[Characteristics of the extracellular polymeric substances of a heterotrophic nitrifying bacterium strain]

To study the variation of extracellular polymers substances (EPS) composition of the heterotrophic denitrifying bacteria (Acinetobacter sp. YY-5) at different growth stages, The EPS of YY-5 was extracted by thermal, and the composition of protein, polysaccharides, nucleic acid and free amino acids were analyzed at different growth stages. Subsequently, the proteins in extracts were hydrolyzed into amino acids, the amino acid's changes and effect on physical and chemical properties of proteins were investigated. The results showed the strain has a high EPS contents which mainly consist of proteins, and the EPS content achieved the highest value at stable stage. The amount of proteins increased from 14.599 mg x g(-1) to 28.489 mg x g(-1), then declined to 15.139 mg x g(-1). Polysaccharides content increased from 6.757 mg x g(-1) to 10.199 mg x g(-1), then declined to 7.857 mg x g(-1). The nucleic acid contents increased from 1.56 mg x g(-1) to 6.287 mg x g(-1) in the whole growth stages. The free amino acids contents increased from 3.713 mg x g(-1) to 4.374 mg x g(-1), then obviously declined to 1.299 mg x g(-1). After the proteins were hydrolyzed into amino acids, the amount of polar amino acids showed the trend that increased earlier and declined later, the contents of nonpolar amino acids increased at all growth stages. The amino acids with negative charges were more than that with the positive.