Continuous operation of a pressure-cycled membrane bioreactor

A membrane bioreactor system has been used to continuously ferment glucose to eth‐anol with Saccharomyces cerevisiae and extract the product into a solvent, tributyl phosphate. The reactor cycles gas pressure to force a convective flux of nutrient into the cell chamber and product out. The reactor has been run for over 3000 h with minimal deterioration of operating characteristics after the first hours of operation. A corn starch hydrolysate was also fermented, yielding similar results. Zymomonas mobilis was tested as an alternative catalyst, but it formed filaments that reduce the effectiveness of the pressure cycle. Z. mobilis appears to be less attractive than S. cerevisiae for such a reactor.