**5. Conclusions**

The present study demonstrated the biological activity of different molar masses exopolysaccharides from *Porphyridium marinum*. Interestingly, our findings clearly revealed the potentiality of native exopolysaccharide EPS-0C to inhibit the proliferation of Gram (+) and Gram ( −) bacteria, as well as the formation of biofilm of *Candida albicans* at low concentration. However, the low molar masses exopolysaccharides EPS-2C and EPS-5C were found to be more effective for antiproliferative activity against breast cancer cells. Depending on the biological activity tested, this study also disclosed that these biological activities could be due to their molar masses, their viscosity as well as their composition (probably their content in sulfate and uronic acids). Thus, this study provides strong arguments to consider exopolysaccharides from *Porphyridium marinum* as a natural source of antibacterial, antibiofilm and anticancer products that are useful in pharmaceutical formulations and food industries as a natural preservative. Nevertheless, this study constitutes a first step to evaluate the potential of EPS from *P. marinum* in a drug development approach.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/1660-339 7/19/2/66/s1, Figure S1: HPAEC chromatograms of native (a: EPS-0C) and depolymerized EPS (b: EPS-2C, c: EPS-5C).

**Author Contributions:** Conceptualization: N.G., I.F. and C.L.; Investigation: N.G., I.K., F.E., C.G. and C.R.; Supervision: C.P., S.A., O.T., I.F. and C.L.; Validation: I.F. and C.L.; Writing—original draft: N.G. and C.L.; Writing—review & editing: I.K., C.R., L.P., I.F., N.G. and C.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data is contained within the article or Supplementary Materials.

**Conflicts of Interest:** The authors declare no conflict of interest.
