The changing C/N of aggressive aniline: Metagenomic analysis of pollutant removal, metabolic pathways and functional genes

Harnessing diurnal dynamics: Understanding the influence of light-dark cycle on algal-bacterial symbiotic system under aniline stress

To assess the inherent effects of light-dark cycle on the aniline degradation and nitrogen removal in algal-bacterial symbiotic system, three groups with different photoperiods (0L:12D;6L:6D;12L:0D) were set up. The results revealed that the aniline degradation rate of the three systems all surpassed 99 %, the total nitrogen removal rate of Z2-6L:6D was approximately 36 % higher than Z1-0L:12D eventually, the Z1-0L:12D was restrained by NH4+-N assimilation and nitrification while anoxic denitrification in Z3-12L:0D. The disappearance of microalgae biomass was accompanied by the sharp decreased of polysaccharide in Z1 and longer illumination suppressed the secretion of extracellular polymeric substances, the Z3 yielded slightly superior biomass production despite the double illumination compared with Z2. Moreover, high throughput sequencing analysis illustrated that the microbial community structure in Z2 was more abundant and even than Z3, the TM7a, norank_f__norank_o__Saccharimonadales, Ellin6067 and Scenedesmus proliferated wildly and the photoinhibition to functional genus was effectively alleviated in Z2.

Unraveling the mechanisms and responses of aniline-degrading biosystem to salinity stress in high temperature condition: Pollutants removal performance and microbial community

To explore the intrinsic influence of different salinity content on aniline biodegradation system in high temperature condition of 35 ± 1 °C, six groups at various salinity concentration (0.0%-5.0%) were applied. The results showed that the salinity exerted insignificant impact on aniline removal performance. The low-level salinity (0.5%-1.5%) stimulated the nitrogen metabolism performance. The G5-2.5% had excellent adaptability to salinity while the nitrogen removal capacity of G6-5.0% was almost lost. Moreover, high throughput sequencing analysis revealed that the g__norank_f__NS9_marine_group, g__Thauera and g__unclassified_f__Rhodobacteraceae proliferated wildly and established positive correlation each other in low salinity systems. The g__SM1A02 occupying the dominant position in G5 ensured the nitrification performance. In contrast, the Rhodococcus possessing great survival advantage in tremendous osmotic pressure competed with most functional genus, triggering the collapse of nitrogen metabolism capacity in G6. This work provided valuable guidance for the aniline wastewater treatment under salinity stress in high temperature condition.

Metagenomics and metatranscriptomics suggest pathways of 3-chloroaniline degradation in wastewater reactors

Biological wastewater treatment systems are often affected by shifts in influent quality, including the input of toxic chemicals. Yet the mechanisms underlying the adaptation of activated sludge process performance are rarely studied in a controlled and replicated experimental setting, particularly when challenged with a sustained toxin input. Three replicate bench-scale bioreactors were subjected to a chemical disturbance in the form of 3-chloroaniline (3-CA) over 132 days, after an acclimation period of 58 days, while three control reactors received no 3-CA input. Ammonia oxidation was initially affected by 3-CA. Within three weeks of the experiment, microbial communities in all three treatment reactors adapted to biologically degrade 3-CA resulting in partial ammonia oxidation recovery. Combining process and microbial community data from amplicon sequencing with potential functions gleaned from assembled metagenomics and metatranscriptomics data, two putative degradation pathways for 3-CA were identified. The first pathway, determined from metagenomics data, involves a benzoate dioxygenase and subsequent meta-cleavage of the aromatic ring. The second, determined from intensive short-term sampling for gene expression data in tandem with 3-CA degradation, involves a phenol monooxygenase followed by ortho-cleavage of the aromatic ring. The relative abundances of amplicon sequence variants associated with the genera Gemmatimonas, OLB8, and Taibaiella correlated significantly with 3-CA degradation. Metagenome-assembled genome data also showed the genus OLB8 to be differentially enriched in treatment reactors, making it a strong candidate as 3-CA degrader. Using replicated reactors, this study has demonstrated the impact of a sustained stress on the activated sludge process. The unique and novel features of this study include the identification of putative pathways and potential degraders of 3-CA using long-term and short-term sampling in tandem with multiple methods in a controlled and replicated experiment.

Elucidating the roles of Cr(VI)-Cu(II) Co-pollution in the stress of aniline degradation stress: Insights into metabolic pathways and functional genes

In order to examine the impact of Cu(II)-Cr(VI) co-pollution in printing and dyeing wastewater on the aniline biodegradation system (ABS), loading experiments were conducted on ABS at varying concentrations of Cu(II)-Cr(VI). The synergistic stress imposed by Cu(II)-Cr(VI) accelerated the deterioration of the systems, with only the C2-3 (2 mg/L Cr(VI)-3 mg/L Cu(II)) sustaining stable operation for 42 days. However, its nitrogen removal performance remained significantly impaired, resulting in a total nitrogen (TN) removal rate below 40%. High-throughput sequencing analysis revealed a stronger correlation between Cr(VI) and microbial diversity compared to Cu(II). Metagenomic sequencing results demonstrated that Cu(II) emerged as the dominant factor influencing the distribution of dominant bacteria in C2-3, as well as its contribution to contaminant degradation. The complex co-pollution systems hindered aniline degradation and nitrogen metabolism through the combined bio-toxicity of heavy metals and aniline, thereby disrupting the transport chain within the systems matrix.

Unraveling the nexus of Cr (Ⅵ), Aniline, and Microbial Ecology on aniline-degrading biosystem: Removal efficiency, sludge type, microbial ecology

In order to explore the stress principle of Cr (Ⅵ) on aniline biodegradation system, a control group and experimental groups with the concentration of Cr (Ⅵ) at 2, 5, 8 mg/L were set up. The results demonstrated that Cr (Ⅵ) had minimal effects on the degradation efficiency of aniline but significantly inhibited nitrogen removal function. When Cr (Ⅵ) concentration was below 5 mg/L, the nitrification performance recovered spontaneously, while denitrification performance was severely impaired. Furthermore, the secretion of extracellular polymeric substances (EPS) and its fluorescence substance concentration were strongly inhibited with increasing Cr (Ⅵ) concentration. High-throughput sequencing revealed that the experimental groups were enriched with Leucobacter and Cr (Ⅵ)-reducing bacteria, but the abundance of nitrifiers and denitrifiers was significantly decreased compared to the control group. Overall, the effects of Cr (Ⅵ) stress at different concentrations on nitrogen removal performance were more significant than those on aniline degradation.

Retrospect and prospect of aerobic biodegradation of aniline: Overcome existing bottlenecks and follow future trends

Aniline is a highly bio-toxic industrial product, even at low concentrations, whose related wastewater has been flowing out worldwide on a large scale along with human production. As a green technology, aerobic biological treatment has been widely applied in industrial wastewater and exhibited various characteristics in the field of aniline wastewater. Meanwhile, this technology has shown its potential of synchronous nitrogen removal, but it still consumes energy badly. In the face of resource scarcity, this review comprehensively discusses the existing research in aerobic biodegradation of aniline wastewater to find out the developmental dawn of aerobic biological treatment. Primarily, it put forward the evolution history details of aniline biodegradation from pure culture to mixed culture and then to simultaneous nitrogen removal. On this basis, it presented the existing challenges to further expand the application of aerobic biotechnology, including the confusions of aniline metabolic mechanism, the development of co-degradation of multiple pollutants and the lack of practical experience of bioreactor operation for aniline and nitrogen removal. Additionally, the prospects of the technological shift to meet the needs of an energy-conserving society was described according to existing experiences and feasibility. Including but not limiting to the development of multifunctional bacteria, the reduction of greenhouse gases and the combination of green technologies.