Resistance and bioaccumulation of Cd2+, Cu2+, Co2+ and Mn2+ by thermophilic bacteria, Geobacillus thermantarcticus and Anoxybacillus amylolyticus

The genus Anoxybacillus: an emerging and versatile source of valuable biotechnological products

Thermophilic and alkaliphilic microorganisms are unique organisms that possess remarkable survival strategies, enabling them to thrive on a diverse range of substrates. Anoxybacillus, a genus of thermophilic and alkaliphilic bacteria, encompasses 24 species and 2 subspecies. In recent years, extensive research has unveiled the diverse array of thermostable enzymes within this relatively new genus, holding significant potential for industrial and environmental applications. The biomass of Anoxybacillus has demonstrated promising results in bioremediation techniques, while the recently discovered metabolites have exhibited potential in medicinal experiments. This review aims to provide an overview of the key experimental findings related to the biotechnological applications utilizing bacteria from the Anoxybacillus genus.

The removal of heavy metal pollution from wastewaters using thermophilic B. cereus SO-16 bacteria

In this study, bioaccumulation, remediation, tolerance, and effects of manganese ions (Mn(II)) and copper ions (Cu(II)) on antioxidant enzymes of thermophilic Bacillus cereus (B. cereus) SO-16 were investigated in detail. The findings of the study showed that Mn(II) was less toxic than Cu(II) to B. cereus SO-16. Moreover, B. cereus SO-16 was exhibited less tolerance to Mn(II) and Cu(II) ions in the liquid medium compared to the solid medium. The growth of bacteria was expressively effective for Mn(II) and Cu(II) concentrations of 2.5 mg/L at 24th h. The highest Mn(II) and Cu(II) bioaccumulation values after 48 h incubation of thermophilic B. cereus SO-16 were measured as 102.04 (24th h) and 87.96 (36th h) metal/dry bacteria weight. The change in morphology and functionality of B. cereus SO-16 after interaction with Mn(II) and Cu(II) was tested using various methods. The results indicated that B. cereus SO-16, a thermophilic bacterium, can be utilized in industrial wastewaters to recover and remediation of toxic metals.

Manganese Pollution and Its Remediation: A Review of Biological Removal and Promising Combination Strategies

Manganese (Mn), as a cofactor of multiple enzymes, exhibits great significance to the human body, plants and animals. It is also a critical raw material and alloying element. However, extensive employment for industrial purposes leads to its excessive emission into the environment and turns into a significant threat to the ecosystem and public health. This review firstly introduces the essentiality, toxicity and regulation of Mn. Several traditional physicochemical methods and their problems are briefly discussed as well. Biological remediation, especially microorganism-mediated strategies, is a potential alternative for remediating Mn-polluted environments in a cost-efficient and eco-friendly manner. Among them, microbially induced carbonate precipitation (MICP), biosorption, bioaccumulation, bio-oxidation are discussed in detail, including their mechanisms, pivotal influencing factors along with strengths and limitations. In order to promote bioremediation efficiency, the combination of different techniques is preferable, and their research progress is also summarized. Finally, we propose the future directions of Mn bioremediation by microbes. Conclusively, this review provides a scientific basis for the microbial remediation performance for Mn pollution and guides the development of a comprehensive competent strategy towards practical Mn remediation.

Potential application of thermophilic bacterium Aeribacillus pallidus MRP280 for lead removal from aqueous solution

Bacteria used for application of lead (Pb) removal is usually kept under suboptimal growth conditions. Certain application of Pb removal may be carried out under different condition, such as under aqueous and high temperature conditions. It is, therefore, of interest to examine the Pb removal capacity of the bacteria under adverse environmental conditions. In the present study, Aeribacillus pallidus MRP280, a lead-tolerant thermophilic bacterium was used as an absorbent for the removal of Pb from aqueous solution. The Pb removal and uptake capacity of living and non-living bacterial cells of A. pallidus MRP280 was investigated in 100 mg/L Pb solution. The optimum condition was examined based on several analytical parameters, including temperature, pH, contact time, and cell density. Biosorbent analysis and characterization was carried out using Fourier Transform Infrared (FT-IR) spectroscopy, Scanning Electron Microscope (SEM)-Energy Dispersive X-ray (EDX), and Transmission Electron Microscope (TEM). The results showed that the maximum Pb removal of 96.78 ± 0.19% and 88.64 ± 0.60% were obtained using living and non-living biomass, respectively at 55 °C, pH 6, OD₆₀₀0.5 for 100 min. Meanwhile, the maximum uptake capacity of 86.47 ± 1.32 mg/g and 85.31 ± 1.37 mg/g by living and non-living cells was reached at 55 °C, pH 6, OD₆₀₀0.25 for 60 min. Moreover, Pb removing activity was facilitated by the biosorption and bioaccumulation process. Overall, it is shown that A. pallidus MRP280 is effective when applied as biosorbent in removing Pb from contaminated wastewater at high temperatures.

Resistance, bioaccumulation and solid phase extraction of uranium (VI) by Bacillus vallismortis and its UV-vis spectrophotometric determination

Bioaccumulation, resistance and preconcentration of uranium(VI) by thermotolerant Bacillus vallismortis were investigated in details. The minimum inhibition concentration of (MIC) value of U(VI) was found as 85 mg/L and 15 mg/L in liquid and solid medium, respectively. Furthermore, the effect of various U(VI) concentrations on the growth of bacteria and bioaccumulation on B. vallismortis was examined in the liquid culture media. The growth was not significantly affected in the presence of 1.0, 2.5 and 5.0 mg/L U(VI) up to 72 h. The highest bioaccumulation value at 1 mg/L U(VI) concentration was detected at the 72nd hour (10 mg/g metal/dry bacteria), while the maximum bioaccumulation value at 5 mg/L U(VI) concentration was determined at the 48th hour (50 mg metal/dry bacteria). In addition to these, various concentration of U(VI) on α-amylase production was studied. The α-amylase activities at 0, 1, 2.5 and 5 mg/L U(VI) were found as 3313.2, 3845.2, 3687.1 and 3060.8 U/mg, respectively at 48th. Besides, uranium (VI) ions were preconcentrated with immobilized B. vallismortis onto multiwalled carbon nanotube (MWCNT) and were determined by UV-vis spectrophotometry. The surface macro structure and functionalities of B. vallismortis immobilized onto multiwalled carbon nanotube with and without U(VI) were examined by FT-IR and SEM. The optimum pH and flow rate for the biosorption of U(VI) were 4.0-5.0 and 1.0 mL/min, respectively. The quantitative elution occurred with 5.0 mL of 1 mol/L HCl. The loading capacity of immobilized B. vallismortis was determined as 23.6 mg/g. The certified reference sample was employed for the validation of developed solid phase extraction method. The new validated method was applied to the determination of U(VI) in water samples from Van Lake-Turkey.