Industrial Application. Engaging in ecological questions entails seeking novel enzymes with selected functions. Our emphasize lies on [NiFe] hydrogenases (catalyzing H2 ↔ 2H+ + 2e) and carbon monoxide dehydrogenases (CODH) (catalyzing CO + H2O + A ↔ CO2 + AH2). If immobilized on surfaces hydrogenases can be useful for (i) production of hydrogen as an energy carrier (fuel storage in electrochemical cell) and (ii) oxidation of hydrogen as an energy source (fuel cell). CODH can produce carbon monoxide, which has a significant fuel value and is also used as feedstock for different synthetic reactions. Aside CO2 concentrations can be reduced in flue and other waste gases.