The operational flexibility of the phased culture technique, as observed by changes in the cell cycle of Candida utilis

Abstract

The operation of a continuous phasing technique was examined with regard to synchrony and growth of Candida utilis at different doubling times. A nitrogen-limited medium and an energy-limited medium were compared. Numbers of viable cells, dry mass, ribonucleic acid (RNA), deoxyribonucleic acid (DNA), various phosphorus-fractions, and protein were measured.In a nitrogen-limited medium the continuous phasing technique provided good synchrony (65%–80%), and permitted control and variation of the doubling time up to 9 h. Dry mass, various P-fractions, and DNA increased linearly during all cycle times. The cell doubling time was adjustable to the cycle time imposed by the technique. The nitrogen source was always assimilated within 4 h, whatever the length of the cycle employed. The associated pattern of changes in the amino acid pool, protein, and RNA contents of the cells, though characteristic, underwent some modifications with change in doubling time.An inverse relationship between the amount of nitrogen available to the cells for their reproduction and the corresponding doubling time was found.In an energy (glucose)-limited medium the technique appeared to be restricted to a doubling time where the energy source in the medium lasted until the end of the cell's life cycle. The degree of synchrony was 70–75%. A variation of the doubling time by the technique did not seem possible in glucose-limited medium since no adjustment of the growth rate to the imposed cycle time could be observed.