Mixed Cultures
Mixed cultures have also been investigated using pH-auxostats.
MacBean,
et al., (1979) showed an improvement in yogurt production with a
mutualistic relationship between two species that was only stable with
a pH-auxostat.
Von Schulthess, et al., (1990) were able to maintain
a pseudo-steady state of a mixed culture of S. cerevisiae and E.
coli. This was accomplished by pH setpoint changes that effectively
changed the maximum specific growth rate of each organism. The relative
concentration of each organism varied with time as one organism was dominant
over the other at a specific pH. The pH-auxostat has been promoted as a
tool for examining the dynamics of growth during changing environmental
conditions including temperature and substrate/product inhibition ( Larsson,
et al., 1990, Biebel, 1991,
Fraleigh, et al., 1989).