Rafael Osok

• Biodiversity Journal, 8 (1): 021-026

  Reginawanti Hindersah, Oviyanti Mulyani & Rafael Osok
  Proliferation and exopolysaccharide production of Azotobacter in the presence of mercury

  ABSTRACT
  Bioremediation is a cheap, easy and effective method to improve the quality of heavy metal-contaminated agricultural land. Plant Growth Promoting Rhizobacteria recently has been proposed to be used in bioremediation of heavy metal. Rhizosphere-inhabitant Azotobacter produce exopolysaccharide (EPS) as a mechanism to avoid heavy metal poisoning; and in other hand EPS mobilize heavy metals in soil. The objective of this study was to get an information about growth and exopolysaccharide production profile of Azotobacter in media with and without mercury chloride. The bacteria were isolated from mercury-contaminated tailing at gold mining area in Maluku Province; and cultured in liquid medium containing 5, 10, 15 and 20 mg/L of HgCl₂. Cultures were incubated for 4 days at 115 rpm on gyratory shaker at room temperature. The results showed that all three isolates of Azotobacter enabled to grow in media with lower level of HgCl₂ but Azotobacter Buru-1 and Buru-2 did not grow on media with 20 mg/L of HgCl₂. Azotobacter bd3a was able to grow on media with 20 mg/L of HgCl₂ although the cell density was lower than that of control and lower level of mercury. The presence of mercury affected and generally suppressed the production of EPS; but the effect depend on the isolates. Azotobacter Buru-2 produced more EPS at 2 and 4 days after incubation in the presence of 20 mg/L of HgCl₂.

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