Biosorption of copper by immobilized biomass of Aspergillus australensis. Effect of metal on the viability, cellular components, polyhydroxyalkanoates production, and oxidative stress

Heavy metals are toxic especially when they are introduced into the environment due to anthropogenic activities such as metallurgy, mining, and tanning. Removing these pollutants has become a worldwide concern since they cannot be degraded into nontoxic forms causing extended effects in the ecosystems. The use of an Aspergillus australensis was evaluated in order to remove Cu2+ from simulated wastewater. The fungus was isolated from river sludges contaminated with heavy metals and was first evaluated for the determination of Cu2+ tolerance levels. Microscopic fluorescence analysis was carried out to determine the effect of Cu2+ presence on the viability, cellular components, polyhydroxyalkanoates production, and oxidative stress of the fungus, as a response to the stress caused by exposure to metal. In order to achieve copper removal, the A. australensis biomass was produced using batch cultures, and the mycelium was immobilized on a textile media in order to compare the copper-removal efficiency of live or dead biomass. The optimal values of pH and temperature for biomass production were established by using a surface response analysis. Live immobilized biomass was capable of removing Cu2+ from 1.54 +/- 0.19 to 2.66 +/- 0.26 mg of copper/ g of dry biomass, while values of 1.93 +/- 0.03 to 2.36 +/- 0.29 mg of copper/g of dry biomass were observed when dead biomass was used. As was expected, copper removal using biomass varied depending on the pH and temperature used.