Postbiotics are metabolic by-products from microorganisms that provide
health benefits to the host. Their secretion can be influenced by various
conditions affecting bacterial metabolism. This study presents a novel ap-
proach for producing potential postbiotics, specifically extracellular products
(ECPs), from the probiotic strain Shewanella putrefaciens SpPdp11, grown
under different culture conditions. These conditions include aquafeed media,
with partial or total microalgae/cyanobacteria replacement as the microbial
substrate, as well as variations in temperature and growth phase. The use of
microalgae/cyanobacteria as substrates may represent a valuable strategy
for generating novel postbiotics with unique properties. The ECPs assessed
were evaluated for their in vitro cytotoxic, hydrolytic and antimicrobial ac-
tivities. Three conditions (ECPs derived from aquafeed media with partial
(FM2324 and FM1548) or total (M2324) microalgae/cyanobacteria replace-
ment) were non- cytotoxic to various fish cell lines and hydrolysed key nutri-
tional compounds (casein, lipids, amylase and gelatin). Proteomic analysis
of these ECP conditions revealed common structural and regulatory DNA-
associated proteins, while differentially expressed proteins were associated
with amino acid metabolism and antioxidant system (FM2324 and FM1548)
and chemotaxis system (M2324). The results highlight the potential of the
selected postbiotics as feed additives for future in vivo studies, aligning with
sustainable development for aquaculture.
