PFRs for running multiphasic processes are disclosed. The PFRs are single or multi-chamber devices having at least three types of regions (a liquid-contacting region, a gas-contacting region and a Ssquid-coSection region), and a porous substrate providing fluid communication at least between the liquid-contacting and gas-contacting regions. Removal of liquid from the porous substrate, such as by collecting the liquid as it flows off the bottom of the porous substrate in the Siquid-coSSection region or such as by evaporation of the liquid from the porous substrate in the evaporation region supports a continuous flow process. Methods of using the PFRs are also disclosed, for example methods of using the PFRs as photobioreactors for cultivating photosynthetic microorganisms, for producing fermentable sugars, for producing ethanol, for fermenting synthesis gas and producing single cell protein from natural gas.