This review highlights the relevance of bioremediation techniques for the removal of emerging pollutants (EPs). The EPs are chemical or biological pollutants that are not currently monitored or regulated by environmental authorities, but which can enter the environment and cause harmful effects to the environment and human health. In recent times, an ample range of EPs have been found in water bodies, where they can unbalance ecosystems and cause negative effects on non-target species. In addition, some EPs have shown high rates of bioaccumulation in aquatic species, thus affecting the safety and quality of seafood. The negative impacts of emerging pollutants, their wide distribution in the environment, their bioaccumulation rates, and their resistance to wastewater treatment plants processes have led to research on sustainable remediation. Remediation techniques have been recently directed to advanced biological remediation technologies. Such technologies have exhibited numerous advantages like in-situ remediation, low costs, eco-friendliness, high public acceptance, and so on. Thus, the present review has compiled the most recent studies on bioremediation techniques for water decontamination from emerging pollutants to extend the current knowledge on sustainable remediation technologies. Biological emerging contaminants, agrochemicals, endocrine-disrupting chemicals, and pharmaceutical and personal care products were considered for this review study, and their removal by bioremediation techniques involving plants, bacteria, microalgae, and fungi. Finally, further research opportunities are presented based on current challenges from an economic, biological, and operation perspective. 

Bio-removal of emerging pollutants by advanced bioremediation techniques.

In situ restoration of soil ecological function in a coal gangue reclamation area after 10 years of elm/poplar phytoremediation.

While the genus Variovorax is known for its aromatic compound metabolism, no detailed study of the peripheral and central pathways of aromatic compound degradation has yet been reported. Variovorax sp. PAMC26660 is a lichen-associated bacterium isolated from Antarctica. The work presents the genome-based elucidation of peripheral and central catabolic pathways of aromatic compound degradation genes in Variovorax sp. PAMC26660. Additionally, the accessory, core and unique genes were identified among Variovorax species using the pan genome analysis tool. A detailed analysis of the genes related to xenobiotic metabolism revealed the potential roles of Variovorax sp. PAMC26660 and other species in bioremediation.TYGS analysis, dDDH, phylogenetic placement and average nucleotide identity (ANI) analysis identified the strain as Variovorax sp. Cell morphology was assessed using scanning electron microscopy (SEM). On analysis of the core, accessory, and unique genes, xenobiotic metabolism accounted only for the accessory and unique genes. On detailed analysis of the aromatic compound catabolic genes, peripheral pathway related to 4-hydroxybenzoate (4-HB) degradation was found among all species while phenylacetate and tyrosine degradation pathways were present in most of the species including PAMC26660. Likewise, central catabolic pathways, like protocatechuate, gentisate, homogentisate, and phenylacetyl-CoA, were also present. The peripheral pathway for 4-HB degradation was functionally tested using PAMC26660, which resulted in the growth using it as a sole source of carbon.Computational tools for genome and pan genome analysis are important to understand the behavior of an organism. Xenobiotic metabolism-related genes, that only account for the accessory and unique genes infer evolution through events like lateral gene transfer, mutation and gene rearrangement. 4-HB, an aromatic compound present among lichen species is utilized by lichen-associated Variovorax sp. PAMC26660 as the sole source of carbon. The strain holds genes and pathways for its utilization. Overall, this study outlines the importance of Variovorax in bioremediation and presents the genomic information of the species. 

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Comparative genome analysis among Variovorax species and genome guided aromatic compound degradation analysis emphasizing 4-hydroxybenzoate degradation in Variovorax sp. PAMC26660

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Two-liquid-phase(silicone oil-water) culture enrichment systems,with anthracene as carbon source,was used to enrichment PAHs-degrading strains from contaminated soil by crude oil.One strain,which can degrade phenanthrene,anthracene,fluoranthene,pyrene and benzo[a]pyrene,was isolated and identified as Sphingobium yanoikuyae based on 16S rDNA sequences,phenotypic characteristics and physio-biochemistry characteristics,and numbered as LD29.Degradation characteristics of LD29 in mineral salts medium(MSM) was measured by HPLC.After 4 days of growing in MSM with single PAH as carbon source,LD29 degraded phenanthrene,anthracene,fluoranthene,pyrene(initial concentration: 50 mg/L) by 92%,87%,28% and 7% respectively,but no benzo[a]pyrene was degraded.Anthracene enhanced the degradation of fluoranthene/pyrene by LD29,whereas fluoranthene/pyrene impeded anthracene degradation by LD29.MSM with high initial pH value(pH=9) favored the degradation of PAHs mixture in MSM by LD29.The degradation activity of LD29 can be improved by additional nutrition.Additional carbon source(glucose,200 mg/L) or nitrogen source(peptone,50 mg/L) accelerated fluoranthene(100 mg/L) degradation in MSM,with degradation rate 69%,81% respectively(CK: 34%) within 6 days.LD29 started to significantly degrade HMW PAHs from the 4th day in MSM with 5 PAHs(phenanthrene,anthracene,fluoranthene,pyrene and benzo[a]pyrene),and the degradation rate of pyrene and fluoranthene at day 6 were 44% and 58% higher than those of day 4 respectively,and the degradation rate of benzo[a]pyrene also reached to 17% at day 6.LD29 has significant potential for PAHs degradation,including high molecular weight(HMW) PAHs.

Isolation and Degradation Characteristics of a HMW PAHs-Degrading Strain LD29

Polycyclic aromatic hydrocarbons (PAHs) are frequently detected in soil. Their biological toxicity and carcinogenic, teratogenic, and mutagenic effects pose a great threat to the ecological environment and human health. Firstly, the sources, physicochemical properties, and environmental hazards of PAHs are reviewed in this paper, and then their pollution status and different methods for their detection in soil are described in detail. The remediation technologies to treat pollution in the field and farmland are compared, and the technical status and factors influencing phytomicrobial remediation of PAHs in contaminated soil are evaluated in the most comprehensive way. The mechanisms of phytomicrobial remediation of PAHs-contaminated soil under different conditions are innovatively discussed. Additionally, the regulation mechanism of enzymes involved in plant and microbial degradation of PAHs in soils is studied. This is the first study on the regulation mechanism of degradation enzyme in a PAHs review. The aim of this paper is to review the pollution status, remediation technologies, mechanisms, and biodegradation actions of PAHs in soil. This review creatively provides reliable technical support for strengthening soil remediation and environmental management.

Lei Zhao

Papers

Analysis of Factors Influencing Plant–Microbe Combined Remediation of Soil Contaminated by Polycyclic Aromatic Hydrocarbons