Impacts of different concentrations of Copper and Zinc on in vitro responses of Azotobacter chroococum in biomass and nitrogen fixing outputs

The responses of Azotobacter chroococum for copper and zinc were surveyed in this study. The impacts of different concentrations of copper and zinc on biomass formation and nitrogen fixation of Azotobacter chroococum were investigated. Batch trials were performed under continuous airflow using Jensen’s nitrogen free broth, at ambient room temperatures for seven days. Maximum biomass yields of 0.068 OD600 units and 0.131 OD600 units were recorded at 25 mg L -1 and 200 mg L-1 for copper and zinc amended trials, respectively. Maximum nitrogen fixations of 1.446 ppm and 1.507 ppm were also recorded for copper and zinc amended trials at 12.5 mg L-1, respectively. Statistical analysis revealed strong significant correlations between metal concentrations and nitrogen fixation for copper and zinc amended trials, respectively. Leudeking-Piret modeling showed that nitrogen fixations of Azotobacter chroococum in both copper and zinc amended trials were associated with biomass density.