“…Hollow-fiber modules (Manjarrez et al, 2000 ) could connect well-stirred bioreactors (glass, polymer, stainless stell,..) that would each contain one or multiple microbial species accomplishing part of biochemical transformation. The flow of media and intermediate products between bioreactors could be controlled by applying pressure into the headspace of each vessel (Manjarrez et al, 2000 ) or using pumps (e.g., peristaltic,..) (Doran, 2012 ; Stanbury et al, 2017 ). Additionally, the cells could be even further confined and separated from the bulk of the medium by cellulose dialyzing membranes (Gerhardt and Gallup, 1963 ; Aida and Yamaguchi, 1966 ; Pörtner and Märkl, 1998 ; Ohno et al, 1999 ), or in dialysis tubing (Baker and Herson, 1978 ; Turley and Lochte, 1985 ; Gehin et al, 1996 ; Guedon et al, 1999 ), and those “sausages” could be placed inside each bioreactor.…”