Zero-growth bioprocesses: A challenge for microbial production strains and bioprocess engineering.

Microbial fermentation of renewable feedstocks is an established technology in industrial biotechnology. Besides strict aerobic or anaerobic modes of operation, novel innovative and industrially applicable fermentation processes were developed connecting the advantages of aerobic and anaerobic conditions in a combined production approach. As a consequence, rapid aerobic biomass formation to high cell densities and subsequent anaerobic high-yield and zero-growth production is realized. Following this strategy, bioprocesses operating with substantial overall yield and productivity can be obtained. Here, we summarize the current knowledge and achievements in such microbial zero-growth production processes and pinpoint to challenges due to the complex adaptation of the cellular metabolism during the cell's passage from aerobiosis to anaerobiosis.