Abstract: In a method of continuously producing ethanol from sugar-containing substrates by fermentation of sugars by means of a flocculating strain of Zymomonas mobilis under anaerobic conditions and at a pH of from 4.5 to 7 a substrate is led commonly with Zymomonas mobilis cells through at least three fermentation stages without preceding sterilization, a concentration of at least 4% by volume of ethanol is maintained in each fermentation stage, a residence time of the fermentation medium in the entire system of maximally 31/3 h corresponding to a dilution rate of the fermentation medium in the entire system of at least 0.3 h.sup.-1 is adjusted, the Zymomonas mobilis cells are separated by sedimentation after the final fermentation stage, the Zymomonas mobilis cells are recycled into the first fermentation stage, and the ethanol-containing substrate separated from the Zymomonas mobilis cells is drawn off.

Abstract: There is disclosed an arrangement for growing permanent forms, of microorganism in particular filaments microorganisms. In order to design such an arrangement operationally safe, mobile and compact and with a high adaptability, yet for ensuring sufficiently large production and manipulation surfaces, the arrangement, in which trays for the culture medium are superposed in a box-type container, further includes a feeding chamber and an air-conditioning chamber containing an air-conditioning device united in a common housing. A gas-tightly closeable feed opening is provided in a side wall of the feeding chamber. The air-conditioning device includes sterile filters for sterile-keeping intake air and for filtering offsteaming exhaust air.