Abstract: A membrane bag comprising a volume for permeate collection, wherein the volume is completely enclosed in seamless membrane substance; a filtration unit comprising at least one above-described seamless membrane bag; the use of at least one above-described seamless membrane bag in a membrane bioreactor; the use of at least one above-described seamless membrane bag in water filtration or waste water purification; and the use of at least one above-described seamless membrane bag for the filtration or separation of a mixture of fluids, vapors and particles.