Isolation, Characterization and Identification of a New Lysinibacillus fusiformis Strain ZC from Metlaoui Phosphate Laundries Wastewater: Bio-Treatment Assays

Abstract

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−1), potassium (45 mg L−1), lead (1 mg L−1), iron (0.7 mg L−1), cadmium (0.5 mg L−1), copper (0.3 mg L−1) and zinc (0.1 mg L−1). Due to the high COD/BOD5 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 MARindex. 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.

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

“…In this study, three strains (S1, S2, and S3) were isolated using Luria Bertani (LB) medium supplemented with the autoclaved effluent (100%) from Metlaoui phosphate laundries discharged in Oued sakdoud, Gafsa Governorate, South-West of Tunisia (north latitude 34 • 20 , east longitude 8 • 22 ). The strain S3 was identified as Lysinibacillus fusiformis strain ZC (ID: KX148607) [13]. The isolated strains were inoculated on LB broth (LB).…”

“…A cell viability essay was performed using a colorimetric essay from yellow to violet [13]. The reduction of tetrazolium salt (MTT) to soluble formazon salt water was the result of the metabolically active cells.…”

“…The reduction of tetrazolium salt (MTT) to soluble formazon salt water was the result of the metabolically active cells. The experimental protocol was carried out as described by Taieb et al (2021) [13]. Finally, the produced solubilized formazon was quantified by photometry at 570 nm.…”

“…It has been shown to be an efficient, sustainable, and cost-effective method that allows Cd to be eliminated without generating new pollution [6,12]. Recently, the removal of environmental toxic waste via biological agents, named bioremediation, has become an innovative, effective tool that could be the key to addressing this problem [6,13]. Microorganisms deploy many mechanisms for their survival in and resistance to metallic environments, including metal oxidation, methylation, enzymatic degradation, metalorganic complexion, decreasing the metal concentration, metal-ligand degradation, metal efflux pumps, demethylation, intracellular and extracellular metal sequestration, exclusion by a permeability barrier, and production of metal chelators such as metallothioneins and biosurfactants.…”

“…Microorganisms deploy many mechanisms for their survival in and resistance to metallic environments, including metal oxidation, methylation, enzymatic degradation, metalorganic complexion, decreasing the metal concentration, metal-ligand degradation, metal efflux pumps, demethylation, intracellular and extracellular metal sequestration, exclusion by a permeability barrier, and production of metal chelators such as metallothioneins and biosurfactants. For example, to eliminate metallic contaminants, microorganisms can utilize valence conversion, volatilization, or extracellular chemical precipitation [13].…”