Changes in pH of an Anaeroboic Bacterial Culture Grown in a 3 L Bioreactor and Amended with Oxyanions of Selenium
Cultures of Pseudomonas fluorescens strain K27 were grown into stationary phase in anaerobic cultures on a complex medium with 3% nitrate. Cell population, measured by optical density, and pH were determined hourly in time course experiments that extended over 8 to 10 hours. Cultures were amended with either selenate, selenite or mixtures of these oxyanions. Selenite appears to be more toxic than selenate as measured by specific growth rate. Selenium-free controls of this faculatative anaerobe dropped from an initial pH of 7.4 to 7.2 while growing into stationary phase. Ten mM selenite-amended cultures increased in pH to about 8; while 10 mM selenate-amended cultures remained basically at the pH of the initially inoculated medium. No significant trend in pH was apparent among the five different amendements regimes run in triplicate; however the largest variability among replicates was for non-equimolar mixtures of selenate and selenite.