Kinetics of growth and phosphate uptake in pure culture studies of Acinetobacter species

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Abstract
Acinetobacter has been found to be the major species responsible for mediating biological phosphate removal. The growth kinetics and phosphate uptake were investigated for an isolated Acinetobacter strain growing in a defined medium. The phosphate uptake is dependent on growth rate, temperature, and pH. Polyphosphate granules occurred in a balanced growth stage. The maximum phosphorus content in cells was 4.8% at the dilution rate of 12 day−1. The specific phosphate uptake rate was found to be a quadratic polynomial function of the dilution rate. Increased calcium (up to 36 mg/L) and magnesium (up to 15 mg/L), and the addition of yeast extract (100 mg/L), primary effluent (20%), and fluoride (10 mg/L) did not affect phosphate uptake. Anaerobic conditioning (N2 stripping), low pH (CO2 stripping), and addition of sodium acetate under anaerobic conditions failed to stimulate immediate phosphate release. Nevertheless, After 21–24 h, the phosphate release was ca. 3, 5, and 15 mg P/g cell, respectively, for N2 purging, the addition of acetate, and CO2 purging. For two‐stage completely stirred reactor operation, there was negligible phosphate overplus at the second reactor when phosphate was added, when the first reactor was subjected to phosphate limitation. When both phosphate and carbon limited the growth in the first reactor, there was slight phosphate accumulation under endogenous respiration conditions in the second reactor.