Characterization of major algal species and their prebiotic potential

In animal health, the need for a sustainable system that limits the phenomenon of antibiotic resistance is becoming increasingly evident. In this context, functional foods or ingredients are gaining ground and are also being researched as waste products from the supply chain. Among these, algal biomass is particularly rich in polysaccharides, which could potentially be exploited as prebiotic functional ingredients for both human and animal health applications. To this end, this study aimed to determine the potential prebiotic role of two algae species employed in animal nutrition, Ascophyllum nodosum and Lithothamnium calcareum. Initially, a metabolomic profile characterization was performed by LC-QTOF-MS system, in order to assess the content of bioactive compounds of the two algal species. Therefore, the effect of A. nodosum and L. calcareum extracts and their combination was evaluated in vitro on the growth of Lactobacillus plantaurum. The antioxidant capacity was determined by the ABTS Radical Cation Decolorization Assay, and the total antioxidant capacity was expressed as the percentage of inhibition of radical scavenging (PI%). The antimicrobial effect of L. plantaurum cultured with algal extracts against porcine O138 E. coli was evaluated following the microdilution bacterial growth method. The metabolomic characterization confirms the functional potential of algal extract, showing a high amount of all the bioactive compounds including polysaccharides. Thanks to the presence of these compounds algal extracts are also able to improve the growth of Lactobacillus plantaurum in vitro. In fact, after 8hrs of incubation both algal extracts improved L. plantarum growth, increasing it by about 30%. Furthermore, co-culture of L. plantarum with the extract of the algal combination allowed for increased growth as early as 6hrs of incubation. Moreover, the presence of different bioactive compounds in the algal extracts, allowed an improvement in both antioxidant and antimicrobial capacity of L. plantaurum. The results obtained from this study disclose that the extracts of A. nodosum and L. calcareum can be considered valid prebiotics in order to enhance the functional properties of L. plantaurum. Further in vitro studies will be conducted to complete the knowledge about the employment of the algal extract as prebiotic, in order to subsequently evaluate their effect in vivo