TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Membrane: In the membrane above, the diffusion of the nutrient solution occurs without the external application of pressure. One of the opposing surfaces comprises a gas face and the other comprises a nutrient face. Preferably, the biolayer comprises biological matter selected from bacteria, fungi, animal cells, mammalian cells plant cells, protozoa, other biological matter, prokaryotic cells, or eukaryotic cells.Preferred Bioreactor: In the bioreactor above, the membrane is supported vertically. The membrane-supporting structure supports the membrane in a configuration in which a portion of the membrane is parallel to another portion of the membrane to define an inside region between the two portions. The membrane-supporting structure supports more than one membrane, the membranes being arranged in pairs so that each pair is joined to define an inside region between the two membranes of the pair. The bioreactor has one or more spacers for maintaining a distance between the two portions or between the membranes. It also comprises an inlet for admitting the nutrient solution to the nutrient face of the membrane, an outlet for removing the nutrient solution from the nutrient face of the membrane, and a recycling system for recycling the nutrient solution from the outlet to the inlet. The recycling system is capable of preventing access of oxygen to the liquid. The bioreactor also comprises an oxygen remover for removing oxygen from the nutrient solution. It further comprises means for removing solid matter from the membrane.Preferred Method: Making a membrane having an immobilized biolayer on a gas face comprises:(a) immobilizing biological matter on a membrane away from a nutrient face of the membrane, the membrane being capable of allowing diffusion of a nutrient solution from the nutrient face to the biological matter; and(b) providing the nutrient solution to the nutrient face of the membrane and exposing the gas face of the membrane to a gas under such conditions that the biological matter forms an immobilized biolayer on the gas face, where the membrane is accessible so as to enable removal of cells from the immobilized biolayer once formed.The gas contains oxygen. The nutrient solution is substantially anoxic. The membrane is selected from a nanoporous membrane, a mesoporous membrane, a microporous membrane, or a membrane having a combination one or more of nanoscale, mesoscale, and microscale pores. Preferably, the membrane is the membrane above. Immobilizing comprises exposing the membrane to cells or spores so that at least some of the cells or spores become attached to it. Providing the nutrient solution comprises removing oxygen from the nutrient solution. Immobilizing also comprises infusing a precursor liquid into the support material, the precursor liquid being capable of generating a nanoporous solid or gel; and generating the nanoporous solid or gel on and/or in the support material to form a membrane. The precursor liquid comprises cells or spores, where the process of generating the nanoporous solid or gel immobilizes at least some of the cells or spores within the membrane. The process also comprises exposing the support material either to an alkaline aqueous solution or to a water plasma prior to the infusing step. The precursor liquid comprises colloidal silica and generating the nanoporous solid or gel comprises changing the pH of the precursor liquid infused in the support. Operating the bioreactor comprises exposing the nutrient face of the membrane to a nutrient solution, exposing the biolayer to a gas, and allowing the nutrient solution to diffuse from the nutrient face of the membrane to the biolayer. Allowing the nutrient solution to diffuse is performed without the application of external pressure. The biolayer and the composition of the nutrient solution are chosen for a purpose selected from producing pharmaceuticals, producing antibodies, producing vaccine components, producing food material, producing cells, producing enzymes, or for the purpose of removing, degrading, or converting components in the nutrient solution. The method also comprises removing oxygen from the nutrient solution. It also comprises isolating a product of the bioreactor. Isolating comprises separating the product from the nutrient solution, or harvesting solid matter from the gas face. The method further comprises introducing a second liquid to the nutrient face of the membrane, exposing the membrane to the second liquid for a second period of time, and separating a product from the second liquid.