Kinetics of arsenite oxidation by Sinorhizobium sp. M14 under changing environmental conditions

Many arsenite oxidizing bacteria show potential for application in bioremediation of arsenic-contaminated waters, but most can be used effectively only under conditions similar to those prevailing at their isolation site. This problem may be overcome by the use of the plasmid pSinA, which provides its hosts arsenite oxidation ability. However, the application potential of the natural host strain, Sinorhizobium sp. M14, has not been assessed under environmental conditions, which may readily affect the efficiency of the oxidation process. Thus, the aim of this study was to investigate the impact of several factors (e.g. pH, temperature, arsenic concentration) on the growth kinetics and arsenite oxidation abilities of Sinorhizobium sp. M14. Batch experiments were carried out to determine the adaptability of the strain. Subsequently, growth kinetics were tested and verified in continuous cultures, under environment-like conditions. The obtained results indicate that the strain is capable of intensive growth (doubling time = 9.2 h) and efficient biooxidation in a wide range of conditions, including low temperatures (As(III) oxidation rate = 0.533 mg L−1 h−1 at 10 °C). It was shown that aeration of the cultures may increase both growth and biooxidation rates, when appropriate supplementation with organic nutrients is provided. The obtained qualitative indicators allow for the comparison of arsenite-oxidizing abilities of M14 with other strains, proving its potential for application in arsenic-contaminated water treatment technologies.