Integrated technology for processing salmonid fish milt to obtain biologically active DNA and hyaluronidase

Introduction: Fish milt is currently used predominantly as a culinary product, despite containing numerous biologically active compounds with high value-added potential, including nucleoproteins, enzymes, and proteins. Its integrated processing creates an opportunity to recover biologically valuable compounds, including DNA and hyaluronidase, within a single technological cycle. Objective: To develop an integrated technology for the processing of fish milt with the sequential recovery of DNA and hyaluronidase while preserving their target properties. Materials and Methods: Frozen fish milt was mechanically homogenized and extracted at reduced temperature with acetic acid using a raw material-to-extractant ratio of 1:2. Following centrifugation, the soluble fraction containing hyaluronidase was clarified and concentrated by ultrafiltration. The precipitate containing the DNA–protein complex was hydrolyzed with trypsin at a water-to-precipitate-to-trypsin ratio of 2:1:0.3 and subsequently centrifuged to isolate the DNA fraction. Hyaluronidase activity was determined using a pharmacopeial method. The enzyme-containing fraction was additionally characterized by Fourier-transform infrared spectroscopy. DNA quality was assessed by spectrophotometry; residual protein in the DNA fraction was quantified using the micro-biuret method, and the preparation was additionally characterized by infrared spectroscopy. The yields of DNA and the hyaluronidase-containing fraction were determined using a rapid drying method at 170 °C. Results: The developed technological scheme enabled recovery of the target products from a single raw material. The DNA yield was 11.3% of the initial raw material mass. The final fraction contained 60–65% DNA, and the A260/A280 ratio ranged from 1.80 to 1.90, indicating relatively high purity. The yield of the hyaluronidase-containing fraction was 4.8% of the initial raw material mass on a dry-weight basis. Ultrafiltration increased specific activity of hyaluronidase-containing fraction 1.77-fold, from 1375 to 2437 IU/mg. Fourier-transform infrared spectroscopy confirmed the proteinaceous nature of the enzyme-containing preparation. Novelty of the Study: This study proposes an integrated technological scheme for fish milt processing that enables the sequential recovery of a hyaluronidase-containing fraction and a DNA fraction from a single raw material. The use of ultrafiltration as a concentration step increases enzyme activity without requiring expensive chromatographic purification, thereby improving the practical feasibility of the process. Conclusions: The proposed technology enables rational utilization of fish milt as a secondary biological raw material and allows recovery of biologically valuable DNA and a hyaluronidase-containing fraction within a single production cycle. The developed approach is technologically feasible and promising for further application in biotechnology, food processing, and pharmaceutical production. Keywords: fish milt, DNA, hyaluronidase, ultrafiltration, integrated processing, bioactive compounds.