Iron carriers promote biofilm formation and p-nitrophenol degradation

Impact of arsenic and PAHs compound contamination on microorganisms in coking sites: From a community to individual perspective

Arsenic (As) and polycyclic aromatic hydrocarbons (PAHs) are highly toxic, carcinogenic and teratogenic, and are commonly found in soils of industrial sites such as coking plants. They exert environmental stresses on soil microorganisms, but their compounding effects have not been systematically studied. Exploring the effects of compound contamination on microbial communities, species and genes is important for revealing the ecological damage caused by compound contamination and offering scientific insights into soil remediation strategies. In this study, we selected soil samples from 0 to 100 cm depth of a coking site with As, PAHs and compound contamination. We investigated the compound effects of As and PAHs on microbial communities by combining high-throughput sequencing, metagenomic sequencing and genome assembly. Compared with single contamination, compound contamination reduced the microbial community diversity by 10.68%-12.07% and reduced the community richness by 8.39%-18.61%. The compound contamination decreased 32.41%-46.02% of microbial PAHs metabolic gene abundance, 11.36%-19.25% of cell membrane transport gene abundance and 12.62%-57.77% of cell motility gene abundance. Xanthobacteraceae, the biomarker for compound contaminated soils, harbors arsenic reduction genes and PAHs degradation pathways of naphthalene, benzo [a]pyrene, fluorene, anthracene, and phenanthrene. Its broad metabolic capabilities, encompassing sulfur metabolism and quorum sensing, facilitate the acquisition of energy and nutrients, thereby conferring ecological niche advantages in compound contaminated environments. This study underscores the significant impacts of As and PAHs on the composition and function of microbial communities, thereby enriching our understanding of their combined effects and providing insights for the remediation of compound contaminated sites.

Sequentially modified carbon felt for enhanced p-nitrophenol biodegradation through direct interspecific electron transfer

The widely applied aromatic nitration in modern industry leads to toxic p-nitrophenol (PNP) in environment. Exploring its efficient degradation routes is of great interests. In this study, a novel four-step sequential modification procedure was developed to increase the specific surface area, functional group, hydrophilicity, and conductivity of carbon felt (CF). The implementation of the modified CF promoted reductive PNP biodegradation, attaining 95.2 ± 0.8% of removal efficiency with less accumulation of highly toxic organic intermediates (e.g., p-aminophenol), compared to carrier-free and CF-packed biosystems. The constructed anaerobic-aerobic process with modified CF in 219-d continuous operation achieved further removal of carbon and nitrogen containing intermediates and partial mineralization of PNP. The modified CF promoted the secretion of extracellular polymeric substances (EPS) and cytochrome c (Cyt c), which were essential components to facilitate direct interspecies electron transfer (DIET). Synergistic relationship was deduced that glucose was converted into volatile fatty acids by fermenters (e.g., Longilinea and Syntrophobacter), which donated electrons to the PNP degraders (e.g., Bacteroidetes_vadinHA17) through DIET channels (CF, Cyt c, EPS) to complete PNP removal. This study proposes a novel strategy using engineered conductive material to enhance the DIET process for efficient and sustainable PNP bioremediation.

Recent advances in biological removal of nitroaromatics from wastewater

Various nitroaromatic compounds (NACs) released into the environment cause potential threats to humans and animals. Biological treatment is valued for cost-effectiveness, environmental friendliness, and availability when treating wastewater containing NACs. Considering the significance and wide use of NACs, this review focuses on recent advances in biological treatment systems for NACs removal from wastewater. Meanwhile, factors affecting biodegradation and methods to enhance removal efficiency of NACs are discussed. The selection of biological treatment system needs to consider NACs loading and cost, and its performance is affected by configuration and operation strategy. Generally, sequential anaerobic-aerobic biological treatment systems perform better in mineralizing NACs and removing co-pollutants. Future research on mechanism exploration of NACs biotransformation and performance optimization will facilitate the large-scale application of biological treatment systems.