Fed-batch

For small-scale laboratory experiments batch culture is ideal.  However, relative to the time that the organism is growing the time taken to prepare the equipment for another experiment is long. The flask must be sterilized, refilled with medium, cleaned, autoclaved and another inoculum prepared before another experiment can starts. This time can be minimized if the majority of the biomass and spent medium is poured away or removed by pumping and fresh medium is added directly to the flask. The residual biomass serves as the inoculum for the next growth cycle. Although this is attractive in terms of reducing down time it increases the number of interventions in the experiment and therefore the possibility of contamination increases as well. In situations where the culture itself is undefined such as during enrichment of microorganisms with a particular property then contamination can be seen to be a smaller problem. However, the  possibility still remains that toxic metabolites will not  be sufficiently diluted through the fresh medium to allow exactly the similar growth parameters after feeding compared with the primary culture.