*2.1. Substrate*

Fish by-products (non-edible parts) of *Dicentrarchus labrax,* represented by the head, viscera, skin and bones, were provided by Acqua Azzurra S.p.a. (Pachino, Italy). Samples were collected directly at the farm, forwarded to the laboratory under refrigerated conditions, and stored at −20 ◦C until tests were performed. Lemon peel was provided by Simone Gatto S.r.l. (San Pier Niceto, Italy) and stored at −20 ◦C until use.
