Optimal growth conditions and nutrient degradation characteristics of an aerobic denitrifying bacterium

Abstract

An efficient aerobic denitrifying bacterium, QX1, identified as Arthrobacter sp. by morphological observations, physiological-biochemical tests, and 16s rDNA sequence analysis, was isolated from burdock fields. A phylogenetic tree for this strain was built based on the 16s rDNA sequence, and the effects of nitrogen source, carbon source, pH value, and temperature on the growth of the strain, in addition to its denitrification characteristics, were evaluated. The results showed that under conditions of a gas bath with shaking at 160 rpm, suitable growth conditions for this strain were LB medium plus 1% acetic acid sodium, 30{degrees}C, and pH 8. With these conditions, the strain grew to the logarithmic phase after about 4 h, the logarithmic phase was maintained for 16 h, steady growth was observed for 24 h, and growth began to decline thereafter. QX1 exhibited alkali resistance and could tolerate low (15{degrees}C) and high temperatures (40{degrees}C). At 30{degrees}C, pH 8, and shaking at 160 rpm, strains could degrade nitrate, with a removal rate of 89.92% within 48 h in synthetic sewage. Thus, strain QX1 could have applications as an alkaline-tolerant, broad-spectrum temperature-tolerant, efficient denitrifying bacterium in the field of denitrification repair.