Continuous-Culture Apparatus for Long-Term Use1

The continuous production and harvest of uncontaminated cells for periods of several months are a major requirement inthe design of a suitable culture system. Many continuous-culture units have been reported previously (1, 2), and some units are now commercially available. However, in these units, rubber, metals, and other sources of potentially toxic extractives are not prevented from direct contact with the culture. Factors that are toxic to some cells are known to leach from rubber stoppers, tubing, and some flexible polyethylenes (3). Even if these materials are nontoxic to the cells under culture, they are unknown factors in investigations of the cellular products of antibiotic or other biological activity. Most of the systems previously described use cotton filters for the exhaust gas. Since this gas is wet, the filters eventually become moist and permit microorganisms to penetrate the growth system. The coupling of components is another disadvantage of most systems. When glass tubing with ground glass joints is used throughout, the system is rigid and inconvenient in many respects. Plastic tubing, when stretched over glass tubing, frequently becomes distorted during autoclaving and thereafter forms an unreliable seal. Moreover, removal and replacement of tubing units is difficult. These problems were resolved in the construction of the system described below, which was used to maintain cultures of Chlamydomonas and Chlorella (unicellular algae) without contamination for periods of up to 4 months.