Three differently immobilized preparations of an enzyme extract from Candida boidinii containing a NAD(+)-dependent formate dehydrogenase (CbFDH) were prepared by encapsulation using calcium alginate (CbFDH-Alg) or polyvinyl alcohol (CbFDH-PVA) or by adsorption on montmorillonite K 10 (CbFDH-Mont). All FDH preparations were characterized in terms of both oxidation and reduction activities. For the formic oxidation activity, all immobilized FDHs had 100% activity at pH 8.0 and 50 degrees C, as the soluble enzyme. Among the immobilized biocatalyst, only CbFDH-PVA showed activity in the reduction of hydrogen carbonate and had 100% activity at pH 6.0 and 40 degrees C, as the soluble enzyme. The half-life values of immobilized enzymes increased by at least 3.1-folds compared to the soluble enzyme. Formic acid was produced from HCO3- as a source of carbon dioxide using soluble CbFDH and CbFDH-PVA and the formic acid yields were determined as 80 and 92%, respectively for soluble CbFDH and CbFDH-PVA after 240 min reaction. CbFDH-Alg, CbFDH-PVA and CbFDH-Mont retained 40.1, 49.8 and 26.1% of their initial activities after 10 reuses in formate oxidation reaction. The remaining reduction activity of CbFDH-PVA was 30% after 10 reuses. These results show the CbFDH immobilization following different protocols strongly alter their oxidation/reduction activities.