Key factors for growth and phosphate uptake by Acinetobacter tjernbergiae

Phosphorus-containing fertilisers are essential for global food production but depend on finite phosphate rock reserves. Recovery of phosphorus from waste streams, such as those in wastewater treatment plants, will be required to follow future regulations. Certain Acinetobacter spp. can accumulate 24-30% (w w^-1) of phosphate intracellularly, making them promising candidates for microbial phosphorus recovery. However, previous studies have reported insufficient biomass formation to enable rapid phosphate uptake. Therefore, this work investigated key factors of biomass generation and phosphate uptake of Acinetobacter tjernbergiae in an empirical study. Increasing iron concentration by 1 mg L^-1 enhanced growth six-fold in shake flask cultivations. A maximum biomass concentration of 12 ± 0.7 g L^-1 was achievable during 14 h of bioreactor cultivation. The maximum volumetric phosphate uptake rate (r_S,P) reached 280.2 ± 40.8 mg (L h)^-1, the highest value reported so far for Acinetobacter spp., while specific rates of up to 41.0 ± 1.1 mg (g h)^-1 were achieved. It was further shown that A. tjernbergiae exhibits both polyphosphate accumulation and the overplus phenomenon. Moreover, phosphate uptake was strongly correlated with carbon uptake, while carbon absence resulted in phosphate release.