Development and application of a system for analysis of mixed cultures of microorganisms

Development and application of a system for real-time quantitative assessme nt of individual cell activities in a mixed culture system was investigated . This was based on a concept that the activities of individual cells in a mixed culture can be assessed if the cells are physically separated (in sep arate compartments) in a vessel while the culture conditions, including the broth components, are maintained the same in all the compartments during t he cultivation. On this basis, three different apparatus (M-1, M-2, and M-3 ) were constructed using various types of membranes. In terms of mass trans fer characteristics and membrane fouling, the M-3 apparatus was the most ef fective system for analysis of mixed cultures at high cell densities. With the M-3 apparatus, the interrelationships between two alcohol-producing str ains (Saccharomyces cerevisiae and Zymomonas mobilis) under anaerobic and a erobic conditions were studied. Under anaerobic condition, except for possi ble competition for nutrients, there were no significant effects of the act ivities of one microorganism on the other. However, under aerobic condition , amensalism was observed because acetaldehyde that was produced by Z. mobi lis inhibited the growth of S. cerevisiae.