The processes of recombination of the photoexcited electron-hole pairs were studied in GaAs/AlGaAs weakly coupled multiple quantum wells, where the photoluminescence emission was composed of the contributions from the Γ-Γ and Γ-X conduction band minibands. Remarkable enhancement of the recombination time was observed when the magnetic field caused depopulation of the higher energy Γ-X miniband. The observed effect is attributed to the magnetic field induced variation of the electron density of states.