Polyvinylidine fluoride (PVDF) hollow fiber membranes were employed to enhance mass transfer rate ofmethane in water for the fermentation of Methylosinus trichosporium OB3b. Compared to commonalumina bubbler, hollow fiber membrane modules (HFMMs) afforded smaller methane bubble size andlarger methane–water volumetric mass transfer coefficient (kLa) as high as 150.1 h 1. Furthermore, cellgrowth rate and maximum optical density of M. trichosporium OB3b were increased by 67.3 and 77.4%,respectively, by adapting forty HFMMs, compared to those of alumina bubbler.