Fluidized‐Bed Bioreactors Using a Flocculating Strain of Zymomonas mobilis for Ethanol Production

Abstract

A recently isolated strain of Zymomonas mobilis (NRRL B-12526) has been shown to form stable floc particles that can effectively convert glucose to ethanol at rates in excess of 400 g/l/hr in a fluidized-bed bioreactor. Preliminary results indicate that such a system, yielding particles which are in the size range of 0.5 to 1mm, may have extremely high productivity, even higher than Saccharomyces cerevisiae. However, the system is so reactive that the CO/sub 2/ off-gas makes it difficult to maintain a high biomass loading in the upper part of the reactor. This lower biomass content results in a decreased ethanol productivity, which approaches 100 g/l/hr for the entire active reactor volume when over 95% of the glucose is metabolized.