In this study, the benzaldehyde lyase (BAL, EC 4.1.2.38) production in E. coli BL21 (DE3) pLySs as intracellular and in Bacillus species as extracellular were investigated, and comparison of the production capacity of the enzyme in the developed recombinant microorganisms were compared. For this purpose, firstly, PCR amplified bal gene was cloned into pRSETA vector which is under the control of strong T7 promoter and expressed in E. coli BL21 (DE3) pLysS strain. With developed recombinant E. coli BL21 (DE3) pLySs cells, the effect of bioprocess parameters was systematically investigated. Among the investigated media, the highest cell concentration and benzaldehyde lyase activity were obtained as 2.0 kg m-3 and 1060 U cm-3, respectively, in the medium containing 20.0 kg m-3 glucose, 11.8 kg m-3 (NH4)2HPO4 and the salt solution. Thereafter, oxygen transfer effects on benzaldehyde lyase production were investigated at air inlet v rate of QO/VR = 0.5 vvm, and agitation rates of N=500 and 750 min-1 and at QO/VR = 0.7 vvm, N=750 min-1 in pilot scale bioreactor and the highest cell concentration and volumetric BAL activity were found as 1.7 kg m-3 and 990 U cm-3, respectively, at 0.5 vvm, 750 min-1 condition. Next, the signal DNA sequence of serine alkaline protease (SAP) from B. licheniformis DSM 1969 chromosomal DNA (pre-subC) was fused in front of the bal by using PCR-based gene splicing by overlap extension (SOE) method. The fusion product of hybrid gene first cloned into pUC19 plasmid, thereafter sub-cloned into pBR374 shuttle vector and recombinant plasmid was transferred into various Bacillus species. However, no extracellular production of benzaldehyde lyase was observed in none of the developed recombinant Bacillus species, probably because of ineffective secretion system, inefficient folding of heterologous protein, degradation of enzyme due to proteolytic activity or high inactivation rate of the enzyme.