A bioreactor should provide a controlled environment to enhance cell growth, substrate conversion and productivity of the biological process, and minimize the overall cost of production of desired products . Continuous stirred tank reactors, bubble columns, packed columns, air-lift, trickle beds and hollow fiber reactors are some of the bioreactor configurations studied for alcohol production using syngas fermentation. Further, these reactors can be operated in different fermentation modes such as batch, fed-batch, continuous with and without cell recycle used two STRs in series and reported a 30 fold increase in ethanol productivity using C. ljungdahlii. showed that the use of a microsparger in a STR for production of acetate, ethanol and butyrate by Butyribacterium methylotrophicum increased the mass transfer by six times with 50% of the flow rate used without a microsparger. The highest ethanol concentration of 48 g/L was produced in a continuous syngas fermentation in a CSTR with cell recycle . A list of reactors used for syngas fermentation, syngas composition, ethanol yield and productivity is shown in Table 1.