The neoagaro-oligosaccharides, degraded from agarose by agarases, are important natural substances with many bioactivities. In this study, a novel agarase gene, agaW1540, from the genome of a deep-sea bacterium Shewanella sp. WPAGA9, was expressed, and the recombinant AgaW1540 (rAgaW1540) displayed the maximum activity under the optimal pH and temperature of 7.0 and 35 °C, respectively. rAgaW1540 retained 85.4% of its maximum activity at 0 °C and retained more than 92% of its maximum activity at the temperature range of 20–40 °C and the pH range of 4.0–9.0, respectively, indicating its extensive working temperature and pH values. The activity of rAgaW1540 was dramatically suppressed by Cu²⁺ and Zn²⁺, whereas Fe²⁺ displayed an intensification of enzymatic activity. The K_m and V_max of rAgaW1540 for agarose degradation were 15.7 mg/mL and 23.4 U/mg, respectively. rAgaW1540 retained 94.7%, 97.9%, and 42.4% of its maximum activity after incubation at 20 °C, 25 °C, and 30 °C for 60 min, respectively. Thin-layer chromatography and ion chromatography analyses verified that rAgaW1540 is an endo-acting β-agarase that degrades agarose into neoagarotetraose and neoagarohexaose as the main products. The wide variety of working conditions and stable activity at room temperatures make rAgaW1540an appropriate bio-tool for further industrial production of neoagaro-oligosaccharides.

This study investigated species-specific physiological and redox responses of two coral symbiotic dinoflagellates, Cladocopium sp. and Durusdinium sp., to green-synthesized nano-selenium (SeNP) gradients, with implications for eco-friendly marine antifouling. Growth, photosynthetic pigments, antioxidant enzymes (SOD, POD, CAT), lipid peroxidation (MDA), and osmo-protectants were assessed to elucidate mechanisms. Both species exhibited a biphasic (hormetic) response, with stimulation at low concentrations and inhibition at high levels. At 50–100 mg L⁻¹, Cladocopium sp. showed enhanced growth, pigments, antioxidant activity, and osmotic regulation, with reduced oxidative stress, indicating improved redox homeostasis. In contrast, ≥150 mg L⁻¹ disrupted redox balance and suppressed growth. Durusdinium sp. displayed slower growth but maintained stable pigments, consistent antioxidant activity, and low MDA, reflecting a tolerance-oriented strategy. Overall, SeNPs synergistically regulate antioxidant systems and osmotic homeostasis to balance the intracellular redox status of symbiotic dinoflagellates, indicating their potential as antioxidant agents to improve the growth performance of symbiotic dinoflagellates in coral nursery cultivation.

Chromium (Cr) contamination poses a serious threat to agricultural productivity and food safety, yet effective strategies for mitigating Cr toxicity under practical cultivation conditions remain limited. In this study, green-synthesized selenium nanoparticles (SeNPs), prepared from banana peel extract (average particle size: 112.9 nm), were evaluated against conventional sodium selenite (Na₂SeO₃) for alleviating Cr(VI) toxicity in Ipomoea aquatica Forssk. grown in a dynamic cyclic hydroponic system. Plants were exposed to 20 mg L⁻¹ Cr(VI) and treated with SeNPs or Na₂SeO₃ at 1 and 10 mg L⁻¹, respectively, for a duration of one week. Green-synthesized SeNPs exhibited excellent colloidal stability (zeta potential: −35.5 mV) and an amorphous spherical morphology. Relative to the Cr-only treatment, 10 mg L⁻¹ SeNPs almost completely restored plant biomass and root growth, decreased shoot Cr accumulation by 62.2%, and recovered total chlorophyll content to 94.8% of the control level. By comparison, 10 mg L⁻¹ Na₂SeO₃ restored total chlorophyll to 74.2% of the control and reduced shoot Cr accumulation by 50.6%. SeNPs also elicited a stronger antioxidant response, markedly increasing SOD, POD, and CAT activities while significantly lowering H₂O₂, MDA, and proline levels, demonstrating a greater capacity than selenite to alleviate Cr-induced oxidative damage. SeNPs also restored the uptake of essential mineral nutrients (N, P, K, Ca, and Mg), improved soluble sugar and protein contents, and promoted selenium biofortification in edible shoots. Although both selenium forms alleviated Cr-induced growth inhibition and oxidative damage, SeNPs consistently outperformed Na₂SeO₃ owing to their higher bioavailability and sustained physiological activity. Overall, this study demonstrates that green-synthesized SeNPs provide an efficient and sustainable strategy for reducing Cr accumulation while simultaneously improving crop growth, antioxidant capacity, and nutritional quality under agriculturally relevant hydroponic conditions, highlighting their potential for safer food production and agricultural waste valorization.