Auxostats For Continuous Culture Research Paper


Various methods of continuous flow culture of Clostridium acetobutylicum NCIB 8052 were investigated, with the aim of obtaining prolonged production of acetone and butanol. In ammonia-limited chemostat culture, maximal concentrations of solvents were obtained at pH 5–5 at a relatively high biomass concentration of 1.3–2.0 g/1 dry weight maintained at a dilution rate of 0.06/h. Similar dependence of solvent production on the sustenance of a relatively high cell density was observed in magnesium- or phosphate-limited chemostat cultures. Solvent production was always transient, however, with a shift to production of only acetic and butyric acids being observed after 4–16 volume changes. Longer term solvent production was obtainable under conditions of glucose limitation but the solvent yield was low. Cultivation in a pH-auxostat permitted solvent production in reasonably high yield over at least 70 volume changes with no signs of culture degeneration. Although none of the continuous flow cultures achieved a true steady state, we conclude that turbidostat or pH-auxostat culture are the methods of choice for continuous solvent production by Cl. acetobutylicum NCIB 8052.

An auxostat is a continuous culture device which, while in operation, uses feedback from a measurement taken on the growth chamber to control the media flow rate, maintaining the measurement at a constant.

Auxo was the Greek goddess of spring growth, and as a prefix represents nutrients. However, the most typical auxostats are pH-auxostats,[1] with feedback between the growth rate and a pH meter.

Other auxostats may measure oxygen tension, ethanol concentrations, and sugar concentrations [2]


  1. ^Larsson G, Enfors SO (1990). "The pH-auxostat as a tool for studying microbial dynamics in continuous fermentation". Biotechnology and Bioengineering. 36 (3): 224–232. doi:10.1002/bit.260360303. PMID 18595072. 
  2. ^Gostomski P, Muhlemann M, Lin YH, Mormino R, Bungay H (1994). "Auxostats for continuous culture research". Journal of Biotechnology. 37 (2): 167–177. doi:10.1016/0168-1656(94)90008-6. 

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