Enhanced biodegradation of ciprofloxacin by enrich nitrifying sludge: assessment of removal pathways and microbial responses

Antibiotics are mostly collected by sewage systems, but not completely removed within wastewater treatment plants. Their release to aquatic environment poses great threat to public health. This study evaluated the removal of a widely used fluoroquinolone antibiotic ciprofloxacin in enriched nitrifying culture through a series of experiments by controlling ammonium concentrations and inhibiting functional microorganisms. The removal efficiency of ciprofloxacin at an initial concentration of 50 μg L−1 reached 81.86 ± 3.21% in the presence of ammonium, while only 22.83 ± 8.22% of ciprofloxacin was removed in its absence. The positive linear correlation was found between the ammonia oxidation rate (AOR) and ciprofloxacin biodegradation rate. These jointly confirmed the importance of the AOB-induced cometabolism in ciprofloxacin biodegradation with adsorption and metabolic degradation pathways playing minor roles. The continuous exposure of AOB to ciprofloxacin led to decreases of ammonia monooxygenase (AMO) activities and AOR. The antibacterial effects of ciprofloxacin and its biodegradation products were further evaluated and the results revealed that biodegradation products of ciprofloxacin exhibited less toxicity compared to the parent compound, implying the potential application of cometabolism in alleviation of antimicrobial activity. The findings provided new insights into the AOB-induced cometabolic biodegradation of fluoroquinolone antibiotics.

Chemically Enhanced Biodegradation of High Organic Matter in Wastewater – Confectionary Plant Effluents

The study explored the merit of chemically enhanced biodegradation of high organic matter as a sustainable treatment scheme for industrial wastewaters. For this purpose, an integrated, chemically enhanced activated sludge configuration was tested for confectionary effluents with a COD level of around 10.000 mg L-1. In this configuration, chemical settling acted as a polishing step, which removed 50% of the total COD load, including 10% of colloidal COD in the soluble COD range. The sequential batch reactor, selected as the final biological treatment step, was able to remove the remaining biodegradable COD completely. The study primarily demonstrated the merit of in-plant pollution footprint assessment and wastewater characterization with significant COD fractions as necessary prerequisites for the management and final biodegradation of industrial wastewaters with high organic matter content.

Insights Into Mechanism of the Naphthalene-Enhanced Biodegradation of Phenanthrene by Pseudomonas sp. SL-6 Based on Omics Analysis

The existence of polycyclic aromatic hydrocarbons (PAHs) in contaminated environment is multifarious. At present, studies of metabolic regulation focus on the degradation process of single PAH. The global metabolic regulatory mechanisms of microorganisms facing coexisting PAHs are poorly understood, which is the major bottleneck for efficient bioremediation of PAHs pollution. Naphthalene (NAP) significantly enhanced the biodegradation of phenanthrene (PHE) by Pseudomonas sp. SL-6. To explore the underlying mechanism, isobaric tags for relative and absolute quantification (iTRAQ) labeled quantitative proteomics was used to characterize the differentially expressed proteins of SL-6 cultured with PHE or NAP + PHE as carbon source. Through joint analysis of proteome and genome, unique proteins were identified and quantified. The up-regulated proteins mainly concentrated in PAH catabolism, Transporters and Electron transfer carriers. In the process, the regulator NahR, activated by salicylate (intermediate of NAP-biodegradation), up-regulates degradation enzymes (NahABCDE and SalABCDEFGH), which enhances the biodegradation of PHE and accumulation of toxic intermediate–1-hydroxy-2-naphthoic acid (1H2Na); 1H2Na stimulates the expression of ABC transporter, which maintains intracellular physiological activity by excreting 1H2Na; the up-regulation of cytochrome C promotes the above process running smoothly. Salicylate works as a trigger that stimulates cell to respond globally. The conjecture was verified at transcriptional and metabolic levels. These new insights contribute to improving the overall understanding of PAHs-biodegradation processes under complex natural conditions, and promoting the application of microbial remediation technology for PAHs pollution.

Polylactic Acid Cellulose Nanocomposite Films Comprised of Wood and Tunicate CNCs Modified with Tannic Acid and Octadecylamine

Herein, a one-pot strategy was used to prepare hydrophobic cellulose nanocrystals (CNCs) surface-modified with tannic acid and octadecylamine. By this strategy, CNCs derived from wood (W-CNC) and tunicates (T-CNC) were modified in situ and incorporated into a polylactic acid (PLA) matrix using two methods, without first drying the CNCs. Films of PLA-CNC nanocomposites were prepared both by solution casting and by wet compounding in a thermo-kinetic mixer, followed by melt extrusion. Various properties of these PLA nanocomposites were evaluated herein, along with an assessment of how these properties vary with the type of CNC reinforcement. Cast films with a hybrid mixture of wood and tunicate CNCs displayed improved mechanical properties compared to either wood or tunicate CNCs, but extruded films did not show this hybrid effect. The water vapor permeability of the extruded nanocomposite films with 1% CNCs was reduced by as much as 60% compared to the PLA films. The composite films also showed enhanced biodegradation compared to neat PLA films. These results demonstrate that wet compounded PLA composites produced with wood or tunicate CNCs modified using a one-pot, water-based route have improved barrier and biodegradation properties, indicating a potential for packaging applications without having to dry the CNCs.

Surfactant Enhanced Bioremediation of Hydrocarbon Contaminated Soils Using Alkyl Polyglucoside

Bioremediation is an efficient and environmentally friendly method for the degradation of petroleum hydrocarbons in contaminated soils. This study investigated the effects of biosurfactant alkyl polyglycosides (APG) on enhanced biodegradation of petroleum hydrocarbon contaminated soils. Three soil samples were contaminated with two different grades of crude oil (medium and Light). Alkyl polyglucoside was synthesised and subjected to FTIR for comfirmation of the product before it was applied in the remediation of contaminated soil. The alkyl polyglucoside is used as a treatment regime in the remediation of the hydrocarbon contamination in the three soil samples. Results of total petroleum hydrocarbons (TPH) before remediation with bio-surfactant showed that samples contaminated with medium crude for Eneka, Ozuoba and Rukpokwu were 15744.00 mg/kg, 11359.00 mg/kg and 11470.00 mg/kg respectively and after remediation reduced to 4276.00 mg/kg, 4265.00 mg/kg, and 3205.00 mg/kg, showing a reduction percentage of 72.84%, 62.44% and 72.05% respectively. Soil samples contaminated with light crude showed result of TPH of 11339.00 mg/kg, 10662 mg/kg and 10226 mg/kg and after remediation reduced to 2981 mg/kg, 3879 mg/kg, and 4245 mg/kg respectively showing a reduction percentage of 73.71%, 63.62 % and 58.49% respectively. The enhanced efficiency of the bio-surfactant at degrading total petroleum hydrocarbons was achieved as a result of the increased solubility thus improving the bioavailability of the hydrocarbons due to the action of the alkyl polyglucoside.