Biosorption of Heavy Metals onto Different Eco-Friendly Substrates

Abstract

Aims and BackgroundThe basic environmental elements constituting ecosystem is the soil, which is the important material basis of human being to survive and develop. The contaminated soil by heavy metals manifests as concealment, accumulation, irreversibility and protraction. To prevent the heavy metal contamination, sources of contamination should be controlled and remediation of contaminated soils should be enhanced [1]. Recently, decreasing the amount of pollutants and improving the quality of the treated soils have been studied for the development of cheaper and more effective remediation technique. One of the most alternative treatments is adsorption. The adsorbents may be of mineral, organic or biological origin, zeolites, industrial byproducts, agricultural wastes, biomass, and polymeric materials [2]. Microorganisms (bacteria, fungi and algae) are effective heavy metal sequestration for physicochemical methods [3][4][5][6][7]. Removal of potentially toxic metals from polluted industrial and domestic effluents have already been used in large scale using certain microorganisms. These microorganisms have been shown to possess an ability to survive by adapting or mutating at high concentrations of toxic heavy metals. To increase the tolerance of fungi for the bioleaching process, the adaptation of these fungi exposed to heavy metal ions has been examined and developed [8].Generally, two mechanisms have been proposed for heavy metal tolerance in fungi. The first one is an extracellular (chelation and cellwall binding) sequestration and the second is intracellular physical sequestration of metal by binding to proteins or other ligands to prevent it from damaging the metal sensitive cellular targets. Thus, extracellular mechanisms are mainly implied in the avoidance of metal entry, whereas intracellular systems aim to reduce the metal burden in the cytosol. In the first mechanism, different organic molecules that do not belong to the matrix of the cell wall are excreted by the fungal cell to chelate metal ions. Binding to the cell wall is called biosorption. The presence of various anionic structures, such as glucan and chitin gives negatively charged to the cell surface of microorganisms [9,10], which gives microorganisms the ability to bind metal cations. In the intracellular mechanism, metal transport proteins may be involved in metal tolerance, either by extruding toxic metal ions from the cytosol out of the cell or by allowing metal sequestration into vacuolar compartment [11,12]. Biosorption of Heavy Metals onto Different Eco-Friendly Substrates AbstractFungi play an important role in biosorption of heavy metals in heavily contaminated soils. Five metals-tolerant fungal species were isolated from two different contaminated soils (soil 1 and soil 2). The number of fungal colonies isolated from the contaminated soil 2 was higher than that of soil 1. The most resistant fungal species for the toxic studied metals (Pb, Cd, Cu and Zn) was Rhizopus stolonifier followed by Macrophomina phaseolina. It was establi...

Bioremoval of Different Heavy Metals by the Resistant Fungal StrainAspergillus niger

“…The removal of heavy metal ions, using fungus as biosorbents, was previously investigated [ 2 , 4 , 12 , 17 – 20 ]. Our results confirm the capacity of the microorganisms biomass for the removal of heavy metals with different effectivity, like bacteria, fungus, yeast, and algae-based microbiological decontamination of heavy metals contaminated soils of different places [ 2 – 5 ]: M. phaseolina and R. stolonifer for the removal of lead, cadmium, copper, and zinc, from soil [ 11 ], the removal of lead, cadmium, and chromium, in liquid culture with P. ostreatus HAAS [ 12 ], the removal of lead, cadmium, copper, and nickel, with A. niger [ 19 ], the elimination of copper, cadmium, lead, and zinc in dried soil residues with A. niger during the bioleaching process [ 12 ], the removal of copper (II) and cadmium (II) in batch systems by immobilized cells of A. niger [ 20 ], the removal of 90% of chromium (VI) by NaOH-pretreated A. niger biomass, and that heavy metal uptake by live A. niger biomass for cadmium (II) and for zinc (II) [ 29 ], yeasts isolated from water, soil, and plant environments [ 30 ], and other studies with other species of fungi [ 4 , 18 , 19 , 31 – 34 ]. According to our results, we can assume the surface of the biomass coated with iron oxide is partially ionized, causing the pH to approach neutrality; apparently, the OH − groups present compete for the binding sites with the heavy metals and the biomass, decreasing the removal of metals, while at acid pH, there is a better removal of the heavy metals [ 35 ].…”

“…Different microorganisms that are heavy metals resistant have been isolated from different contaminated sites: screening the resistance to lead, cadmium, copper, and zinc of five fungal species isolated from soils: Emericella quadrilineata , A. niger , Macrophomina phaseolina , R. stolonifer , and Aspergillus fumigatus , and the most resistant fungal species (1 g/L of metals) was R. stolonifer followed by M. phaseolina which showed resistance with all the metals, while A. niger, A. fumigatus , and E. quadrilineata were more sensitive to these heavy metals [ 11 ], the fungus P. ostreatus HAAS grew very well in 500 mg/L of lead, and concentrations of 30 mg/L of cadmium and 200 mg/L of chromium appeared to inhibit the growth of the fungus [ 12 ], B. megaterium strain MNSH1-9K-1 tolerate up to 200 ppm of each nickel and vanadium [ 13 ], Alcaligenes sp. BAPb.1, grow in the presence of 1000 mg/L of lead (II), 600 mg/L of copper (II), 600 mg/L of zinc (II), 400 mg/L of nickel (II) and chromium(VI) [ 15 ], Penicillium sp., Trichoderma sp., and Alternaria sp., isolated from the farmland of the “Tanque Tenorio”, grow with 500–2000 mg/L of lead (II) [ 16 ], A. niger has been growing in the presence of different concentrations of metals like nickel, cobalt, iron, magnesium, and manganese [ 27 ], and the yeast Candida tropicalis , isolated from wastewater from industrial area of Sheikhupura, which is grown in 2.5 g/L of cadmium (II), zinc (II) (1.4 g/L), nickel (II) (1 g/L), Mercury (II) (1.4 g/L), copper (II) (1 g/L), chromium (VI) (1.2 g/L), and lead (II) (1 g/L) [ 28 ].…”

“…Dead fungal cells can be effective metal accumulators, and there is evidence that some biomass-based cleanup processes are economically viable [ 2 , 4 ]. The tolerance of some fungal species to heavy metals, as well as the physiological response to them, has been also determined [ 2 , 11 – 13 ]. The removal of heavy metal ions, using fungus as biosorbents, was previously investigated [ 2 , 4 , 12 , 17 – 20 ].…”

“…The foregoing, together with the waste from mining, aggravates the situation of the contamination by heavy metals in Mexico. Different public institutions have developed investigations to establish the magnitude of this problem and have proposed strategies to contribute to the solution of the same, focusing on the use of biological alternatives that result in a lower alteration of the environment, specifically through the use of microorganisms for the removal of heavy metals or biosorption [ 11 ]. There are many reports of the isolation of resistant microorganisms to heavy metals and the use of microbial biomass for the removal of heavy metals, from industrial wastewater and/or contaminated water: the resistance and removal of Rhizopus stolonifer to lead, cadmium, copper, and zinc [ 11 ], the tolerance and removal mechanisms of heavy metals (lead, cadmium, and chromium), by the fungus Pleurotus ostreatus HAAS [ 12 ], Bacillus megaterium nickel resistance and her capacity of removal [ 13 ], heavy metal susceptibility and removal potential (mercury, copper, and lead) of Rhodotorula mucilaginosa [ 14 ], the resistance of Alcaligenes sp.…”

“…Different public institutions have developed investigations to establish the magnitude of this problem and have proposed strategies to contribute to the solution of the same, focusing on the use of biological alternatives that result in a lower alteration of the environment, specifically through the use of microorganisms for the removal of heavy metals or biosorption [ 11 ]. There are many reports of the isolation of resistant microorganisms to heavy metals and the use of microbial biomass for the removal of heavy metals, from industrial wastewater and/or contaminated water: the resistance and removal of Rhizopus stolonifer to lead, cadmium, copper, and zinc [ 11 ], the tolerance and removal mechanisms of heavy metals (lead, cadmium, and chromium), by the fungus Pleurotus ostreatus HAAS [ 12 ], Bacillus megaterium nickel resistance and her capacity of removal [ 13 ], heavy metal susceptibility and removal potential (mercury, copper, and lead) of Rhodotorula mucilaginosa [ 14 ], the resistance of Alcaligenes sp. BAPb.1 to lead (II), copper (II), zinc (II), nickel (II), and chromium (VI), and his capacity for removal of lead (II) [ 15 ], the isolation and identification of fungi and yeast resistant to lead (II) [ 16 ], the resistance and removal of chromium (VI) by Aspergillus niger [ 17 ], the removal of different heavy metals by A. niger [ 18 ], the removal of lead, cadmium, copper, and nickel by A. niger [ 19 ], the removal of aluminum, iron, lead, and zinc by A. niger during the bioleaching process [ 12 ], and the removal of copper (II), manganese (II), zinc (II), nickel (II), iron (III), lead (II), and cadmium (II) by immobilized cells of A. niger [ 20 ], with highly satisfactory results.…”