NAD+-dependent formate dehydrogenases (EC 1.2.1.2, FDH) is the enzyme which oxidizes formate ion with coupled reduction of nicotineamide adeninine dincleotide (NAD+ and NADH oxidized and reduced forms, respectively). FDH possesses unique substrate specificity towards to formate-ion and can be used in biosensors for selective determination of NAD+ or NADH in complex mixtures including human fluids. There are many different methods for enzyme immobilization on the electrode surface. Most of them do not provide enough high surface density and long operational stability. In this laboratory we have developed method to produce LB-films of NAD+-dependent formate dehydrogenase from bacterium Pseudomonas sp.101 (PseFDH) on buffer-air phase border. Varying experimental conditions different enzyme orientation in monolayer can be achieved. Hydrophobisation of PseFDH by site directed mutagenesis improved efficiency of LB-films preparation. We also developed procedure to transfer monolayers from air-buffer phase border to surface of silica electrode. Repeat of procedure resulted in up to 11 monolayers of the enzyme on electrode surface. Immobilization of the PseFDH as monolayers on silica plates increased the enzyme thermal stability by 25-30 degree. Biosensors prepared were used to develop method for NAD+ detection in solutions.