A bioreactor is for processing a fluid stream. The bioreactor may include a bioreaction chamber for receiving the fluid stream therethrough, a pair of spaced apart gas header assemblies within the bioreaction chamber for coupling to first and second gases, a first plurality of hollow fiber membranes (HFMs) extending between the pair of gas header assemblies for introducing the first gas into the fluid stream within the bioreaction chamber, and a second plurality of HFMs extending between the pair of gas header assemblies for introducing the second gas into the fluid stream within the bioreaction chamber.