Construction Of Glycogen-accumulating Bacteria Model Under Different Phosphorus-limited Conditions And Study Of Its Metabolic Mechanis

Glycogen accumulating organisms(GAOs)have received much attention for their potential in organic matter removal,biological denitrification,and synthesis of intracellular stores polyhydroxyalkanoates(PHAs).However,it is still unclear about the construction mode of GAOs system,phosphate limitation factors and the growth pattern and metabolic characteristics of GAOs during system construction.Therefore,it is necessary to construct GAOs system under different phosphate limitation methods,investigate the community structure,metabolic characteristics and sludge character change pattern during system construction,and elucidate the influence mechanism of different phosphate limitation methods on GAOs system construction,operational stability and metabolism of the dominant intracellular storage molecules.In this paper,sequencing batch reactors(SBR)with different anaerobic-aerobic operation modes were used to study the process pattern of GAOs system construction and its metabolic mechanism in A and B reactors with different phosphate limitation modes.The results of carbon source conversion of the system showed that reactor A showed typical GAOs metabolism after 47 days of operation,that is glycogen consumption of 0.062 g Glycogen/g SS in the anaerobic phase,synthesis of 0.034 g PHAs/g SS PHAs by absorbing 268.9 mg/L organic matter,and PHAs degradation in the aerobic phase to synthesize glycogen and maintain microbial growth,and this process was not related to polyphosphate;increasing the influent P/C from 1/50 to3/50,the A-reactor system still maintained a stable GAOs metabolic profile and showed good operational stability.Under the B-reactor mode of operation and completely phosphate-restricted influent,after 140 days of system domestication,the construction of GAOs sysyem was not achieved,and the conditions are very unfavorable for the survival and growth of microorganisms,and the sludge properties of the reactor system are in a state of disintegration.However,when phosphate,necessary for microbial growth maintenance,was added to the B-reactor feeding with P/C ratio of 1/250,the reactor system gradually exhibited a typical pattern of GAOs metabolism after 29 days of operation,that is glycogen consumption of 0.046 g Glycogen/g SS in the anaerobic phase and synthesis of 0.043 g PHAs/g SS PHAs by absorbing 279.6 mg/L organic matter.In summary,the A-reactor operation mode was more favorable to the construction of the GAOs metabolic pattern under different phosphorus-limited conditions and to maintain the stable operation of the reactor.Macrogenomic techniques were used to analyze the community structure changes during the construction of GAOs system,and the results showed that the dominant GAOs in both A and B reactors were Candidatus Contendobacter,but there were significant differences in the evolution of the system sludge microbial community under different operation modes of A and B reactors.The relative abundance of Candidatus Contendobacter enriched in the A-reactor system was the highest at 16%of the system;and after increasing the phosphate concentration in the influent water,the dominant bacteria in the system were still Candidatus Contendobacter,whose relative abundance was maintained at about 12%.B reactor under fully phosphate limiting operating conditions,the microbial population fluctuates,the system is dominated by Thauera,the abundance of GAOs has been at a low level,when the system mainly relies on the tricarboxylic acid(TCA)cycle to maintain the minimum survival requirements;the relative abundance of Candidatus Contendobacter reached30% after the system was stabilized.Glycogen of the anaerobic phase of Candidatus Contendobacter was involved algal sugar synthesis,making the glycogen consumption of the anaerobic phase of the system greater than that of other GAOs models.This study compared the differences in the construction process of GAOs model under different phosphorus limitation methods,which on the one hand laid a theoretical foundation for the establishment of an effective reactor model for the study of GAOs,and on the other hand further improved the biometabolic mechanism of GAOs.