Techniques of microencapsulation and fabrication of core-shell structures are widely used in drug delivery and in the pharmaceutical and cosmetic industry for the encapsulation of aromas and solvents. Their use for environmental purposes has been less exploited. In this presentation, we report the use of natural polymers in conjunction with magnetic nanoparticles for the development of multifunctional core-shell structures with immobilized enzymes for environmental applications including remediation and sensing of phenolics, pesticides and certain endocrine disrupting chemicals. The method is based on the combined use of enzymatic oxidation of the substrate and subsequent adsorption of the reaction product onto a specifically tailored core material. Thus, both enzymatic and chemical reactions are performed in the interior of a core/shell structure with multifunctional properties including biocatalytic and magnetic capabilities for easy removal and handling. These multifunctional structures are stable to ambient conditions and are environmentally benign. We will discuss the fabrication, optimization, and analytical performance of these systems for the sensing and remediation of environmental pollutants.