Nitric oxide (NO), a major nitrogen oxide component in fossil fuel flue gas, was removed by the green alga Dunaliella tertiolecta cultivated in bubble column and airlift reactors. As NO removal was enhanced by increasing the dissolution of NO in water, increasing the gas-liquid contact area and time was deemed as an effective method for improving NO removal. The highest level of NO removal, 96%, was achieved with a counter-flow type airlift reactor when 100 ppm NO was aerated with smaller bubbles.