*Article* **Potential of Exopolysaccharide from** *Porphyridium marinum* **to Contend with Bacterial Proliferation, Biofilm Formation, and Breast Cancer**

**Nesrine Gargouch 1,2, Fatma Elleuch 3,4, Ines Karkouch 5, Olfa Tabbene 5, Chantal Pichon 3, Christine Gardarin 1, Christophe Rihouey 6, Luc Picton 6, Slim Abdelkafi 4, Imen Fendri 2 and Céline Laroche 1,\***



 **\*** Correspondence:celine.laroche@uca.fr;Tel.:+33-473-40-74-19

**Abstract:** Exopolysaccharide (EPS) from marine microalgae are promising sources of a new generation of drugs. However, lot of them remain to be discovered and tested. In this study, EPS produced by *Porphyridium marinum* and its oligomers prepared by High Pressure Homogenizer have been tested for different biological activities, i.e., antibacterial, anti-fungal and antibiofilm activities on *Candida albicans*, as well as for their effects on the viability of murine breast cancer cells. Results have shown that all EPS samples present some biological activity. For antibacterial and antibiofilm activities, the native EPS exhibited a better efficiency with Minimum Inhibitory Concentration (MIC) from 62.5 μg/mL to 1000 μg/mL depending on the bacterial strain. For *Candida albicans*, the biofilm formation was reduced by about 90% by using only a 31.3 μg/mL concentration. Concerning breast cancer cells, lower molar masses fractions appeared to be more efficient, with a reduction of viability of up to 55%. Finally, analyses of polymers composition and viscosity measurements were conducted on all samples, in order to propose hypotheses involving the activities caused by the intrinsic properties of polymers.

**Keywords:** *Porphyridium marinum*; exopolysaccharide; high pressure homogenizer; antibacterial activity; anti-biofilm activity; anti-cancer activity
