Production of Secondary Metabolites and Exopolysaccharides by Azotobacter in Mercury-Contaminated Media

Abstract

The rhizobacteria of Azotobacter genera is possibly has a dual role as bioremediation agent and biofertilizer, due to its production of exopolysaccharides (EPS) that chelates heavy metal, and secondary metabolites that assist in enhancing plant growth. The aim of this research is to assess and ability of Azotobacter consortia to synthesis the EPS, phytohormones and organic acids in Hg-contaminated liquid culture. The experiment conducted in completely randomized design to test four concentration of Hg in N-free Ashby broth i.e. 100, 200, 300 and 400 mg L^-1. The bacterial culture were incubated at room temperature, for 72 h on the 100-rpm gyratory shaker. All treatments were replicated three times.  At 72 h after incubation, total Azotobacter population as well as auxin, gibberellins, cytokinins, organic acids, and EPS content were analyzed. Research indicated that the Azotobacter consortia could survive in the media contaminated with 400 mg L^-1 Hg with a total population of 6.20 log CFUmL^-1, and producing auxin of 2.84 mgL^-1, gibberellins of15.09 mgL^-1, cytokinin of 1.53 mgL^-1, oxalic acid of 0.61 mgL^-1, citric acid of 0.91 mgL^-1 and EPS of 22 gL^-1. The Azotobacter consortia showed a potency for Hg bioremediation agent and biofertilizer due to the EPS and secondary metabolites production.