Nonlinear responses of biofilm bacteria to alkyl-chain length of parabens by DFT calculation.

Parabens can particularly raise significant concerns regarding the disruption of microbial ecology due to their antimicrobial properties. However, the responses of biofilm bacteria to diverse parabens with different alkyl-chain length remains unclear. Here, theoretical calculations and bioinformatic analysis were performed to decipher the influence of parabens varying alkyl-chain lengths on the biofilm bacteria. Our results showed that the disturbances in bacterial community did not linearly response to the alkyl-chain length of parabens, and propylparaben (PrP), with median chain length, had more severe impact on bacterial community. Despite the fact that paraben lethality linearly increased with chain length, the PrP had a higher chemical reactions potential than parabens with shorter or longer alkyl-chain. The chemical reactions potential was critical in the nonlinear responses of bacterial community to alkyl-chain length of parabens. PrP could impose selective pressure to disturb the bacterial community, because it had a more profound contribution to deterministic assembly process. Furthermore, N-acyl-homoserine lactones was also significantly promoted under PrP exposure, confirming that PrP could affect the bacterial community by influencing the quorum-sensing system. Overall, our study reveals the nonlinear responses of bacterial communities to the alkyl-chain lengths of parabens and provides insightful perspectives for the better regulation of parabens. ENVIRONMENTAL IMPLICATION: Parabens are recognized as emerging organic pollutants, which specially raise great concerns due to their antimicrobial properties disturbing microbial ecology. However, few study have addressed the relationship between bacterial community responses and the molecular structural features of parabens with different alkyl-chain length. This investigation revealed nonlinear responses of the bacterial community to the alkyl-chain length of parabens through DFT calculation and bioinformatic analysis and identified the critical roles of chemical reactions potential in nonlinear responses of bacterial community. Our results benefit the precise evaluation of ecological hazards posed by parabens and provide useful insights for better regulation of parabens.

Revealing bioresponses of biofilm and flocs to salinity gradient in halophilic biofilm reactor.

Understanding the different biological responses to salinity gradient between coexisting biofilm and flocs is crucial for regulating the ecological function of biofilm system. This study investigated performance, dynamics, and community assembly of biofilm system under 3 %-7% salinity gradient. The removal efficiency of NH4+-N remained stable and exceeded 93 % at 3 %-6% salinity, but decreased to below 80 % at 7 % salinity. The elevated salinity promoted the synthesis of extracellular polymer substrates, inhibited microbial respiration, and significantly regulated the microbial community structure. Compared to flocs, biofilm exhibited greater species diversity and richer Nitrosomonas. It was found diffusion limitations dominated the microbial community assembly under the salinity gradient. And microbial network revealed positive interactions predominated the microbial relationships, designating norank Spirochaetaceae, unclassified Micrococcales, Corynebacterium, and Pusillimonas as keystone species. Moreover, distinct salinity preferences in nitrogen transformation-related genes were observed. This study can improve the understanding to the regulation of biofilm systems to salt stresses.

Recovery mechanism of heterotrophic ammonia assimilation system under chromium hexavalent stress.

Heterotrophic ammonia assimilation (HAA), an innovative technology for high-salinity wastewater treatment, demonstrates self-recovery capability following Cr (VI) stress. This study investigated the inhibitory effects and self-restoration mechanisms of Cr (VI) at various stress levels. The removal efficiencies of NH4+-N and Cr (VI) in the HAA gradually decreased with increasing influent Cr (VI) concentration. Exposure to Cr (VI) increased the amounts of high-molecular-weight proteins in soluble microbial products and stimulated the generation of extracellular polymeric substances. Heterotrophic functional microorganisms with Cr (VI) tolerance, such as Marinobacter and Planktosalinus, were enriched. An assimilation pathway gene (glnA) and a Cr (VI)-related gene (atoB) were also upregulated. After ceasing Cr (VI) addition, the HAA system demonstrated a 17.1 % increase in the removal efficiency of NH4+-N, which was attributable to its self-recovery ability. This study provides a scientific and theoretical foundation for the HAA process in resisting the impact of heavy-metal-containing wastewater and self-recovery.

Nutrients recovery by coupled bioreactor of heterotrophic ammonia assimilation and microbial fuel cell in saline wastewater.

Heterotrophic ammonia assimilation (HAA) process had been widely used in the treatment of high salt wastewater, but the electro enhanced coupling process and electron transfer process were rarely studied. In this study, a HAA process coupled microbial fuel cell (MFC) system was established to treat ammonia-containing wastewater under increasing salinity to achieve nitrogen recovery and electricity generation. Up to 95.4 % NH4+-N and 96.4 % COD removal efficiencies were achieved at 2 % salinity in HAA-MFC. The maximum power density and current density at 2 % salinity were 29.93 mW/m2 and 182.37 mA/m2, respectively. The residual organic matter in the cathode effluent was effectively removed by the anode. The increase of salinity not only enhanced the sludge settling performance and activity, but also promoted the enzyme activity and amino acid production of the ammonia assimilation pathway. Marinobacter and Halomonas were gradually enriched at the anode and cathode with increased salinity to promote ammonia assimilation and electron production. This research offered a promising solution to overcome salinity-related challenges in wastewater treatment and resource recovery.

Novel strategy for treating high salinity oilfield produced water: Pyrite-activated peroxymonosulfate coupled with heterotrophic ammonia assimilation.

Existing conventional biological treatment techniques face numerous limitations in effectively removing total petroleum hydrocarbons (TPHs) and ammonia (NH4+-N) from oilfield-produced water (OPW), highlighting the pressing need for innovative pre-oxidation and biological treatment processes. In this study, a pyrite-activated peroxymonosulfate (PMS)-coupled heterotrophic ammonia assimilation (HAA) system was established to achieve satisfactory system performance for OPW treatment. Pyrite sustained-release Fe2+-activated PMS was used to produce SO4•- and •OH, and 71.0 % of TPHs were effectively removed from the oil wastewater. The average TPHs and NH4+-N removal efficiencies in the test group with pre-oxidation were 96.9 and 98.3 %, compared to 46.5 and 77.1 % in the control group, respectively. The maximum fluorescence intensities of tryptophan protein and aromatic protein in the test group declined by 83.7 %. Fourier transform ion cyclotron resonance mass spectrometry revealed that pre-oxidation degraded more long-chain hydrocarbons and aromatic family compound, whereas the HAA process produced more proteins and carbohydrates. Pyrite-PMS promoted the enrichment of ammonia-assimilating bacteria, alleviating the explosive increase in extracellular polymeric substances and reducing sludge settleability. The low cost, efficiency, green chemistry principles, and synergies of this approach make it a powerful solution for practical OPW treatment to reduce environmental impacts and promote sustainable wastewater treatment.

Enhanced degradation of petroleum in saline soil by nitrogen stimulation and halophilic emulsifying bacteria Bacillus sp. Z-13.

Remediation of petroleum-contaminated soil is a widely concerned challenge. As an ecofriendly method, the performance improvement of indigenous microbial degradation is facing the bottleneck. In this study, a strain with high efficiency of petroleum degradation was isolated from the petroleum-contaminated soil and identified and named as Bacillus sp. Z-13. The strain showed the ability to produce lipopeptide surfactant which could improve 66% more petroleum hydrocarbons eluted. Strain Z-13 and its biosurfactant exhibited broad environmental adaptability to salinity (0-8%), pH (6-9) and temperature (15-45 °C). With the addition of strain Z-13 and the stimulation of NH4Cl, up to 59% of the petroleum in the contaminated soil was removed at the carbon to nitrogen ratio of 10. Microbial community analysis showed that petroleum-degrading bacteria, represented by Bacillus, became the dominant species at genus level and played an important role in the remediation. Additionally, ammonium stimulation facilitated both pathways of ammonium assimilation and nitrification in native microorganisms to achieve efficient degradation of petroleum hydrocarbons. This study could provide a promising approach for stable, environmental-friendly and efficient remediation of petroleum-contaminated soil.

Responses of halophilic microbial communities to changes in salt composition: Comparison between autotrophic nitrification and heterotrophic ammonia assimilation biosystems.

The concentration and proportion of chlorine (Cl-) and sulfate ions (SO42-) in actual high salinity wastewater exhibit significant fluctuations due to their diverse sources. This study compared the response of halophilic autotrophic nitrification (AN) and heterotrophic ammonia assimilation (HAA) sludges to changes in salt composition. The results demonstrated that both the AN and HAA systems maintained high ammonia removal efficiency even when exposed to mixed salt ions or pure sulfate conditions. Increasing the concentration of SO42- resulted in an increase in extracellular polymeric substances content, sludge settleability, sludge hydrophobicity, and the relative abundance of Nitrosomonas in the AN system (from 2.3% to 10.4%). The dominant heterotrophic bacteria in the HAA system underwent turnover in response to changes in salt composition conditions. The robustness and the cooperation between microorganisms of the HAA system surpassed those of the AN system. This study provides scientific foundation for treating multi-ion high salinity wastewater.

Solid slow-release carbon source assembled microbial fuel cell for promoting superior nitrogen removal in an aerobic granular sludge bioreactor.

Although the coupling process of microbial fuel cell (MFC) and activated sludge is widely used for organic matter removal and electric energy recovery, the problem of high effluent nitrate still exists due to the lack of influent carbon source. Herein, a poly (butanediol succinate) (PBS) assembled MFC was established in an aerobic granular sludge (AGS) bioreactor for simultaneous promoting nitrogen removal and electricity generation. Compared to AGS-Control group, the total inorganic nitrogen (TIN) and COD removal efficiencies of AGS-MFC group were improved to 84.3 ± 2.6% and 93.5 ± 0.5% after 100-days operation. The average output voltage and the maximum power density of the MFC module were 223.7 mV and 59.6 mW/m2, respectively. Through high-throughput sequencing analysis, Thauera-related denitrifying bacteria had the highest relative abundances (20.0% and 31.4%) in both bioreactors. The relative abundance of Nitrosomonas-related ammonia oxidizing bacteria (AOB) in AGS-MFC (1.8%) was enriched than AGS-Control (1.1%). In MFC module, Thauera (16.2%) with denitrification and power generation was dominant in anodic biofilms under PBS enhancement. This study provides scientific basis for the application of submersible MFC enhanced deep nitrogen removal under aerobic conditions.

Microbial fuel cell enhanced pollutants removal in a solid-phase biological denitrification reactor: System performance, bioelectricity generation and microbial community analysis.

A novel electrochemical system of microbial fuel cell (MFC) coupled solid-phase denitrification biofilm reactor (DBR) system was established to explore the effect of simultaneous power generation and pollutant removal under different HRTs (Ⅰ:48 h; Ⅱ :24 h). The average removal rates of methyl orange, Cr (VI) and NO3--N in test group were 93.0, 98.6 and 95.5% within 60 days, while those were 53.1, 72.1 and 72.7% in control. The maximum power density was 61.2 (Ⅰ) and 16.1 mW/m2 (Ⅱ), while average output voltage was 122 (Ⅰ) and 83.6 mV (Ⅱ). Components 1 and 2 in soluble microbial products were identified, and the humic-like and fulvic acid-like substances varied through different layers. Pseudomonas produced electricity in anode, while denitrified in denitrification layer. Importantly, symbiotic cooperation was absolutely dominant in network analysis of both anodic and denitrifying biofilms. MFC significantly improved DBR's ability to treatment co-polluted wastewater.

Coupling of nitrifying granular sludge into microbial fuel cell system for wastewater treatment: System performance, electricity production and microbial community shift.

A novel electrochemical system coupling of nitrifying granular sludge (NGS) into microbial fuel cell (MFC) system was conducted for simultaneous electricity production and wastewater treatment under sequencing batch mode. After 60 days operation, the contaminants of organic and NH4+-N removal efficiencies of the system were high of 95.43% and 98.55%, respectively. The maximum output voltage and power density of the MFC were average at 170 mV and 33.24 mW/m2, respectively. According to EEM-PARAFAC model, the soluble microbial products (SMP) released from anode and cathode chambers could be identified two fluorescence components. Additionally, the fluorescence score of protein-like substances changed more obvious than those of humic-like and fulvic acid-like substances. Geobacter and Nitrospiraceae were the dominant functional populations in the anode and cathode chambers, respectively. The result could provide a potential application technology based on NGS-MFC for simultaneously treatment of organic matter and ammonia.