**Sara B. Pereira 1,2,\*,**†**, Aureliana Sousa 1,3,**†**, Marina Santos 1,2,4, Marco Araújo 1,3, Filipa Serôdio 1,3, Pedro Granja 1,3,5 and Paula Tamagnini 1,2,6**


Received: 1 October 2019; Accepted: 12 November 2019; Published: 14 November 2019

**Abstract:** Biopolymers derived from polysaccharides are a sustainable and environmentally friendly alternative to the synthetic counterparts available in the market. Due to their distinctive properties, the cyanobacterial extracellular polymeric substances (EPS), mainly composed of heteropolysaccharides, emerge as a valid alternative to address several biotechnological and biomedical challenges. Nevertheless, biotechnological/biomedical applications based on cyanobacterial EPS have only recently started to emerge. For the successful exploitation of cyanobacterial EPS, it is important to strategically design the polymers, either by genetic engineering of the producing strains or by chemical modification of the polymers. This requires a better understanding of the EPS biosynthetic pathways and their relationship with central metabolism, as well as to exploit the available polymer functionalization chemistries. Considering all this, we provide an overview of the characteristics and biological activities of cyanobacterial EPS, discuss the challenges and opportunities to improve the amount and/or characteristics of the polymers, and report the most relevant advances on the use of cyanobacterial EPS as scaffolds, coatings, and vehicles for drug delivery.

**Keywords:** EPS-based biomaterials; cyanobacteria; designer biopolymers; extracellular polymeric substances (EPS), metabolic engineering; polymer functionalization
