GENETIC APPROACH TO ENHANCED BIOLOGICAL PHOSPHORUS REMOVAL

Genetic improvement of bacterial ability to accumulate phosphate (Pi) was investigated using Escherichia coli as a test organism. High level s of Pi accumulation were achieved by (i) modifying the genetic regula tion and increasing the dosage of the E. coli genes encoding polyphosp hate kinase (ppk), acetate kinase (ackA), and the phosphate inducible transport system (pstS, pstC, pstA, and pstB) and (ii) genetically ina ctivating ppx encoding exopolyphosphatase. Acetate kinase was employed as an ATP regeneration system for polyphosphate synthesis. The best r ecombinant strain, which contained both pBC29 (ppk) and pEP02.2 (pst g enes) accumulated approximately 10-fold more Pi than did the control s train. The phosphorus content of this recombinant reached a maximum of 16 % on the dry weight basis (49 % as phosphate). About 65 % of the c ellular phosphorus was stored as polyphosphate.