Characterization of the Tunisian Phosphate Rock from Metlaoui-Gafsa Basin and Bio-Leaching Assays

Soil contamination by heavy metals through the application of a phosphate fertilizer is a key issue for sustainable agriculture. Among contaminants, cadmium (Cd) is considered the most hazardous to human beings’ health and the surrounding environment. X-ray diffraction (XRD), combined with binocular mineralogical analysis and chemical analysis, was used to determine the C(I) and C(II) layers’ composition. In the C(II) (+71 µm)-size fraction, the presence of carbonate-fluorapatite, illite, and montmorillonite was revealed, whereas in the C(I) (−71 µm)-size fraction, carbonate-fluorapatite, calcite, quartz, sanidine, clinoptilolite, and taramovite were identified. The P2O5 and CaO contents were greater in the C(II) layer than that in the C(I) layer, whereas SiO2, MgO, CO2, Cd, Zn, and COrg were higher in the C(I) layer than that in the C(II) layer. The bioleaching of Cd from phosphate rock samples from the Kef Eddour deposit was investigated using three bacterial strains isolated from the local phosphate environment. A decrease in cell viability was noticed when the phosphate C(I) and C(II) samples showed toxicity in the samples. In addition, the isolated bacteria, which were initially moderately hydrophobic, changed to strongly hydrophobic. The use of the consortium (S1 + S2 + S3) was the most powerful combination to reduce the Cd content, which increased from 13.31% to 29.07% using S3 and the consortium (S1 + S2 + S3), respectively, when the C(II) (+71 µm)-size fraction sample was added to the medium. The same result was shown when the C(I) (−71 µm)-size fraction sample was used. The isolated strains could be used as a biological tool for bioleaching

Isolation, characterization and identification of a new lysinibacillus fusiformis strain zc from metlaoui phosphate laundries wastewater: Bio-treatment assays

The aim of the present study is to isolate, characterize and identify a novel strain ZC from the Metlaoui phosphate laundries wastewater (MPLW). The chemical characterization of this phosphate rich effluent showed an alkaline pH and is saline, highly turbid and rich in suspended matter and total solids. The MPLW samples were loaded with potentially toxic metals, presented in decreasing order as follows: magnesium (5655 mg L), potassium (45 mg L), lead (1 mg L), iron (0.7 mg L), cadmium (0.5 mg L), copper (0.3 mg L) and zinc (0.1 mg L). Due to the high COD/BOD ratio, a poorly biodegradable organic load is underlining. The newly isolated strain was identified as Lysinibacillus fusiformis using 16S rDNA sequencing analysis. The viability of this new strain was tested in presence of the zinc, lead, cadmium, manganese and copper at 1, 10 and 100 mM. The L. fusiformis survival, under metallic stress, was inversely proportional to metal ion concentrations, while lead and zinc were the most toxic ones using MTT assay. Then, the newly isolated strain was characterized in terms of enzyme production, proteomic alteration and antibiotic resistance. The strain ZC revealed some modifications in the biochemical and enzymatic profiles by either the appearance or/and the disappearance of some activities. In addition, the increase in metal ions stress and concentrations was proportional to the adherence and to the hydrophobicity. The presence of the metal ions suggested the change of sensitivity to the resistance of this strain towards tobramycin, kanamycin, neomycin, netilmicin and cefoxitin, showing an increase in the MAR. The strain ZC, used as a biological tool for MPLW treatment, showed a reduction in the metal ion contents. This reduction was due to accumulation and/or adsorption, showing a bioprocessing performance of the newly isolated L. fusiformis