Enzyme are specific biocatalysts to perform and regulate processes especially, chemicals, pharmaceutical and food industries. However, the use of enzymes is handicapped by their low operational stability, their difficult recovery and reuse. But these obstacles could generally be overcome by immobilization and stabilization. The objective of this thesis is focused on the development of enzyme stabilizing system using nano/micro-sized hybrid materials to overcome these disadvantages by enhancing storage and operational stability, as well as facilitate simple separation and easy recovery for reuse. Furthermore, stabilized enzyme system is applied to bioconversion in practical application,. The first part of this thesis describes development and characterization of stable and magnetically separable enzyme stabilizing system, comprising of organic-inorganic hybrid microspheres. The hybrid microspheres was fabricated by electrospinning process and modified sol-gel methods, and well characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX). The immobilized enzyme using hybrid microspheres have an advantageous feature of magnetic separability and was found to be highly stable and active during more than 100 days stored and can be reused more than 15 times. Furthermore, the magnet-based separation was also found to be successful for the repeated usages of recycled microspheres. The second part of this thesis is about the development and characterization of QDs-nanofibers by electrospinning. Uniformly distributed QDs within the polymer matrix of nanofibers induced high degree of compactness and shape rigidity in the nanofibers and also showed efficient enzyme immobilization. Therefore, the patch type QDs-nanofibers with immobilized enzyme can be considered as attractive novel carrier for various applications to increase their stability. The third part of the thesis is a study for stabilized enzyme to apply the synthetic reaction in organic solvent. Magnetically-separable mesocellular silica (Mag-MSU-F), with larger mesocellular pores of 38 nm connected with smaller window mesopores of 18 nm and deposited magnetic nanoparticles, were used for the immobilization and stabilization of subtilisin Carlsberg (SC) from Bacillus licheniformis in the form of nanoscale enzyme reactors (NERs). As a result, NER-SC was stabilized in the buffer condition. Stable NER-SC was freeze-dried and successfully used for the transesterification of N-acetyl-L-phenylalanine ethyl ester (APEE) with n-propanol in isooctane. Facile magnetic separation also helped to realize the repeated uses of stable NER-SC. This is the first demonstration for the uses of stable and magnetically-separable NERs in organic solvents, which will create a great potential for various synthetic reactions such as the biodiesel production. The last part of this thesis is about the development and characterization of amorphous calcium phosphate nanocomposites (ACP-NCs) by biomineralization. Enzyme-modulated formation of biomineralized ACP-NCs shows spherical, high surface areas (163 m2 g-1 or 0.37 cm3 g-1) and narrow pore size distribution (6 ~ 10 nm) with size range of about 100 nm. showing high enzyme loading capacity upto ~70%. Therefore, ACP-NPs with immobilized enzyme can be considered as attractive novel carrier for various applications to increase their stability, and furthermore, ACP can be clue for biomineralization using enzymes.