| 摘要 |
Low aliphatic alcohols or organic solvents, especially ethanol are continuously produced by fermentation from sugar containing nutrient substrates. The process includes two fermentation steps or stages in which the substrate is subjected to the effects of microorganisms such as yeast. The first fermentation stage has a volume of 10 to 20% of that of the second fermentation stage. By adjusting the environmental conditions in each stage a large cell growth with a small portion of the total supplied substrate quantities takes place in the first activation stage and a high product formation rate is achieved with a considerably larger portion of the entire supplied substrate quantity in the second production stage. A partial outflow stream from the first stage is microfiltered and the permeate as well as the unfiltered outlet flow of the first stage, is directed into the second stage. The outlet flow of the second stage is microfiltered and the concentrate is partly discharged as a product output stream and partly returned to the second stage. The transfer flow and return flow streams and the discharge of the permeate and the product streams from the second stage are adjusted so that, for dwell times of the cell mass of up to two hours in the first stage and up to 15 hours in the second stage, an average cell age of 40 to 100 hours is achieved with a corresponding high yield output.
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