**Abstract**

In this chapter, the authors will show different proposals of magnetic bio-derivatives and its applicability in biotechnology. The historical context of immobilized enzymes, as well as highlighting the main advantages and disadvantages of each, will be mentioned. Besides, iron oxides and composite materials will be presented as support for biomolecules immobilization. Composites are effortlessly prepared including many materials capable of providing advantages to the magnetic derivatives. Enzymes covalently linked to these magnetic particles combine their catalytic properties with reaction specificity, reusability, and possible reactor construction. In addition, proteins can also be purified by these magnetic composites containing specific ligands allowing reactors and reuses too. Some characterization techniques used to study the magnetic material and derivative immobilized will be described as well. Altogether, an engaging presentation about the interesting features of magnetic bio-derivatives will highlight their uses in biotechnology field as well as in others.

**Keywords:** iron oxides, composite, enzyme, protein, immobilization, purification
