Continuous ethanol production byZymomonas mobilisin a fluidized bed reactor. Part II: Process development for the fermentation of hydrolysed B-starch without sterilization

✍ Scribed by D. Weuster-Botz; A. Aivasidis; C. Wandrey

• Publisher: Springer
• Year: 1993
• Tongue: English
• Weight: 843 KB
• Volume: 39
• Category: Article
• ISSN: 1432-0614
• DOI: 10.1007/bf00164450

✦ Synopsis

A continuous fluidized bed reactor operation system has been developed for ethanol production by Zyrnornonas rnobilis using hydrolysed B-starch without sterilization. The operation system consists of two phases. In the first phase macroporous glass carriers in a totally mixed fluidized bed reactor were filled up totally with a monoculture of Z. rnobilis by fast computer-controlled colonization, so that in the subsequent production phase no contaminants, especially lacticacid bacteria, could penetrate into the carrier beads. In the production phase the high concentration of immobilized Z. rnobilis cells in the fluidized bed reactor permits unsterile fermentation of hydrolysed B-starch to ethanol at short residence times. This results in washout conditions for contaminants from the substrate. Long-term experimental studies (more than 120 days) of unsterile fermentation of hydrolysed B-starch in the laboratory fluidized bed reactor (2.21) demonstrated stable operation up to residence times of 5 h. A semitechnical fluidized bed reactor plant (cascade of two fluidized bed reactors, each 55 1) was operated stably at a mean residence time of 4.25 h. Glucose conversion of 99% of the unsterile hydrolysed B-starch was achieved at 120 g glucose/1-1 in the substrate, resulting in an ethanol concentration of 50 g.1 -~ and an ethanol space-time yield of 13 g.l-~.h -~. This is a factor of three compared to ethanol fermentation of hydrolysed B-starch with Z. rnobilis in a continuous stirred tank reactor, which can only be operated stably under sterile conditions.