J. Kato et al., GENETIC-IMPROVEMENT OF ESCHERICHIA-COLI FOR ENHANCED BIOLOGICAL REMOVAL OF PHOSPHATE FROM WASTE-WATER, Applied and environmental microbiology, 59(11), 1993, pp. 3744-3749
The ability of Escherichia coli MV1184 to accumulate inorganic phospha
te (P(i)) was enhanced by manipulating the genes involved in the trans
port and metabolism of P(i). The high-level P(i) accumulation was achi
eved by modifying the genetic regulation and increasing the dosage of
the E. coli genes encoding polyphosphate kinase (ppk), acetate kinase
(ackA), and the phosphate-inducible transport system (pstS, pstC, pstA
, and pstB). Acetate kinase was employed as an ATP regeneration system
for polyphosphate synthesis. Recombinant strains, which contained eit
her pBC29 (carrying ppk) or pEP02.2 (pst operon), removed approximatel
y two- and threefold, respectively, more P(i) from minimal medium than
did the control strain. The highest rates of P(i) removal were obtain
ed by strain MV1184 containing pEP03 (ppk and ackA). However, unlike t
he control strain, MV1184(pEP03) released P(i) to the medium after gro
wth had stopped. Drastic changes in growth and P(i) uptake were observ
ed when pBC29 (ppk) and pEP02.2 (pst operon) were introduced simultane
ously into MV1184. Even though growth of this recombinant was severely
limited in minimal medium, the recombinant could remove approximately
threefold more P(i) than the control strain. Consequently, the phosph
orus content of this recombinant reached a maximum of approximately 16
% on a dry weight basis (49% as phosphate).