Role In Phenanthrene Degradation Research Articles

Biochar prepared from Fe‐rich sludge as suitable microbial carriers for facilitating biodegradation of phenanthrene in soil

AbstractBACKGROUNDConverting waste biomass to biochar by pyrolysis is increasingly recognized as an effective waste regeneration method and could be applied in contaminated soil bioremediation. In this work, we compared the properties of three biochars (FB300, FB500 and FB700) derived from iron (Fe)‐rich sludge (FS) at 300, 500 and 700 °C, and selected FB500 as microbial carrier to evaluate its function in facilitating phenanthrene (PHE) biodegradation in soil.RESULTSIncreasing pyrolysis temperature induced a positive relationship with the ash content, pH and pore size of biochars, but a negative relationship with the yield and surface area of the biochars. FB300 and FB500 maintained more organic matter than FB700, whereas, FB500 and FB700 had greater aromatic constituents and more crystal structures than FB300. Besides, FB500 showed the strongest stability and unique magnetic properties. Thus, FB500 was selected as microbial carrier in facilitating PHE biodegradation in soil. The degradation results indicated that FB500 with bacteria immobilization played a significant role in PHE degradation; its PHE removal rate of 58.15 ± 4.90% was much higher than that of 38.73 ± 3.98% for free bacteria treatment on the first day of degradation.CONCLUSIONFe‐rich sludge can be efficiently converted into biochar that in turn can serve as microbial carrier for PHE biodegradation in contaminated soil. FB500 with bacteria immobilization was proven to promote PHE degradation. Pyrolyzing Fe‐rich sludge to biochar is a promising method for remediation of PAH‐contaminated soil. © 2021 Society of Chemical Industry (SCI).

DNA-SIP identification of phenanthrene-degrading bacteria undergoing bioaugmentation and natural attenuation in petroleum-contaminated soil

DNA-stable isotope probing (SIP) with 13C labeled phenanthrene (PHE) as substrate was used to identify specific bacterial degraders during natural attenuation (NA) and bioaugmentation (BA) in petroleum contaminated soil. BA, with the addition of a bacterial suspension mixture named GZ, played a significant role in PHE degradation with a higher PHE removal rate (∼90%) than that of NA (∼80%) during the first 3 days, and remarkably altered microbial communities. Of the five strains introduced in BA, only two genera, particularly, Ochrobactrum, Rhodococcus were extensively responsible for PHE-degradation. Six (Bacillus sp., Acinetobacter sp., Xanthomonas sp., Conexibacter sp., Acinetobacter sp. and Staphylococcus sp.) and seven (Ochrobactrum sp., Rhodococcus sp., Alkanindiges sp., Williamsia sp., Sphingobium sp., Gillisia sp. and Massilia sp.) bacteria responsible for PHE degradation were identified in NA and BA treatments, respectively. This study reports for the first time the association of Xanthomonas sp., Williamsia sp., and Gillisia sp. to PHE degradation.

Metabolic interactions in a bacterial co-culture accelerate phenanthrene degradation

A highly eff ;ective phenanthrene (PHE)-degrading co-culture containing Rhodococcus sp. WB9 and Mycobacterium sp. WY10 was constructed and completely degraded 100 mg L−1 PHE within 36 h, showing improved degradation rate compared to their monocultures. In the co-culture, strain WY10 played a predominant role in PHE degradation. 1-hydroxy-2-naphthoic acid was an end-product of PHE degradation by strain WB9 and accumulated in the culture medium to serve as a substrate for strain WY10 growth, thereby accelerating PHE degradation. In turn, strain WY10 degraded PHE and 1-hydroxy-2-naphthoic acid intracellularly to form phthalate and protocatechuate that were exported to the culture medium through efflux transporters. However, strain WY10 cannot take up extracellular phthalate due to the absence of phthalate transporters, restricting phthalate degradation and PHE mineralization. In the co-culture, phthalate and protocatechuate accumulated in the culture medium were taken up and degraded towards TCA cycle by strain WB9. Therefore, the metabolic cross-feeding of strains WB9 and WY10 accelerated PHE degradation and mineralization. These findings exhibiting the synergistic degradation of PHE in the bacterial co-culture will facilitate its bioremediation application.

Biodegradation of polycyclic aromatic hydrocarbons by a halophilic microbial consortium

In this study we investigated the phenanthrene degradation by a halophilic consortium obtained from a saline soil sample. This consortium, named Qphe, could efficiently utilize phenanthrene in a wide range of NaCl concentrations, from 1% to 17% (w/v). Since none of the purified isolates could degrade phenanthrene, serial dilutions were performed and resulted in a simple polycyclic aromatic hydrocarbon (PAH)-degrading culture named Qphe-SubIV which was shown to contain one culturable Halomonas strain and one unculturable strain belonging to the genus Marinobacter. Qphe-SubIV was shown to grow on phenanthrene at salinities as high as 15% NaCl (w/v) and similarly to Qphe, at the optimal NaCl concentration of 5% (w/v), could degrade more than 90% of the amended phenanthrene in 6days. The comparison of the substrate range of the two consortiums showed that the simplified culture had lost the ability to degrade chrysene but still could grow on other polyaromatic substrates utilized by Qphe. Metabolite analysis by HPLC and GC-MS showed that 2-hydroxy 1-naphthoic acid and 2-naphthol were among the major metabolites accumulated in the Qphe-SubIV culture media, indicating that an initial dioxygenation step might proceed at C1 and C2 positions. By investigating the growth ability on various substrates along with the detection of catechol dioxygenase gene, it was postulated that the uncultured Marinobacter strain had the central role in phenanthrene degradation and the Halomonas strain played an auxiliary role in the culture by utilizing phenanthrene metabolites whose accumulation in the media could be toxic.

Biodiversity of polycyclic aromatic hydrocarbon‐degrading bacteria from deep sea sediments of the Middle Atlantic Ridge

The bacteria involved in the biodegradation of polycyclic aromatic hydrocarbons (PAHs) in deep sea subsurface environments are largely unknown. In order to reveal their biodiversity, sediments from 2.2 m under the bottom surface at a water depth of 3542 m were sampled on the Middle Atlantic Ridge with a gravity column sampler. The sediments were promptly enriched with either crude oil or a mixture of PAHs (naphthalene, phenanthrene and pyrene) as the sole carbon source, and further enriched with the PAH mixture mentioned above in the lab. The resulting consortia were named C2CO and C2PPN respectively. Their bacterial composition was analysed with plate cultivation, PCR-DGGE and 16S rDNA library analysis. On plates, isolates belonging to Pseudoalteromonas, Halomonas, Marinobacter, Thalassospira and Tistrella dominated the culturable populations. With PCR-DGGE, five major bands closely related to Cycloclasticus, Alteromonas, Thalassospira, Alcanivorax and Rhodospirillaceae were detected in consortium C2CO, while only one major band of Cycloclasticus was detected in consortium C2PPN. In addition, the dynamics of community structure in response to aromatic substrate alterations were examined. As a result, three ribotypes of Cycloclasticus were detected by 16S rDNA library analysis, one which played a key role in phenanthrene degradation; two Alteromonas bacteria dominated the naphthalene reselected consortium. Although bacteria of the two genera grew as the main members of the communities, none of them were isolated, probably owing to their poor cultivability. These results confirm that bacteria of Cycloclasticus are important obligate PAH degraders in marine environments, and coexist with other degrading bacteria that inhabit the deep subsurface sediment of the Atlantic. This supports the view that PAH accumulation and bioattenuation occur in remote areas consistently and continuously.