Continuous fermentation with yeast (Shizosaccharomyces pombe) floccules for ethanol production

This paper describes an experimental study of continuous fermentation of saccharified starch solution to produce ethanol with yeast particles of a highly flocculent strain of Schizosaccharomyces pombe, which were treated as immobilized microbial cells. Observations were initially made on yeast floccule characteristics during fermentation. An aeration-type fluidized-bed bioreactor that retained virtually all the yeast particles was built and operated continuously for 3 months. Bioreactor operation was found to be quite favorable for this fermentation system. The yeast concentration exceeded 40 g (dry mass)/liter; delivery of a limited amount of supplementary oxygen enhanced throughput to give levels as high as 20-24 g/liter.hr. The kinetic equations were also determined.