Sea Bass Side Streams Valorization Assisted by Ultrasound. LC-MS/MS-IT Determination of Mycotoxins and Evaluation of Protein Yield, Molecular Size Distribution and Antioxidant Recovery

Sea bass side streams obtained from the fish industry can be a good source of nutrients such as high-quality protein, lipids, and antioxidants. In this context, it is interesting to develop innovative approaches to extract the added-value compounds from fish side streams. In this study, a strategy to obtain valuable compounds and to minimize the presence of toxins from fish side streams assisted by ultrasound technology is presented. For this purpose, ultrasound-assisted extraction (UAE) conditions have been optimized based on a response surface methodology (RSM) with the dependent variables: time (0.5–30 min), pH (5.5–8.5), and temperature (20–50 °C). After the treatment, protein extraction and antioxidant activity were evaluated in the extracts obtained from sea bass side streams using some spectrophotometric and fluorometric methods. Furthermore, mycotoxin presence was evaluated by LC-MS/MS-QTRAP. The results obtained revealed a high recovery percentage of proteins and antioxidant activity in the UAE extracts, especially those obtained from viscera, when the time and temperature increased to 30 min and 50 °C. Furthermore, none of the analyzed mycotoxins were detected in the sea bass side streams extracts under the studied variables. The experimental values obtained were close to the expected values, confirming the validity of the model employed to establish the optimal UAE conditions.

Generation of lignin polymer models via dehydrogenative polymerization of coniferyl alcohol and syringyl alcohol via several plant peroxidases involved in lignification and analysis of the resulting DHPs by MALDI-TOF analysis

The mechanism of lignin dehydrogenative polymerization (DHP), made by means of horseradish peroxidase (HRP), was studied in comparison with other plant peroxidases. Interestingly, HRP is efficient for guaiacyl type polymer formation (G-DHPs), but is not efficient in the case of syringyl type DHPs (S-DHPs). It was previously demonstrated that lignification-relatedArabidopsisthalianaperoxidases, AtPrx2, AtPrx25 and AtPrx71, and cationic cell-wall-bound peroxidase (CWPO-C) fromPopulus albaare successful to oxidize syringyl- and guaiacyl-type monomers and larger lignin-like molecules. This is the reason why in the present study the DHP formation by means of these recombinant peroxidases was tested, and all these enzymes were successful for formation of both G-DHP and S-DHP in acceptable yields. CWPO-C led to S-DHP molecular size distribution similar to that of isolated lignins.