Spirulina platensis is one of the most significant multicellular blue-green Cyanobacterium microalgae with a high protein content. The complex coacervation as an encapsulation technique allows the formation of proteins with improved functional properties and thermal stability. In this study, the effects of pH and Spirulina platensis protein concentrate (SPPC)—chitosan ratio on complex coacervation formation were examined in terms of ζ-potential, turbidity, visual observation and microscopic images. Based on the results, the strongest interaction between SPPC and chitosan occurred at pH of 5.5 and SPPC—chitosan ratio of 7.5:1 with a precipitation in the test tubes. Stable dispersions were obtained at a pH range of 2–4 for the SPPC—chitosan ratio of 7.5:1 inhibiting the precipitation which occurs at individual SPPC solutions at this pH range. Characteristic organic groups in the individual SPPC and chitosan solutions as well as the SPPC—chitosan coacervate formed at the optimal conditions were identified by using Fourier Transform Infrared (FT-IR) spectroscopy technique. Furthermore, thermal stability of the individual SPPC and chitosan solutions and the SPPC—chitosan coacervates were investigated using differential scanning calorimetry (DSC). The glass transition temperature and enthalpy were 209.5 °C and − 3.414 W/g for the complex coacervates and 180.5 °C and − 0.877 W/g for SPPC. It means that complex coacervation provided more thermally-stable SPPC in chitosan—SPPC coacervate than that of the individual SPPC. Our results might have important implications for the utilization of Spirulina platensis proteins especially for acidic beverage applications.

Ratios of 3:1 and 4:1 Fucus vesiculosus:zein (FV:Z) containing nanofibrous mats were designed for the first time by the electrospinning method. According to the results, electrical conductivity, surface tension, viscosity, and density are proportional to each other. Scanning electron microscopy (SEM) images depicted morphology, revealing the presence of homogeneous nanostructures. Changing the polymer ratios altered the fiber diameter, specific surface area, pore volume, and pore size. Average values of hydroxycinnamic (21.5 μgmg^–1), quercetin (19.8 μgmg^–1), and caffeic (16.23 μgmg^–1) were determined to be the highest phenolic compounds in the HPLC chromatogram, serving as an important source of bioactive ingredients for food applications. Total IC50 values of FV:Z 3:1 and FV:Z 4:1 mats were 46.37 μgml^–1 and 46.90 μgml^–1, respectively. Total phenolic content (TPC) is also presented at higher levels in all of the ABTS and DPPH assays. Determination of the H atom in the −OH group and the carbonyl group of a carboxylic acid group of phenolic acid in the FTIR spectrum was consistent with the ABTS and DPPH results. In the FTIR spectra for nanofibrous mats, vibrations shifted toward smaller wavenumbers with stronger ionic interaction compared to the FV extract. Slightly shifted and increased peaks were observed in the spectra, confirming successful interaction between Fucus and zein. Functional groups (NH₂, COOH, and OH) allow intermolecular interactions such as H bonding. π–π stacking, π alkyly, and sulfur-containing products are detected. TGA and DSC results showed that the thermal stability of nanoencapsulated FV bioactive compounds strengthened at higher temperatures. Differences in XRD crystal patterns, such as changes in the intensities of diffraction peaks, were also recognized between samples. Overall, stability and bioactivity improved with the formation of inter/intramolecular associations. Results indicated that nanofibrous mats have potential in the nanoencapsulation and delivery of bioactives.

This study investigated the root uptake and adsorption kinetics of Kiperin dihydrolyzed collagen (KDHC), an organic nitrogen source rich in amino acids and low-molecular-weight peptides, in radish (Raphanus sativus L.) seedlings grown in perlite. KDHC was applied at 0.1, 1.0, and 10 g L⁻¹ to 7-day-old seedlings. Directly measured solution depletion and tissue accumulation were distinguished from processes inferred from model fits, such as apoplastic adsorption and transport between organs. Amino acid depletion from the root medium increased with the applied concentration, and the Freundlich, Langmuir, Dubinin–Radushkevich, and Flory–Huggins isotherm models described amino acid binding to the root surface. Depletion from the root medium followed pseudo-first-order kinetics (R² = 0.94–0.99), reflecting rapid apoplastic surface adsorption within 60 min. In an ex vivo leaf disk assay, cellular accumulation in leaf tissue followed the pseudo-second-order model (R² = 0.9881), suggesting a carrier-mediated mechanism. Differences among amino acids were interpreted in relation to their charge states at pH 5.8 and their molecular size. Root-to-shoot translocation was not traced directly and should be confirmed using isotope-labelled amino acids. These findings indicate that KDHC-derived amino acids are readily available to radish roots and may serve as an organic nitrogen source.