuscus NBRC 110904^T (98.2 %), which is lower than the threshold value for 16S rRNA gene sequence similarity for differentiation at the species level (98.65 %). Comparative genome analysis revealed that the genomes of 7R015^T, 7R016^T and the closely related type strains had an average nucleotide identity (ANI) of less than 95 % and a digital DNA–DNA hybridisation (dDDH) of less than 70 %, the thresholds for species demarcation. On the basis of the results of the polyphasic study, strains 7R015^T and 7R016^T represent novel species of the genus Streptomyces and are named herein as Streptomyces cylindrosporus sp. nov. (=NBRC 115200^T = TBRC 14542^T) for strain 7R015^T and Streptomyces spinosisporus sp. nov. (=NBRC 115201^T = TBRC 14543^T) for strain 7R016^T.

Two actinobacteria, designated as strain LDG1-01T and LDG1-06T, were isolated from lichen samples collected in Thailand. Results of morphological characterization, chemotaxonomic studies and 16S rRNA gene analysis indicated that both strains were members of the genus Actinoplanes . MK-9(H4) was found as the major menaquinone. The major fatty acids were anteiso-C15 : 0, iso-C15 : 0, iso-C16 : 0 and anteiso-C17 : 0. Phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol were observed as the polar lipids, but differences in minor unidentified polar lipids were found between the strains. Results of comparative genome analysis based on average nucleotide identity and digital DNA–DNA hybridization calculations revealed that both strains showed values below 95 and 70 %, respectively, from each other and closely related Actinoplanes type strains. Based on data from this polyphasic study, strains LDG1-01T and LDG1-06T represent novel species of the genus Actinoplanes . The names proposed are Actinoplanes lichenicola sp. nov. (type strain, LDG1-01T (=JCM 33066T=TISTR 2982T) and Actinoplanes ovalisporus sp. nov. (type strain, LDG1-06T=JCM 33067T=TISTR 2983T).

Nile tilapia is one of the most consumed farmed fish in the world. The outbreak of pathogenic bacterial diseases causes high mortality rates and economic losses in Nile tilapia farming. Antibiotic administrations are commonly utilized to inhibit and prevent bacterial infections. However, antibiotics are expensive and cause serious concerns for antibiotic resistance in fish that can be potentially transferred to humans. As an alternative solution, probiotics can be used to prevent infection of pathogenic bacteria in fish. In this work, both bacteria and yeast were isolated from fish gastrointestinal tracts and their inhibitory activity against Nile tilapia pathogenic bacteria was evaluated, as well as other probiotic properties. In this study, 66 bacteria and 176 acid tolerant yeasts were isolated from fish gastrointestinal tracts. Of all isolated microorganisms, 39 bacterial and 15 yeast isolates with inhibitory effect against pathogens were then examined for their probiotic properties (acidic and bile salt resistance, adhesion potential, and biofilm formation), formation of antibacterial factor survival rate under simulated gastrointestinal fluid, and safety evaluation. AT8/5 bacterial isolate demonstrated probiotic properties and the highest inhibition against all 54 tested pathogens while YON3/2 yeast isolate outperformed the inhibitory effect among all yeast isolates. These two probiotic isolates were further identified by 16S rDNA and the D1/D2 domain of 26S rDNA sequence analysis for bacterial and yeast identification, respectively. AT8/5 and YON3/2 showed the highest similarity to Lactiplantibacillus argentoratensis and Candida tropicalis, respectively. This is the first report on isolated L. argentoratensis and C. tropicalis with antipathogenic bacteria of Nile tilapia properties. Collectively, AT8/5 and YON3/2 could be potentially used as promising alternatives to existing antibiotic methods to prevent pathogenic bacteria infection in Nile tilapia farming.