Fig. 1

Set-up of the membrane-based fed-batch shake flask. a The offline (left) and the online (right) membrane-based fed-batch shake flasks have a reservoir system to enable the continuous supply of substrate to the culture broth. b Membrane tip type A requires an additional silicone ring, which spans the membrane on the tip; with the membrane tip type B the membrane is screwed between the cap and the body of the membrane tip