# Marine microalgae Biomolecules and Their Adhesion Capacity to _Salmonella enterica_ sv. Typhimurium
## 1 Introduction  
Microalgae are photosynthetic microorganisms capable of producing a wide variety of biomolecules in accordance with the division or class to which they belong. The large biodiversity encompasses about 200,000-800,000 species, of which only 50,000 have been taxonomically defined and over 15,000 novel compounds have so far been associated with algae biomass, including carotenoids, sterols, phylochiloproteins, phytotoxins, and polysaccharides [1; 2; 3]. Phylum Haptophyta comprises two classes, Coccolithophyceaeae and Pavlovophyceae [4], where the latter includes the two marine species under study, _Pavlova lutheri_ and _Pavlova gyrans_. Since they can be easily grown, quickly ingested and digested, and exhibit a high nutritional value, these species, as well as some other microalgae, are widely used as raw material in the aquaculture of fish, mollusks, and crustaceans [5; 6; 7]. All these characteristics have also aroused the interest of the biotechnology sector for the potential use of these microorganisms in nutritional and pharmaceutical bioproducts [8].  
Polysaccharides and oligosaccharidesarchides from different microalgal sources have widely diverse chemical structures and are known to have multiple biological activities [9; 10]. Numerous investigations have suggested that some types of carbohydrates can avoid enteric infections by inhibiting adhesion of enteropathogens to the host tissue [11; 12; 13; 14; 15]. Adhesion is the first step in a bacterial infection process and it is mediated via adhesins expressed by bacteria that recognize and adhere to ligand-like carbohydrates located on the surface of host epithelial cells [16]. Thus, carbohydrates can act as analog receptors, mimicking the host receptors and participating in binding with specific bacterial adhesins. Therefore, anti-adherence therapies act to reduce infections and diseases, as well as the risk of transmission via the food chain. In addition, its application acts as an alternative to the inappropriate and excessive use of antibiotics with the added benefit of reducing selective pressure since pathogens are not killed, they are only impeded from attaching to host cells [17].  
Commercial products with anti-adhesive properties that are derived from yeast cell walls and contain mannose have been sold worldwide for a long time and employed in animal feed to bind pathogens and prevent bacterial adhesion [18; 19]. Few studies examining the anti-adhesive properties of polysaccharides derived from microalgae are available in the literature. [PERSON] and [PERSON] [20] reported that sulfated exopolysaccharides from _Tetraselmis_ sp., _Neochloris oleoabundans_, and _Phaeodactylum tricornutum_ caused a 50% inhibition of adhesion of _Helicobacter pylori_ to HeLa S3 cells. According to [PERSON] et al. [21], polysaccharides obtained from _Spirulina_ and _Chlorella_ were capable of preventing _H. pylori_ from binding to gastric mucin. Thus, the present study aimed to obtain and characterize aqueous and alkaline extracts from microalgae _P. lutheri_ and _P. gyrans_ and evaluate, using an in vitro assay, the ability of these extracts to adhere to enterobacteria _Salmonella enterica_ sv. Typhimurium.