Arsenic tolerance of Microcystis novacekii (Komárek-Compère, 1974) and its arsenic decontamination potential

Abstract

Cyanobacteria possess metallic ion interaction properties that should be explored with the aim of recovering arsenic (As) contaminated areas. Contamination of As is an issue of worldwide concern due to the risk of human chronic intoxication and negative environmental health effects. In this study the potential decontamination of As (III) and As(V) using cyanobacteria cultures was assessed. Microcystis novacekii (Komárek-Compere, 1974) showed normal growth in concentrations of As(V) similar to those found in natural environments contaminated with As, demonstrating its resistance to As(V). Growth rates gradually decreased upon exposure to high As(V) concentrations from 600 to 5630 mg.L -1 while As(III) affected growth from 14.7 -85.7 mg.L -1 . The As(III) EC50 value (41.0 mg.L -1 ) was 140-fold lower possibly due to differences in As(III) and As(V) absorption pathways. Upon exposure to 14.7 mg.L -1 As(III), 21.2% of As was removed from culture medium. The absorption capacity (12000 mg.kg -1 ) remained constant with increasing As(III) concentrations in a dose independent effect. The potential of M. novacekii for As decontamination was demonstrated in this study. This microorganism is recommended in As bioremoval studies due to its autotrophicmixotrophic growth, low nutritional requirements and high As(III) absorption capacity. Biological and Applied SciencesFerreira, FAG et al.Braz. Arch. Biol. Technol. v.61: e18160644 2018 . The risk of As exposure is an issue of worldwide concern 1, 4 . Chronic intoxication by this element has been reported in several countries (e. g. Bangladesh, Vietnam, China, Argentina, Chile) where As in water exceeds safety limits in some localities 5, 6, 7 . On the aquatic ecosystem As pollution can affect the equilibrium and coexistence of aquatic organisms. Furthermore, the capacity of As accumulation by aquatic primary producers is determinant for its biomagnification in the trophic chain 8 . Using microorganisms as a tool for removal of contaminants such as metals and metalloids is a low-cost process known as bioremediation 9 . Bioremediation technologies have a promising potential to contribute eco-friendly manner. These comprise high-efficiency techniques for heave metal removal in from dilute solutions, in addition, they could provide metal recovery 10 . The accumulation and concentration of pollutants from aqueous solutions by the use of biological materials [such as aquatic macrophytes biomass 11,12,13 or microbial biomass 14,15,16 ], facilitating the recovery and/or environmentally acceptable disposal of the pollutant is termed as "bioremoval" 17 . The possibility of using clean technologies for environmental decontamination has spurred the search for resistant organisms that are capable of biotransforming toxic elements such as As. The possibility of using clean technologies for environmental decontamination has spurred the search for resistant organisms that are capable of biotransforming toxic elements such as As 18 . Arsenic metabolism by cyanobacteria has mainly been studi...