The present invention provides an apparatus for dissolving a gas in a liquid, the apparatus comprising (a) a closed vessel containing a liquid at a predetermined level, (b) a contactor module at least partially immersed in the liquid having (1) a gas supply channel to the bore side of the fibers, (2) a liquid supply channel to the shell side of the fibers, and (3) an exit port for transport of a gas-containing liquid, and (c) the remaining space in the closed vessel being occupied by a pressurized gas. The liquid prepared in the apparatus of the present invention containing a dissolved gas, is used to prepare beverages, such as coffee, tea, soda, chocolate and the like, whether hot or cold.