Halophilic Martelella sp. AD-3 enhanced phenanthrene degradation in a bioaugmented activated sludge system through syntrophic interaction

Hydrogel immobilized bacteria@metal-organic-frameworks composite augmented bisphenol A removal from activated sludge and its regulation behavior on sludge community

Improving degradation efficiency of activated sludge towards bisphenol A (BPA) is related to water safety. A hydrogel immobilized bacteria@metal-organic-frameworks (im-SQ-2@MOFs) was synthesized previously, which was a composite formed by metal organic frameworks adhering to BPA degrading bacteria. Accordingly, this study added im-SQ-2@MOFs as enhancer to augment the BPA degradation ability of activated sludge. Results indicated that after the addition of im-SQ-2@MOFs, the augmented activated sludge system maintained 90 % BPA degradation rate for 10 mg/L BPA. Meanwhile, the system also presented 80-97 % degradation effect for other phenolic pollutants. Augmentation mechanism was revealed through multi-omics analysis. Firstly, im-SQ-2@MOFs enriched the degradation functional microorganisms in activated sludge, and microbial communication was further prompted. Besides, organic compounds degrading enzymes were upregulated to intensify BPA hydrolysis. Furthermore, electron transfer during BPA degradation was accelerated. Results provide new perspective on the development of bio-augmented materials to improve the efficiency of sewage treatment plants. TAKE HOME MESSAGE.

Degradation of Polyaromatic Hydrocarbons by Biosurfactant-Producing Pseudomonas aeruginosa NG4

Polyaromatic hydrocarbons (PAHs) are a group of organic pollutants commonly found in the environment due to industrial activities, incomplete burning of fossil fuels, and oil spills. Bioremediation of PAHs has emerged as a promising approach. This study investigated the biodegradation of PAHs (anthracene, naphthalene, phenanthrene, anthraquinone, and anthrone) at 100 ppm to 1000 ppm in the presence of glucose and glycerol by a biosurfactant-producing strain of Pseudomonas aeruginosa NG4. The quality of the biosurfactant produced by the bacterial strain was analyzed via emulsion index (E24), drop-collapse assay, and oil displacement assay. The PAH degradation efficiency was studied by HPLC and degradation metabolites were analyzed using GC-MS. Among all five PAHs (fed at 300 ppm), the highest degradation rates of 91.16 ± 3.64% naphthalene and 41.16 ± 1.64% anthrone were observed by P. aeruginosa NG4 after 10 days of incubation. The assessment of degradation intermediate metabolites revealed the PAH catabolism via the dioxygenase route, which plays a key role in the breakdown of these aromatic compounds. Biodegradation of anthrone by P. aeruginosa NG4 at a 300 ppm level in the media was reported for the first time. This study highlights the potential of P. aeruginosa NG4 as a candidate for the development of bioremediation strategies to mitigate environmental pollution caused by persistent organic pollutants like PAHs.

Optimizing carbon sources regulation in the biochemical treatment systems for coal chemical wastewater: Aromatic compounds biodegradation and microbial response strategies

The complex composition of coal chemical wastewater (CCW), marked by numerous highly toxic aromatic compounds, induces the destabilization of the biochemical treatment system, leading to suboptimal treatment efficacy. In this study, a biochemical treatment system was established to efficiently degrade aromatic compounds by quantitatively regulating the dosage of co-metabolized substrates (specifically, the chemical oxygen demand (COD) Glucose: COD Sodium acetate = 3:1, 1:3, and 1:1). The findings demonstrated that the system achieved optimal performance under the condition that the ratio of COD Glucose to COD Sodium acetate was 3:1. When the co-metabolized substrate was added to the system at an optimal ratio, examination of pollutant removal and cumulative effects revealed that the removal efficiencies for COD and total organic carbon (TOC) reached 94.61 % and 86.40 %, respectively. The removal rates of benzene series, nitrogen heterocyclic compounds, polycyclic aromatic hydrocarbons, and phenols were 100 %, 100 %, 63.58 %, and 94.12 %, respectively. Research on the physiological response of microbial cells showed that, under optimal ratio regulation, co-metabolic substrates led to a substantial rise in microbial extracellular polymeric substances (EPS) secretion, particularly extracellular proteins. When the system reached the end of its operation, the contents of loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) for proteins in the optimal group were 7.12 mg/g-SS and 152.28 mg/g-SS, respectively. Meanwhile, the ratio of α-Helix / (β-Sheet + Random coil) and the proportion of intermolecular interaction forces were also increased in the optimal group. At system completion, the ratio of α-Helix / (β-Sheet + Random coil) reached 0.717 (LB-EPS) and 0.618 (TB-EPS), respectively. Additionally, the proportion of intermolecular interaction forces reached 74.83 % (LB-EPS) and 55.03 % (TB-EPS). An in-depth analysis of the metabolic regulation of microorganisms indicated that the introduction of optimal ratios of co-metabolic substrates contributed to a noteworthy upregulation in the expression of Catechol 2,3-dioxygenase (C23O) and Dehydrogenase (DHA). The expression levels of C23O and DHA were measured at 0.029 U/mg Pro·g MLSS and 75.25 mg TF·(g MLSS·h)-1 (peak value), respectively. Correspondingly, enrichment of aromatic compound-degrading bacteria, including Thauera, Saccharimonadales, and Candidatus_Competibacter, occurred, along with the upregulation of associated functional genes such as Catechol 1,2-dioxygenase, Catechol 2,3-dioxygenase, Protocatechuate 3,4-dioxygenase, and Protocatechuate 4,5-dioxygenase. Considering the intricate system of multiple coexisting aromatic compounds in real CCW, this study not only obtained an optimal ratio for carbon source addition but also enhanced the efficient utilization of carbon sources and improved the capability of the system to effectively degrade aromatic compounds. Additionally, this paper established a theoretical foundation for metabolic regulation and harmless treatment within the biochemical treatment of intricate systems, exemplified by real CCW.

A novel remediation strategy of mixed calcium peroxide and degrading bacteria for polycyclic aromatic hydrocarbon contaminated water

Polycyclic aromatic hydrocarbons (PAHs) are a class of toxic organic pollutants commonly detected in the aqueous phase. Traditional biodegradation is inefficient and advanced oxidation technologies are expensive. In the current study, a novel strategy was developed using calcium peroxide (CP) and PAH-degrading bacteria (PDB) to effectively augment PAH degradation by 28.62-59.22%. The PDB consisted of the genera Acinetobacter, Stenotrophomonas, and Comamonas. Applying the response surface model (RSM), the most appropriate parameters were identified, and the predictive degradation rates of phenanthrene (Phe), pyrene (Pyr), and ΣPAHs were 98%, 76%, and 84%, respectively. The constructed mixed system could reduce 90% of Phe and more than 60% of ΣPAHs and will perform better at pH 5-7 and lower salinity. Because PAHs tend to bind to dissolved organic matter (DOM) with larger molecular weights, humic acid (HA) had a larger negative effect on the PAH-degradation efficiency of the CP-PDB mixed system than fulvic acid (FA). The proposed PAH-degradation pathways in the mixed system were based on the detection of intermediates at different times. The investigation constructed and optimized a novel environmental PAH-degradation strategy. The synergistic application of PDB and oxidation was extended for organic contaminant degradation in aqueous environments.

Biosurfactants-based mixed polycyclic aromatic hydrocarbon degradation: From microbial community structure toward non-targeted metabolomic profile determination

Biosurfactants-based bioremediation is considered an efficient technology to eliminate environmental pollutants including polycyclic aromatic hydrocarbons (PAHs). However, the precise role of rhamnolipids or lipopeptide-biosurfactants in mixed PAH dissipation, shaping microbial community structure, and influencing metabolomic profile remained unclear. In this study, results showed that the maximum PAH degradation was achieved in lipopeptide-assisted treatment (SPS), where the pyrene and phenanthrene were substantially degraded up to 74.28 % and 63.05 % respectively, as compared to rhamnolipids (SPR) and un-aided biosurfactants (SP). Furthermore, the high throughput sequencing analysis revealed a significant change in the PAH-degrading microbial community, with Proteobacteria being the predominant phylum (>98 %) followed by Bacteroidota and Firmicutes in all the treatments. Moreover, Pseudomonas and Pannonibacter were found as highly potent bacterial genera for mixed PAH degradation in SPR, SPS, and SP treatments, nevertheless, the abundance of the genus Pseudomonas was significantly enhanced (>97 %) in SPR treatment groups. On the other hand, the non-targeted metabolomic profile through UHPLC-MS/MS exhibited a remarkable change in the metabolites of amino acids, carbohydrates, and lipid metabolisms by the input of rhamnolipids or lipopeptide-biosurfactants whereas, the maximum intensities of metabolites (more than two-fold) were observed in SPR treatment. The findings of this study suggested that the aforementioned biosurfactants can play an indispensable role in mixed PAH degradation as well as seek to offer new insights into shifts in PAH-degrading microbial communities and their metabolic function, which can guide the development of more efficient and targeted strategies for complete removal of organic pollutants such as PAH from the contaminated environment.

Mitigating the inhibition of antibacterial agent chloroxylenol on nitrification system-The role of Rhodococcus ruber in a bioaugmentation system

The chloroxylenol (PCMX) degrading strain was successfully isolated from sludge and identified as Rhodococcus ruber (R. ruber). Afterwards, a bioaugmentation system was constructed by seeding R. ruber into nitrifying sludge to fasten degradation efficiency of highly toxic PCMX from wastewater. Results showed that R. ruber presented high PCMX-degrading performance under aerobic conditions, 25 °C, pH 7.0 and inoculum sizes of 4% (v/v). These optimized conditions were used in subsequent bioaugmentation experiment. In bioaugmentation system, R. ruber could detoxify nitrifiers by degrading PCMX, and the content of polysaccharide in extracellular polymeric substances increased. The quantitative polymerase chain reaction results exhibited that the absolute abundance of 16S rRNA gene and ammonia oxidizing bacteria (AOB) slightly elevated in bioaugmentation system. After analyzing the results of high-throughput sequencing, it was found that the loaded R. ruber can colonize successfully and turn into dominant strains in sludge system. Molecular docking simulation showed that PCMX had a weaker suppressed effect on AOB than nitrite oxidizing bacteria, and R. ruber can alleviate the adverse effect. This study could provide a novel strategy for potential application in reinforcement of PCMX removal in wastewater treatment.

Efficient biodegradation of acetoacetanilide in hypersaline wastewater with a synthetic halotolerant bacterial consortium

The high concentrations of salt and refractory toxic organics in industrial wastewater seriously restrict biological treatment efficiency and functional stability. However, how to construct a salt-tolerant biocatalytic community and realize the decarbonization coupled with detoxification toward green bio-enhanced treatment, has yet to be well elucidated. Here, acetoacetanilide (AAA), an important intermediate for many dyes and medicine synthesis, was used as the model amide pollutant to elucidate the directional enrichment of halotolerant degradative communities and the corresponding bacterial interaction mechanism. Combining microbial community composition and molecular ecological network analyses as well as the biodegradation efficiencies of AAA and its hydrolysis product aniline (AN) of pure strains, the core degradative bacteria were identified during the hypersaline AAA degradation process. A synthetic bacterial consortium composed of Paenarthrobacter, Rhizobium, Rhodococcus, Delftia and Nitratireductor was constructed based on the top-down strategy to treat AAA wastewater with different water quality characteristics. The synthetic halotolerant consortium showed promising treatment ability toward the simulated AAA wastewater (AAA 100-500 mg/L, 1-5% salinity) and actual AAA mother liquor. Additionally, the comprehensive toxicity of AAA mother liquor significantly reduced after biological treatment. This study provides a green biological approach for the treatment of hypersaline and high concentration of organics wastewater.