Effect of Cu2+ and Cd2+ on the growth and sulfidogenic activity of sulfate-reducing bacteria under using aromatic hydrocarbons

Abstract

Purification of the aquatic environment from substances of organic and inorganic matter is an urgent problem nowadays. Falling into the water of insufficiently treated effluents significantly impairs water quality and the condition of water bodies in general. Aromatic compounds, in particular toluene and xylene, are quite common pollutants in the aquatic environment. In addition to compounds of organic nature, wastewater contains many inorganic substances and heavy metal ions. Among the common methods of detoxification of the environment, biological ones play a leading role, as they are cost-effective and environmentally safe. One of the promising methods of purification is the usage of microorganisms, in particular sulfate-reducing bacteria. The influence of heavy metal ions on the accumulation of biomass and hydrogen sulfide by Desulfotomaculum sp. AR1 and D. desulfuricans Ya-11 bacteria during the growth in a medium with toluene and xylene is studied. The ability of sulfate-reducing bacteria Desulfotomaculum sp. AR1 and D. desulfuricans Ya-11 to grow with the simultaneous presence of aromatic compounds and heavy metal ions into the environment indicates their high potential in the usage to purify the aquatic environment from these contaminants. The inhibitory effect of metal ions on the process of reduction of sulfate ions by the studied bacteria, and, as a consequence, the accumulation of less toxic hydrogen sulfide, is shown. The influence of the source of carbon (sodium lactate/xylene/toluene) and heavy metal ions on the growth of bacteria Desulfotomaculum sp. AR1 and D. desulfuricans Ya-11 is analysed. It is shown that the accumulation of biomass by bacteria Desulfotomaculum sp. AR1 and D. desulfuricans Ya-11 are affected by both the nature of the electron donor and the presence of Cu2+ and/or Cd2+ ions in the medium. Penetrating into living cells, heavy metal ions disrupt their vital functions, but heavy metals are toxic only in the form of ions, but if they are translated into a bound form, they lose their toxic properties. The ability of the studied bacteria to precipitate Cu2+ and Cd2+ ions in the form of insoluble metal sulfides was revealed. Thus, the content of hydrogen sulfide in the aqueous medium can be adjusted, and in turn, it can be purified from heavy metal ions. According to the obtained results, sulfate-reducing bacteria Desulfotomaculum sp. AR1 and D. desulfuricans Ya-11 can be considered as promising in the development of methods for purification of the aquatic environment from heavy metal ions, in particular Cu2+ and Cd2+