Chitosan and alginate are two carbohydrate polymers derived primarily from marine organisms.  In addition to a polysaccharide backbone, chitosan and alginate are polycationic and polyanionic, respectively. Their hydration, chelation and ionic-binding properties have long been used in pharmaceutical formulations and recently, have been extended to biotechnology applications, including chromatography, cell and enzyme immobilization, gene transfection and related biotechnology processes. This mini-review will address the chemical composition, sources, synthetic modification and applications of these polymers in biotechnology.