Use of hydrolysates from yellowfin tuna Thunnus albacares fisheries by-product as a nitrogen source for bacteria growth media

Hydrolysates of tuna head, using commercial enzymes Alcalase® (Alc) and Protamex™ (Prot), were tested as growthmedia for the bacterial strains of Pseudomonas putida, Pseudomonas aeruginosa, Streptococcus faecium, Listeriamonocytogenes, Bacillus subtilis, Bacillus licheniformis and Micrococcus lysodeikticus, as an alternative to commonlyused complex sources (peptones and/or extracts). Peptones from the enzymatic hydrolysis by Alcalase and Protamexwere used instead of standard peptones used in commercial media. All bacteria were cultured on traditional standardmedia as controls, and their growth was compared to ones grown on experimental media containing Alc- and Protpeptoneinstead of the standard peptone. Peptones produced by Alcalase and Protamex had obtained 34 and 19% degreeof hydrolysis, respectively. The results showed that both the Alcalase and Protamex peptones were more effective atpromoting bacterial growth than the standards used in traditional media, while the peptone from Alcalase, with a higherpercent of hydrolysis, was more effective than the peptone from Protamex, also in terms of biomass production, Thusthe choice of the proteolytic enzymes used to produce the fish hydrolysates had a considerable impact on theperformance of the resulting hydrolysate.