A novel hox-shaped shake flask with membrane Biters fitted in its upper sides was developed for efficient gas exchange. During rotation, the liquid flow inside the flask is broken up at tile four angles of the flask, while membrane Biters ire opposite sides serve alternately as gas inlet and outlet ports, depending on the direction in which the flask is moving. Consequently, the oxygen transfer coefficients both across the gas-liquid interface and through the membrane filters are snore than ten times higher than those in an Erlenmeyer flask with a cotton plug. The volumetric oxygen transfer coefficient, volatilization rate constant, and cultivation performance of representative strains of microorganisms were used to evaluate the gas exchange capacity of the newly developed shake flask. It was confirmed that the gas exchange capacity of the flask was the same as that of a jar fermentor.