Characterization and toxicity of a phosphate-binding exobiopolymer produced by Acinetobacter haemolyticus MG606

A novel, phosphate-binding exobiopolymer (EBP) produced by Acinetobacter haemolyticus MG606 was characterized and its biocompatibility evaluated in RAW 264.7 cells and in mice. EBP was identified as a 50 kDa heteropolysaccharide composed of pentose and hexose sugars. EBP exhibited cytotoxicity, stimulation of free radical production and loss of mitochondrial and lysosomal integrity in RAW 264.7 cells at 500 μg/mL concentration while lower concentrations exhibited no significant (p > 0.05) effect on these parameters. EBP exhibited dose-dependent mortality, body weight reduction, hypothermia and clinical signs of toxicity in mice following intraperitoneal administration. The LD₅₀ of EBP was determined to be 92.31 mg/kg. Overall, the results of our study suggest that composition of EBP produced by A. haemolyticus MG606 is distinct from EBP produced by other Acinetobacter spp. The high biocompatibility supports application of EBP as a safe biosorbent for phosphate remediation.