1987 Volume 12 Issue 1 Pages 22-32
Recent research progresses on membrane technologies to fermentation production processes are reviewed. First, a cross flow filtration of suspended yeast cells by a hollow fiber module was carried out to enhance the ethanol productivity in repeated fedbatch culture. The ethanol productivity obtained in this system was 11.3g ethanol/litre/h compared to 3 in a conventional Melle-Boinnot method. Second, in ethanol fermentation, an immobilized yeast cells system capable of forced permeation of the medium was developed in contrast to conventional immobilized yeast cell system where the mass transfer depends on “diffusion”. In this new system, the cell density on the surface of gel (1 mm thickness) became 1.7×1010 cells/ml gel compared to 4×109 in the conventional system. Hence, the ethanol productivity in this system could increase 60g ethanol/ litre gel/h compared to 20 to 30 in conventional packed bed systems. Third, acetic acid fermentaion from ethanol was conducted in a hollow fiber module bioreactor where the bacterial cells absorbed on the fiber surface could consume oxygen running through the inside of hollow fiber and ethanol running through the outside the fiber. Thus, a mimic vineger production of conventional surface cluture could be established with a remarkable increase of the surface area per reactor volume. Finally, a sulfonated polysulfone membrane was used for in situ regeneration and retention of coenzymes NADP (H) using xylose reductase coupled with oxidoreductase system in the reduction of xylose to xylitol with hydrogen gas. The membrane could almost completely reject the permeation of NADP (H) and F420 and the required enzymes, but not reject for permeation of xylitol.
