Ethanol and other liquid products are produced by contacting syngas components such as CO or a mixture of CO2 and H2 with a surface of a membrane under anaerobic conditions and transferring these components into contact with a biofilm on the opposite side of the membrane. These steps provide a stable system for producing liquid products such as ethanol, butanol and other chemicals. The gas fed on the membrane's gas contact side transports through the membrane to form a biofilm of anaerobic microorganisms that converted the syngas to desired liquid products. The system can sustain production with a variety of microorganisms and membrane configurations.