Effect of surfactant on phenanthrene metabolic kinetics by Citrobacter sp. SA01

Biodegradation and metabolic pathway of phenanthrene by a newly isolated bacterium Gordonia sp. SCSIO19801

The bacterium Gordonia sp. SCSIO19801, which could effectively utilize phenanthrene as the sole carbon source, was isolated from the seawater of the South China Sea. Its biodegradation characteristics, whole genome sequence, and biodegradation pathway were investigated. The phenanthrene biodegradation process of Gordonia sp. SCSIO19801 was estimated to be a first-order kinetic model with a k value of 0.26/day. Based on the identification of metabolites, utilization of probable intermediates, and genomics analysis of related genes, the degradation of phenanthrene by Gordonia sp. SCSIO19801 was proposed to occur via the salicylate metabolic pathway. This is the first report of a phenanthrene degradation pathway in Gordonia species. In addition, the Gordonia sp. SCSIO19801 could use other aromatic compounds as the sole source of carbon and energy. These characteristics indicate that Gordonia sp. SCSIO19801 can be utilized for developing effective methods for the biodegradation of petroleum hydrocarbons in marine environments.

Genetically engineered microbial remediation of soils co-contaminated by heavy metals and polycyclic aromatic hydrocarbons: Advances and ecological risk assessment

Soils contaminated with heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) have been becoming a worldwide concerned environmental problem because of threatening public healthy via food chain exposure. Thus soils polluted by HMs and PAHs need to be remediated urgently. Physical and chemical remediation methods usually have some disadvantages, e.g., cost-expensiveness and incomplete removal, easily causing secondary pollution, which are hence not environmental-friendly. Conventional microbial approaches are mostly used to treat a single contaminant in soils and lack high efficiency and specificity for combined contaminants. Genetically engineered microorganisms (GEMs) have emerged as a desired requirement of higher bioremediation efficiency for soils polluted with HMs and PAHs and environmental sustainability, which can provide a more eco-friendly and cost-effective strategy in comparison with some conventional techniques. This review comments the recent advances about successful bioremediation techniques and approaches for soil contaminated with HMs and/or PAHs by GEMs, and discusses some challenges in the simultaneous removal of HMs and PAHs from soil by designing multi-functional genetic engineering microorganisms (MFGEMs), such as improvement of higher efficiency, strict environmental conditions, and possible ecological risks. Also, the modern biotechnological techniques and approaches in improving the ability of microbial enzymes to effectively degrade combined contaminants at a faster rate are introduced, such as reasonable gene editing, metabolic pathway modification, and protoplast fusion. Although MFGEMs are more potent than the native microbes and can quickly adapt to combined contaminants in soils, the ecological risk of MFGEMs needs to be evaluated under a regulatory, safety, or costs benefit-driving system in a way of stratified regulation. Nevertheless, the innovation of genetic engineering to produce MFGEMs should be inspired for the welfare of successful bioremediation for soils contaminated with HMs and PAHs but it must be supervised by the public, authorities, and laws.

Biodegradation of phenanthrene by biodemulsifier-producing strain Achromobacter sp. LH-1 and the study on its metabolisms and fermentation kinetics

Despite many reports of the use of biodegradation to remove contaminants, the biodegradation of polycyclic aromatic hydrocarbons (PAHs) is challenging because of the hydrophobicities and low aqueous solubilities of most PAHs. In this study, phenanthrene (PHE) was used as a sole carbon and energy source to screen and identify Achromobacter sp. LH-1 for the production of biodemulsifiers that enhance the bioavailability and solubilization of PAHs. LH-1 achieved a 94% degradation rate and a 40% mineralization rate with 100 mg/L PHE. Additionally, LH-1 degraded various PAHs, and the factors that influenced the growth and PAHs degradation activity of LH-1 were not only the toxicities and structures of the substances but also the acclimation of LH-1 to these substances. Three kinetic models were used to describe the fermentation processes of cell growth, product formation and substrate degradation over time. Finally, multiple PHE degradation pathways were proposed to be utilized by strain LH-1.

Organic contamination and remediation in the agricultural soils of China: A critical review

Soil pollution is a global problem in both developed and developing countries. Countries with rapidly developing economies such as China are faced with significant soil pollution problems due to accelerated industrialization and urbanization over the last decades. This paper provides an overview of published scientific data on soil pollution across China with particular focus on organic contamination in agricultural soils. Based on the related peer-reviewed papers published since 2000 (n=203), we evaluated the priority organic contaminants across China, revealed their spatial and temporal distributions at the national scale, identified their possible sources and fates in soil, assessed their potential environmental risks, and presented the challenges in current remediation technologies regarding the combined organic pollution of agricultural soils. The primary pollutants in Northeast China were polycyclic aromatic hydrocarbons (PAHs) due to intensive fossil fuel combustion. The concentrations of organochlorine pesticides (OCPs) and phthalic acid esters (PAEs) were higher in North and Central China owing to concentrated agricultural activities. The levels of polychlorinated biphenyls (PCBs) were higher in East and South China primarily because of past industrial operations and improper electronic waste processing. The co-existence of organic contaminants was severe in the Yangtze River Delta, Pearl River Delta, and Beijing-Tianjin-Hebei Region, which are the most populated and industrialized regions in China. Integrated biological-chemical remediation technologies, such as surfactant-enhanced bioremediation, have potential uses in the remediation of soil contaminated by multiple contaminants. This critical review highlighted several future research directions including combined pollution, interfacial interactions, food safety, bioavailability, ecological effects, and integrated remediation methods for combined organic pollution in soil.