Abstract: A method of producing a secondary metabolites comprises providing a porous substratum which has a biofilm of micro-organism attached thereto, and causing a nutrient solution to flow through the substratum, at a rate which is sufficiently low for a nutrient gradient to be established across the biofilm, such that the nutrient concentration at a high level along the gradient is sufficiently high to support primary growth of the micro-organism, and the nutrient concentration at low level along the gradient being sufficiently low to induce secondary growth of the micro-organism, thereby to produce secondary metabolite. The substrate is in the form of a hollow fibre membrane having a relatively thin, porous skin on the inside, and a relatively thick, finger-like, externally unskinned void structure radiating outwardly from the skin.

Abstract: A method of making a hollow fiber membrane comprises extruding a membrane-forming polymer solution through the annulus of a tube-in-orifice spinneret (12) to form a nascent hollow membrane (32), there being a lumen coagulant in the lumen of the nascent membrane, and the outside of the nascent membrane being contacted with an external coagulant (34). The external coagulant has a solvent content which is such that, at the interface between the nascent membrane and the external coagulant, liquid--liquid phase separation rather than gelation is thermodynamically the favored process, and the membrane is then subjected to a vapor-phase non-solvent environment to induce precipitation of the phase-separated polymer.