Asl. Pauli et S. Kaitala, OPTIMAL-GROWTH CONDITIONS FOR ACINETOBACTER ISOLATES FROM ACTIVATED-SLUDGE TREATING FOREST-INDUSTRY WASTEWATERS, Applied microbiology and biotechnology, 43(4), 1995, pp. 746-754
Three Acinetobacter isolates (identified by API 20 NE as A. baumannii,
A. junii, A. Iwoffii) from activated sludge treating forest-industry
wastewaters were used as model organisms for polyphosphate-accumulatin
g bacteria to optimize growth conditions for acinetobacters. The optim
al concentrations of carbon, nitrogen, phosphorus, magnesium and potas
sium for the growth of these isolates were determined by using four se
ts of factorially designed experiments, Maximum growth was obtained wi
th an average C:N:P ratio of 100:14:1.5 (on a weight basis) in the med
ium. The average N:P ratio of about 10 is twice the ratio that is usua
lly considered optimal for bacterial growth in activated sludge. Magne
sium and potassium are crucial for polyphosphate metabolism. A. bauman
nii did not respond to either magnesium or potassium additions, and A.
junii had a linear response to potassium. Comparison of the optimal m
olar Mg:P (0.93-1.8) and K:P (0.56) ratios obtained for A. Iwoffii and
A. junii in the experiments to the corresponding ratios in the influe
nt wastewaters indicates that magnesium and potassium would not limit
growth and concomitant polyphosphate formation in acinetobacters. The
results based on the optimal concentrations of elements in the medium
may provide a better basis for optimizing the growth conditions than d
ata on the chemical composition of bacterial cells.