Although biochemical models for the Pi accumulation of Acinetobacter have been discussed in the literature, attention should be given to the fact that a wastewater treatment plant implies a mixed population of microorganisms and acetate and other low molecular weight fatty acids are not the only nor the most abundant carbon source available. Other microorganisms known to be present in activated sludge plants are able to accumulate polyP, PHB and/or carbohydrates. These bacteria (Pseudomonas, Aeromonas, Moraxella, Klebsiella, and others) may use acetate, but also glucose and other monosaccharides, amino acids, fatty acids and other substances as carbon sources, not only for a fermentation process, but also for the intracellular synthesis of polyP in an aerobic stage, and the release of Pj in the anaerobic one. Though most of the experimental work found in the literature was done using mixed cultures, it is proposed that the main differences in the biochemical models is due to the lack of the definition of the specific substrate transport mechanism across the cellular membrane.

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