Effect Of Coenzyme ? Regulated By Carbon Source And NAD~+ Precursor On Intracellular Polymerization Of PAOs

Biological phosphorus removal has always been a hot issue in domestic water science and technology research.The regulation of intracellular polymer metabolism is an effective way to improve the efficiency of biological phosphorus removal.Nicotinamide adenine dinucleotide(coenzyme I,NADH reduced state,NAD~+oxidation state)is an extremely important factor regulating the intracellular redox reaction,Therefore,regulating the level of intracellular coenzyme I changes the metabolism of phosphorus accumulating organisms(PAO_S)intracellular polymer is a new idea to improve the efficiency of biological phosphorus removal.However,there are few studies on regulating the intracellular polymer metabolism by adjusting the coenzyme I levels of PAO_S.The study screened a strain of polyphosphate by anaerobic/aerobic alternate culture combined with blue-white spot screening.For the screened PAO_S,Coenzyme I was regulated by exogenous regulation methods such as changing carbon source and adding different concentrations of nicotinic acid,to investigate the effects of carbon source and nicotinic acid on the regulation of intracellular coenzyme I in PAO_S and on the metabolism of intracellular polymer.The main findings are as follows:(1)Rapidly enriching PAO_S by anaerobic/aerobic alternating operation and using anaerobic/aerobic alternating plate iterative culture,and combined with BCIP(5-bromo-4-chloro-3-indolyl-phosphate)for blue-white spot screening and staining of heterochromatic particles and PHB(poly-?-hydroxybutyric acid),a total of 14 strains of PAO_S including ZWC-1,ZWC-2,ZWC-3,ZWC-4,ZWC-5,ZWC-6,ZWC-7,ZWC-8,ZWC-9,ZWC-10,ZWC-11,ZWC-12,ZWC-13 and ZWC-14 were screened.Test the phosphorus removal performance of 14 strains of PAO_S,The test results show that the phosphorus removal rates were 44.5%,45.5%,77.5%,71.2%,47.3%,80.4%,76.6%,54.7%,76.2%,71.9%,43.6%,58.6%,75.6%,48.4%,respectively.In this test,PAO_S of ZWC-8 was selected as the research object.(2)The PAO_S of ZWC-8 were identified by Gram staining,Scanning electron microscopy,16S rDNA sequence analysis and homology comparison.Gram staining results showed that the ZWC-8 strain was a Gram-negative bacteria;Scanning electron microscopy showed that the strain size was(0.4?0.5)?m×(1.5?2.5)?m;16S rDNA sequence analysis and homology identification indicated that it was Acinetobacter oleivorans.(3)Different carbon sources(glucose and sodium acetate)were used to regulate the intracellular coenzyme I of PAO_S to study its effect on the intracellular polymer metabolism of PAO_S.The results showed that the content of NADH per unit mol C was2.765?mol/g and the content of NAD+was 3.028?mol/g,which was higher than the1.403?mol/g NADH content and 1.587?mol/g NAD~+content per unit mol C of glucose system,and the sodium acetate system NAD+/NADH is 1.095 higher than the glucose system 1.058;In the sodium acetate system,the amount of PHB synthesis and the amount of poly-P hydrolysis in the aerobic section,the consumption of PHB and the poly-P synthesis amount in the aerobic section are higher than those in the glucose system,but the consumption of anaerobic glycogen in the glucose system is higher than that in the sodium acetate system,in which the consumption of glycogen may be related to the synthesis of PHV;The average phosphorus removal efficiency of the sodium acetate system was 59.73%higher than the 51.41%of the glucose system.(4)Different concentrations of nicotinic acid(0 mg/L,4 mg/L,8 mg/L,12 mg/L)were used to regulate the intracellular coenzyme I levels of PAO_S,to study its effect on the intracellular polymer metabolism of PAO_S.Different concentrations of nicotinic acid have certain effects on the intracellular NADH and NAD~+levels of PAO_S.The average content of intracellular NADH in different nicotinic acid concentrations was1.791?mol/g,2.392?mol/g,2.613?mol/g,2.633?mol/g,and the average NAD~+content was 1.962?mol/g,2.780?mol/g,3.136?mol/g,3.346?mol/g;the results show that with the increase of niacin concentration,NAD~+content increased significantly,NADH content increased relatively;with the increase of niacin concentration,NAD~+/NADH were 1.095,1.162,1.200,1.270;With the increase of NADH and NAD~+content,the synthesis amount of PHB and the amount of poly-P hydrolysis in anaerobic section,the consumption of PHB and the amount of poly-P synthesis in aerobic section increased continuously;The phosphorus removal efficiency of the strains increased continuously,reaching 59.73%,70.48%,73.11%,and 76.13%,respectively.(5)Intracellular Coenzyme I levels have great influence on the phosphorus removal efficiency of PAO_S.With the increase of NAD~+/NADH,the higher the synthesis and conversion of PHB and poly-P in the polyphosphate bacteria,the higher the phosphorus removal efficiency of the polyphosphate bacteria.The NAD~+/NADH increased from 1.058 to 1.270,and the phosphorus removal efficiency of the strain increased by 24.72%.Coenzyme I is a key coenzyme in the intracellular phase of PAO_S,The experiment regulated the metabolism of polyphosphor intracellular polymer by using different carbon sources and NAD~+precursors to regulate NADH and NAD~+levels,effectively improve the efficiency of biological phosphorus removal,This research provides a new idea for strengthening biological phosphorus removal,which has certain practical significance and theoretical value.