Biological phosphorus removal by pure culture of Lampropedia spp.

Lampropedia spp. is a Gram-negative, Neisser-positive coccus that was isolated from EBPR (enhanced biological phosphate removal) activated sludge laboratory plants operating on dairy and piggery wastewaters. In aerobic growth tests carried out on sodium acetate, Lampropedia spp. stored PHB up to 12% w/w. Biomass yield was estimated at 0.55 g VSS.g−1 HAc and specific growth rate at 0.045 h−1. The experimental maximum acetic acid removal rate was 71.86 mg HAc.g−1 VSS.h−1 with a semisaturation constant of 71.78 mg.l−1. Batch tests were carried out to check whether Lampropedia spp. was capable of enhanced biological phosphorus removal. Under anaerobic conditions, Lampropedia spp. sequestered acetate and stored PHB with an average conversion factor of 0.33 mg PHB.mg−1 HAc. The measured maximum PHB storage capacity was 31% w/w, with a maximum specific PHB accumulation rate of 17 mg PHB.g−1 VSS.h−1 and a specific anaerobic acetate uptake rate of 57 mg HAc.g−1 VSS.h−1. The experimental ratio between phosphorus released and acetate taken up was low, on average 0.044 mg PO4-P.mg−1 HAc, with a specific rate ranging from 1.7 to 3.6 mg PO4-P.g−1 VSS.h−1 at pH 7.5. Despite the low figure, fractionation analyses showed that in anaerobic conditions the released phosphate comes from cell polyphosphate degradation. Therefore, all the results allow us to conclude that Lampropedia spp. can be classified amongst the phosphorus accumulating bacteria