Phenol Degradation by Pseudarthrobacter phenanthrenivorans Sphe3

Batch-mode degradation of high-strength phenolic pollutants by Pseudomonas aeruginosa strain STV1713 immobilized on single and hybrid matrices

Controlled environments are pivotal in all bioconversion processes, influencing the efficacy of biocatalysts. In this study, we designed a batch bioreactor system with a packed immobilization column and a decontamination chamber to enhance phenol and 2,4-dichlorophenol degradation using the hyper-tolerant bacterium Pseudomonas aeruginosa STV1713. When free cells were employed to degrade phenol and 2,4-DCP at a concentration of 1000 mg/L, the cells completely removed the pollutants within 28 h and 66 h, respectively. Simultaneous reductions in chemical oxygen demand and biological oxygen demand were observed (phenol: 30.21 mg/L/h and 16.92 mg/L/h, respectively; 2,4-dichlorophenol: 12.85 mg/L/h and 7.21 mg/L/h, respectively). After assessing the degradation capabilities, the bacterium was immobilized on various matrices (sodium alginate, alginate-chitosan-alginate and polyvinyl alcohol-alginate) to enhance pollutant removal. Hybrid immobilized cells exhibited greater tolerance and degradation capabilities than those immobilized in a single matrix. Among them, polyvinyl alcohol-alginate immobilized cells displayed the highest degradation capacities (up to 2000 mg/L for phenol and 2500 mg/L for 2,4-dichlorophenol). Morphological analysis of the immobilized cells revealed enhanced cell preservation in hybrid matrices. Furthermore, the elucidation of the metabolic pathway through the catechol dioxygenase enzyme assay indicated higher activity of the catechol 1,2-dioxygenase enzyme, suggesting that the bacterium employed an ortho-degradation mechanism for pollutant removal. Additionally, enzyme zymography confirmed the presence of catechol 1,2-dioxygenase, with the molecular weight of the enzyme determined as 245 kDa.

Insights into the influence of polystyrene microplastics on the bio-degradation behavior of tetrabromobisphenol A in soil

Soil contamination by emerging pollutants tetrabromobisphenol A (TBBPA) and microplastics has become a global environmental issue in recent years. However, little is known about the effect of microplastics on degradation of TBBPA in soil, especially aged microplastics. In this study, the effect of aged polystyrene (PS) microplastics on the degradation of TBBPA in soil and the mechanisms were investigated. The results suggested that the aged microplastics exhibited a stronger inhibitory effect on the degradation of TBBPA in soil than the pristine microplastics, and the degradation efficiency of TBBPA decreased by 21.57% at the aged microplastic content of 1%. This might be related to the higher TBBPA adsorption capacity of aged microplastics compared to pristine microplastics. Aged microplastics strongly altered TBBPA-contaminated soil properties, reduced oxidoreductase activity and affected microbial community composition. The decrease in soil oxidoreductase activity and relative abundance of functional microorganisms (e.g., Bacillus, Pseudarthrobacter and Sphingomonas) caused by aged microplastics interfered with metabolic pathways of TBBPA. This study indicated the importance the risk assessment and soil remediation for TBBPA-contaminated soil with aged microplastics.

Phenol biodegradation using bio-filter tower packed column with immobilized bacterial consortium: a batch test study

The effluents from pulp and paper manufacturing industries contain high concentrations of phenol, which when discharged directly into surface water streams, increases the biological oxygen demand (BOD) and chemical oxygen demand (COD). In this study, two dominant bacteria SP-4 and SP-8 were isolated from the effluent emanating with a pulp and paper industry. The selected phenol-degrading isolates were identified as Staphylococcus sp. and Staphylococcus sciuri respectively by using nucleotide sequence alignment and phylogenetic analysis of 16 S rRNA regions of the genome. The two isolates used for the biodegradation process effectively degraded phenol concentration of pulp and paper industry effluent upto 1600 and 1800 mg/L resepctively. The individual isolates and consortium were immobilized using activated carbon, wood dust, and coal ash. Additionally, the effluent was treated using a bio-filter tower packed column immobilized with bacterial cells at a constant flow rate of 5 mL/min. The present study showed that the developed immobilized microbial consortium can effectively degrade 99% of the phenol present in pulp and paper industry effluents, resulting in a significant reduction in BOD and COD of the system. This study can be well implemented on real-scale systems as the bio-filter towers packed with immobilized bacterial consortium can effectively treat phenol concentrations up to 1800 mg/L. The study can be implemented for bioremediation processes in phenolic wastewater-contaminated sites.

Elucidation of 4-Hydroxybenzoic Acid Catabolic Pathways in Pseudarthrobacter phenanthrenivorans Sphe3

4-hydroxybenzoic acid (4-HBA) is an aromatic compound with high chemical stability, being extensively used in food, pharmaceutical and cosmetic industries and therefore widely distributed in various environments. Bioremediation constitutes the most sustainable approach for the removal of 4-hydroxybenzoate and its derivatives (parabens) from polluted environments. Pseudarthrobacter phenanthrenivorans Sphe3, a strain capable of degrading several aromatic compounds, is able to grow on 4-HBA as the sole carbon and energy source. Here, an attempt is made to clarify the catabolic pathways that are involved in the biodegradation of 4-hydroxybenzoate by Sphe3, applying a metabolomic and transcriptomic analysis of cells grown on 4-HBA. It seems that in Sphe3, 4-hydroxybenzoate is hydroxylated to form protocatechuate, which subsequently is either cleaved in ortho- and/or meta-positions or decarboxylated to form catechol. Protocatechuate and catechol are funneled into the TCA cycle following either the β-ketoadipate or protocatechuate meta-cleavage branches. Our results also suggest the involvement of the oxidative decarboxylation of the protocatechuate peripheral pathway to form hydroxyquinol. As a conclusion, P. phenanthrenivorans Sphe3 seems to be a rather versatile strain considering the 4-hydroxybenzoate biodegradation, as it has the advantage to carry it out effectively following different catabolic pathways concurrently.

Revealing the degradation mechanisms of the hyper-tolerant bacterium Pseudomonas aeruginosa STV1713 under high phenol and 2,4-DCP-induced stress conditions through RNA-seq analysis

The ability of bacteria to efficiently remove phenolic pollutants depends on their genetic makeup and environmental conditions. This study examined a novel strain, Pseudomonas aeruginosa STV1713, for degrading higher concentrations of phenol and 2,4-dichlorophenol. After optimization, a combination of degradation parameters, such as pH (7.0), temperature (32.5 °C), and ammonium nitrate concentration (0.7 g/L), was found to reduce degradation time while promoting cell growth. Under these optimal conditions, the bacterium effectively degraded up to 2000 mg/L of phenol and 1400 mg/L of 2,4-dichlorophenol, while maximum tolerance was observed till 2100 mg/L and 1500 mg/L, respectively. Metabolic profiling identified crucial metabolites in the ortho-degradation pathway during pollutant removal. Additionally, transcriptome analysis revealed that P. aeruginosa STV1713 utilizes different branches of the beta ketoadipate pathway for phenol and 2,4-DCP removal. Moreover, under high pollutant stress, the bacterium survived through differential gene expression in ribosome biogenesis, chemotaxis, membrane transport, and other pathways.

Isolation and characterization of the aspartame-degrading strain Pseudarthrobacter sp. AS-1

Aspartame is one of the main varieties of artificial sweeteners. Although it has been approved as a food additive, the environmental hazards and ecological risks posed by aspartame are attracting more and more attention. In the present study, strain Pseudarthrobacter sp. AS-1 was isolated and characterized as an efficient aspartame degrader. Strain AS-1 was capable of degrading 200 mg L-1 aspartame within 10 h under conditions optimized at 30 °C and pH 8.0. At the same time, it was found that enzymes degrading aspartame in strain AS-1 were induced and secreted extracellularly. Degradation of aspartame in Pseudarthrobacter sp. AS-1 was identified as following: it was first demethylated to aspartyl-phenylalanine, then degraded to phenylalanine and aspartate, and finally the two amino acids were further degraded. In addition, strain AS-1 was able to remove more than 85% of aspartame in soil and river water. It is the first time that pure bacterial cultures were reported to have the capability of aspartame degradation. These findings add to our knowledge of the microbial metabolic mechanisms of aspartame.

Evaluation of Bacillus aryabhattai B8W22 peroxidase for phenol removal in waste water effluents

Environmental contamination by phenol has been reported in both aquatic and atmospheric environments. This study aimed to separate and purify the peroxidase enzyme from bacteria that degrade phenol from wastewater sources. An enrichment culture of MSM was used to screen 25 bacterial isolates from different water samples for peroxidase production, six of the isolates exhibited high levels of peroxidase enzyme activity. Qualitative analysis of peroxidase revealed that isolate No. 4 had the highest halo zones (Poly-R478: 14.79 ± 0.78 mm, Azure B: 8.81 ± 0.61 mm). The promising isolate was identified as Bacillus aryabhattai B8W22 by 16S rRNA gene sequencing with accession number OP458197. As carbon and nitrogen sources, mannitol and sodium nitrate were utilized to achieve maximum peroxidase production. A 30-h incubation period was used with pH 6.0, 30 °C, mannitol, and sodium nitrate, respectively, for maximal production of peroxidase. Purified peroxidase enzyme showed 0.012 U/mg specific activity, and SDS-PAGE analysis indicated a molecular weight of 66 kDa. The purified enzyme exhibits maximum activity and thermal stability at pH values of 4.0 and 8.0, respectively, with maximum activity at 30 °C and complete thermal stability at 40 °C. In the purified enzyme, the Km value was 6.942 mg/ml and the Vmax value was 4.132 mol/ml/hr, respectively. The results demonstrated that Bacillus aryabhattai B8W22 has promising potential for degrading phenols from various phenol-polluted wastewater sources.