Isolation And Biochemical Characterization Of Three Psychrotrophic Denitirfying Removal Bacteria

In this study, the activated sludge from lab simulation CAST systemoperation has been enrichment and directional selection of denitrifying bacteria at lowtemperature, and three strains with different nitrogen removal characteristics oflow-temperature denitrifying bacteria, which were named LTD-03, LTD-05and LTD-16was isolated.LTD-03shows peculiar characteristics when growing in solid culture, it produced aflat and rough colony phenotype, color is opaque white, edge curl, the colony was soft,the optical microscope and scanning electron microscope showed that LTD-03forellipse globose, size of about40μm×90μm, no flagella; LTD-05shows a pillowcolony phenotype, color is lemon, edge smooth, shiny, soft bacteria colony, the ordinaryoptical microscope and scanning electron microscope showed that, LTD-05is spherical,diameter of about40μm, no flagella; LTD-16plate colony a pillow, grayish white,smooth, shiny, colony hard, waxy, the ordinary optical microscope and scanningelectron microscope found that LTD-16is long bacillus, length of about90μ m, noflagella. LTD-03is Gram-negative bacteria, LTD-05is Gram-positive bacteria, LTD-16is Gram-positive bacteria. Analysis by16SrDNA sequencing and sequence, LTD-03isPseudochrobactrum asaccharolyticum, LTD-05is Arthrobacter soli, LTD-16is Thaueramechernichensis, similarity reached99%.Through research on the growth characteristics of three strains of bacteria, threestrains were the best use of sodium acetate; optimum growth temperature ofLTD-03,and LTD-05were30℃, optimum growth temperature of LTD-16was40℃;the optimum pH range of three strains bacteria was7~9; Shaking culture growth andreproduction of the three conditions are subject to liquid volume and the optimumvolume of the solution is between300mL~400mL; LTD-03adaptation period of0~ 12h,12~36h in logarithmic growth phase, stable phase is36~52h, decline period is52~96h; LTD-05adaptation period is0~12h, the logarithm growth period is12~32H,stable for a period of32to40H, the decline period is40~96h; LTD-16adaptationperiod is0~8h,8~28h in the logarithmic growth phase, stable phase is28~36h, thedecline period is36~96h. Turbidimetry was used to measure the OD600value, themaximum OD600can reach above1.2.Three strains had wider temperature scope of application of denitrification, cancarry out denitrification in various temperature environments, but the denitrificationactivity of different temperature are different. At higher temperature denitrification rateis higher than the lower temperature, but at40℃denitrification began inhibiteddenitrification; rate of three strains in the nitrogen concentration of nitrate nitrogenunder high initial is far higher than the concentrations of nitrate and low initial; by coldacclimation, adapt to three strains of bacteria at low temperature and denitrification timewere compared with unacclimated strain short, removal rate than unacclimated strain;three strains of low-temperature denitrification ability are affected more by pH, theoptimum pH in the alkaline range; three isolates were not use or less use of ammonianitrogen, low denitrification but high concentration ammonia inhibited strains.Preliminary study on mixed bacteria strains found, nitrate removal rate were but wasdecreased, but the amount of nitrite nitrogen accumulation decreased significantly,highest do not exceed2mg/L.Three strains of bacteria have excellent denitrification effect at the low-temperature,therefore has a good prospect in the nitrogen system at low temperature.