Remediation of cyanide from the gold mine tailing pond by a novel bacterial co-culture

•Simultaneously application of two bacteria enhances the remediation of cyanide rate.•Both cyanide consuming strains were reported for the first time.•Exact cyanide bioremediation versus volatilization was calculated by BRE equation.

A total of 310 isolates were obtained from the gold mine tailing pond, in Khorasan-Razavi province in NE Iran. The cyanide tolerances of these strains were studied in an M9 medium supplemented by different cyanide concentrations. Nine strains showed the highest level of cyanide tolerance and could grow in up to 350 ppm of cyanide. Of these, two isolates, designated BN1 (identified as Halomonas to genus level by 16SrDNA sequencing) and DNB, capable of metabolizing cyanide as the sole source of nitrogen were selected for further analysis. The effects of different factors including pH, temperature, inoculum size and initial cyanide concentration were studied on the remediation process by OFAT (one factor at a time) experimental design. Strains BN1 and DNB showed 66% and 50% removal of cyanide at pH 9.5, temperature 25 °C, inoculum size 2.5% (v/v) and an initial cyanide concentration of 50 ppm after five days, respectively. The co-culture of strains was removed 75% of cyanide from the tailing pond after 96 h.