Bioreactors for production and recovery of medium chain carboxylates from organic biomass are disclosed. Methods for improved production and recovery of medium chain carboxylates from organic biomass are also disclosed. The bioreactors can be used as a chain-elongation bioreactor, and a method of use thereof results in improved production and recovery of medium chain carboxylates from organic biomass. The bioreactor includes a shell defined by one or more walls and a length, and a plurality of porous hollow fiber membranes placed inside the reactor for continuous liquid-liquid extraction, as well as granular activated carbon (GAC) as biocarriers. The plurality of hollow fiber membranes is mounted such that a percentage of the length of the shell remains unoccupied by the plurality of porous hollow fiber membranes.