Currently, there is not a single industrial-scale syngas fermentation-to-biofuel plant. Gas — to-liquid mass transfer is still considered as the major bottleneck for the commercialization of syngas fermentation technology. Keegan (2008) reported the construction of 40,000 gal per year pilot plant and a 40- to 100-million gal per year commercial-scale syngas fermentation facility. Kundiyana et al. (2010) reported a successful operation of a 100-L pilot scale syngas fermentation facility. Regardless of the recent developments in reactor designs, process optimizations, and microbial catalysts selection, the ethanol concentration from syngas fermentation is still just under 30 g/L. This leads to a high cost of ethanol recovery. For cost-effective ethanol recovery, its concentration should be around 15% (v/v). Therefore, in order to reduce the recovery cost, thus improving the overall economy of the process, industrial-scale syngas fermentation should focus on achieving higher ethanol concentration. This requires significant research and development in process microbiology.