Tolerance of Chemoorganotrophic Bioleaching Microorganisms to Heavy Metal and Alkaline Stresses

Abstract

The bioleaching potential of the bacterium Bacillus mucilaginosus and the fungus Aspergillus niger towards industrial residues was investigated by assessing their response towards various heavy metals (including arsenic, cadmium, cobalt, chromium, nickel, lead, and zinc) and elevated pH. The plate diffusion method was performed for each metal to determine the toxicity effect. Liquid batch cultures were set up for more quantitative evaluation as well as for studying the influence of basicity. Growth curves were prepared using bacterial/fungal growth counting techniques such as plate counting, optical density measurement, and dry biomass determination. Cadmium, nickel, and arsenite had a negative influence on the growth of B. mucilaginosus, whereas A. niger was sensitive to cadmium and arsenate. However, it was shown that growth recovered when microorganisms cultured in the presence of these metals were inoculated onto metal-free medium. Based on the findings of the bacteriostatic/fungistatic effect of the metals and the adaptability of the microorganisms to fairly elevated pH values, it is concluded that both strains have potential applicability for further research concerning bioleaching of alkaline waste materials.

Considerations about recovery of critical metals using bio-metallurgy

“…As primary resources become scarcer enhanced landfill mining will become more feasible. However, strategic policy decisions and tailored support systems for enhanced landfill mining is sustained by standardized life cycle assessment frameworks and will be indispensable to remove the remaining non-technical barriers [37].…”

“…The optimal growth conditions for microorganisms must be maintained in order to assure the resistance of microbes to the metals and get a good efficiency of bioprocesses. [37].…”

Effect of Vitamin C on Cadmium Depending Growth and Vitamin C Contents of Citrobacter Freundii

“…In the study conducted by Yiğit et al (2013) it was reported that the growth rate of Lactobacillus brevis started to decrease more than 35 ppm cadmium. It has been demonstrated that 100 ppm cadmium concentration has a negative effect on the growth of B. mucilaginosus and A. niger microorganisms (Monballiu et al 2015). The decrease in microorganism concentration may be due to the toxic effect of cadmium in the cell, which effects many metabolic activities including protein synthesis (Çınar, 2003).…”

Kadmiyumla stres oluşturulan Citrobacter freundii’nin vitamin içeriği ve stres belirteçlerine selenyumun etkisi

“…Farklı derişimlerdeki kadmiyum ve selenyum içeren besi yerinde üretilen C. freundii konsantrasyonu Yiğit ve arkadaşları [15] tarafından yapılan çalışmada 35 ppm'den yüksek kadmiyum konsantrasyonlarında Lactobacillus Brevis'in büyüme hızının azaldığını rapor edilmiştir. 100 ppm kadmiyum konsantrasyonunun B. mucilaginosus ve A. niger mikroorganizmalarının büyümesini olumsuz etkilediği gösterilmiştir [16]. Mikroorganizma konsantrasyonundaki azalma, protein sentezi dâhil birçok metabolik aktiviteyi etkileyen hücredeki kadmiyumun toksik etkisinden kaynaklanıyor olabilir [17].…”