Biodegradation has been proven as the most efficient, eco-friendly and cost-effective technique for the removing of complex organic matters such as textile dyes from wastewater effluents. Some environmentally friend bacterial strains play an important role in such field. Acid red 337, an azo dye used extensively in textile industry, was reported as hazardous recalcitrant, when released into the aqueous environment. In the present research, a potential bacterial strain, capable of degrading acid red 337 (AR 337) dye was isolated from a textile wastewater effluent. Using 16S rRNA sequence analysis, the bacterium was identified as Bacillus megaterium KY848339.1. The decolorization capability of B. megaterium for AR 337 dye was optimized; the bacterium could remove 91% of dye concentration of 500 mg L −1 within 24 h when the inoculum size was 10% wt./v, solution pH was 7 and the incubation temperature was 30°C. The Liquid Chromatography-Mass Spectrum (LC-MS) analysis indicated the degradation of AR 337 azo dye by B. megaterium, to small aliphatic compounds and CO 2 . The application of B. megaterium on wastewater contaminated with red dyes using 10% wt./v of bacterial cells concentration was resulted in 98.9% removing of red color through 10 days.

In the twenty-first century, water contamination with pharmaceutical residues is becoming a global phenomenon and a threat. Antibiotic residues and antibiotic resistance genes (ARGs) are recognized as new emerging water pollutants because they can negatively affect aquatic ecosystems and human health, thereby posing a complex environmental problem. These nano-adsorbents of the next generation can remove these pollutants at low concentrations. This study focuses on the chemical synthesis of copper oxide nanoparticles (CuONPs) and nano-zero-valent iron (nZVI) used as nano-adsorbents for levofloxacin removal from water samples and antibiotic-resistant genes. The CuONPs and nZVI are initially characterized by transmission electron microscopy, scanning electron microscopy, and X-ray diffraction. The levofloxacin adsorption isotherm on the CuONPS and nZVI shows the best fit with the Langmuir isotherm model, exhibiting correlation coefficients (R2) of 0.993 and 0.999, respectively. The adsorption activities of CuONPS and nZVI were fitted to a pseudo-second-order kinetic model with correlation coefficients (R2) of 0.983 and 0.994, respectively. The maximum levofloxacin removal capacity was observed at (89%), (84%), (89%), (88%) and (71.6) at pH 7 and adsorbent dose(0.06 mg/L), initial LEV concentration (1 mg/L), temperature 25 °C, and contact time 120 min for CuONPs. Removal efficiency was (91%), (90.6%), (91%), (89%), and (80%), at pH 7, adsorbent dose(0.06), initial LEV concentration (1 mg/L), temperature 35 °C, and contact time 120 min. The levofloxacin adsorption is an exothermic process for nZVI and CuONPs, according to thermodynamic analysis. A thermodynamic analysis indicated that each adsorption process is spontaneous. Several genera, including clinically pathogenic bacteria (e.g., Acinetobacter_baumannii, Helicobacter_pylori, Escherichia_coli, Pseudomonas_aeruginosa, Clostridium_beijerinckii, Escherichia/Shigella_coli, Helicobacter_cetorum, Lactobacillus_gasseri, Bacillus_cereus, Deinococcus_radiodurans, Rhodobacter_sphaeroides, Propionibacterium_acnes, and Bacteroides_vulgatus) were relatively abundant in hospital wastewater. Furthermore, 37 antibiotic resistance genes (ARGs) were quantified in hospital wastewater. The results demonstrated that 95.01% of nZVI and 91.4% of CuONPs are effective adsorbents for removing antibiotic-resistant bacteria from hospital effluent. The synthesized nZVI and CuONPs have excellent reusability and can be considered cost effective and eco-friendly adsorbents. Graphical Abstract

High Nitrate concentration represented as one dangerous pollutant in the environment. Immobilization for the best denitrifying bacterial strain isolated from collected wastewater samples was suggested for bioremediation excessive nitrate concentration from aqueous solutions and explored its denitrification activity under different factors as (pH, nitrate concentration, bacterial beads, Temp and sodium alginate concentration). The active isolate was identified as Pseudomonas putida MT364822.1 by 16S rRNA analysis. Nitrate bioremediation process was optimized by apply response surface method based on central composite design approach. Nitrate uptake was significantly affected by variables of study (p-value <0.05). Maximum removal of nitrate 91.1% was obtained from pH 7, nitrate concentration 400 mg/L, immobilized bacterial beads 3.0 g/L, Temp 35 °C and sodium alginate concentration 2.5% as optimal variable values. For application, immobilized Pseudomonas putida MT364822.1 removed nitrate with 82.2% from raw fish farm effluent. Storage and reusability experiments showed the strength and stability of immobilized strain more than pure. The results suggested that, immobilized Pseudomonas putida MT364822.1 is a highly promising and suitable microorganism to be used in bio-removal of nitrate and central composite design was more effective in optimization variables to obtain the highest nitrate removal efficiency.

The examination of the performance of raw and immobilized S. (Saccharomyces) cerevisiae in the simultaneous abatement of metal ions from wastewater effluent is the focal point of this article. The optimal storage time for raw and immobilized S. cerevisiae, during which they can be utilized, was estimated. The outcomes revealed that as the initial metal ion concentrations increased, the adsorption capacity improved, while the removal efficiency of S. cerevisiae yeast cells decreased, with the highest uptake obtained at the optimal conditions: pH = 5.0, 2.0 g S. cerevisiae/L, 25 °C, and a contact time of 25 min. The maximum adsorption capacities (qmax) for Pb(II), Cd(II), and Ni(II) ions are shown by Langmuir at 65, 90, and 51 mg/g, respectively. It was discovered that the metal ions’ biosorption reactions were spontaneous and were fitted by the pseudo-second-order model. The mechanisms of the metal ions’ abatement were explained by using XRD (X-ray diffraction), FTIR (Fourier transform infrared spectroscopy), (BET) Brunauer–Emmett–Teller, and TEM (transmission electron microscopy) outputs. EDTA and citric acid can eliminate more than 70 ± 4 and 90 ± 5% of the adsorbed ions, respectively. The experiment of storage demonstrated that the immobilized S. cerevisiae was more stable for 8 months than the raw yeast.

The emergence of antibiotic resistance is considered a major threat, and this problem is exacerbated due to the excessive use of antibiotics. Therefore, it is necessary to find new antimicrobials that are effective against pathogenic bacteria resistant to existing antimicrobials. This study presents a novel antimicrobial approach for the bio-control of multi-antibiotic-resistant (MAR) bacteria. Ten antibiotic discs were used to evaluate the bacterial sensitivity. Five bacterial strains showed resistance to all the tested antibiotic groups. The following MAR bacterial strains were selected, and their identification was confirmed by 16S rRNA with an accession number on the NCBI: Shigella flexneri MZ350855.1; Klebsiella aerogenes MZ352107.1; Serratia marcescens MZ618709.1; Yersinia enterocolitica MZ673567.1; Achromobacter denitrificans OK560350.1. Star anise extract (SAE) gives the highest inhibitory efficiency against isolated MAR bacteria between three local plant extracts. SAE was used to synthesize magnetite nanoparticles (MNPs) using a simple and eco-friendly green biosynthesis technique. Synthesized MNPs were characterized by X-ray diffraction, ultraviolet–visible spectroscopy, Fourier transform infrared, and transmission electron microscopy techniques. The effect of synthesized magnetic nanoparticles for wastewater treatment in bacterial portion demonstrated remarkable bactericidal performance against total bacterial count with a percentage reduction of 84% using 0.05 g, and the efficiency of decreasing heavy metals was estimated.