A combined approach of physicochemical and biological methods for the characterization of petroleum hydrocarbon-contaminated soil

Main physicochemical and microbiological parameters of collected petroleum-contaminated soils with different degrees of contamination from DaGang oil field (southeast of Tianjin, northeast China) were comparatively analyzed in order to assess the influence of petroleum contaminants on the physicochemical and microbiological properties of soil. An integration of microcalorimetric technique with urease enzyme analysis was used with the aim to assess a general status of soil metabolism and the potential availability of nitrogen nutrient in soils stressed by petroleum-derived contaminants. The total petroleum hydrocarbon (TPH) content of contaminated soils varied from 752.3 to 29,114 mg kg^?1. Although the studied physicochemical and biological parameters showed variations dependent on TPH content, the correlation matrix showed also highly significant correlation coefficients among parameters, suggesting their utility in describing a complex matrix such as soil even in the presence of a high level of contaminants. The microcalorimetric measures gave evidence of microbial adaptation under highest TPH concentration; this would help in assessing the potential of a polluted soil to promote self-degradation of oil-derived hydrocarbon under natural or assisted remediation. The results highlighted the importance of the application of combined approach in the study of those parameters driving the soil amelioration and bioremediation.     

Functional gene expression of oil-degrading bacteria resistant to hexadecane toxicity

Contamination with oil poses a threat to the environment and to human health worldwide. Biological methodologies have proved to be economical, versatile and efficient for the remediation of pollutants. In this paper, a highly efficient oil-degrading bacterial strain USTB-2 was isolated from an oil production well of Dagang oil field in Tianjin, China. The 16S rRNA sequence of USTB-2 showed 100% similarity with that of Bacillus subtilis BSn5. Hexadecane is one of the most important components in petroleum. The half inhibitory ratio (IC₅₀) of hexadecane inhibited organisms, determined by microcalorimetry, was lower in USTB-2 than in B. BSn5. The results indicate that the strain USTB-2 degrades hexadecane to make it less toxic compared with the normal strain. RT-PCR was used to evaluate the expression of oil-degrading enzymes, specifically 4-hydroxyphenylacetate 3-monooxygenase genes (HPMO). A sharp increase in the expression of HPMO genes was observed for USTB-2, while the expression of HPMO genes in reference strain B. BSn5 remained relatively stable. These methods can be used to study the metabolic potential of microorganisms for in situ oil decontamination.     

Influence of synthetic surfactants on the uptake of Pd, Cd and Pb by the marine macroalga, Ulva lactuca

Uptake of Pd, Cd and Pb by the marine macroalga, Ulva lactuca, has been studied in the presence of an anionic (sodium dodecyl sulphate, SDS), cationic (hexadecyltrimethylammonium bromide; HDTMA) and non-ionic (Triton X-100; TX) surfactant. Compared with the surfactant-free system, metal sorption was reduced in the presence of SDS or TX. Neither surfactant, however, had any measurable impact on cell membrane permeability, determined by leakage of dissolved free amino acids (DFAA), or on metal internalisation. We attribute these observations to the stabilisation of aqueous Cd and Pb by SDS and the shielding of otherwise amenable sorption sites by TX. Presence of HDTMA resulted in a reduction in the extent of both sorption and internalisation of all metals and a significant increase in the leakage of DFAA. Thus, by enhancing membrane permeability, HDTMA exerts the greatest influence on metal behaviour in the presence of U. lactuca.     

Isolation and characterization of a newly isolated pyrene-degrading Acinetobacter strain USTB-X

The pryene-degradation bacterium strain USTB-X was newly isolated from the polycyclic aromatic hydrocarbon (PAH)-contaminated soil in Beijing Coking Plant, China. The strain was identified as Acinetobacter with respect to its 16S rDNA and morphological and physiological characteristics. The strain was Gram-negative, non-mobile, non-acid-fast, and non-spore-forming, short rods in young culture and 0.8–1.6 μm in diameter and 1.2–2.5 μm long in the stationary phase of growth. Strain USTB-X could utilize pyrene, naphthalene, fluorene, phenanthrene, benzene, toluene, ethylbenzene, ethanol, methanol, and Tween 80 as sole source of carbon and energy. The strain could produce biosurfactants which enhanced the removal of pyrene and could remove 63 % of pyrene with an initial concentration of 100 mg·L^?1 in 16 days without other substrates. Based on the intermediates analyzed by gas chromatography-mass spectrometry, we also deduced the possible metabolic pathway of strain USTB-X for pyrene biodegradation. Results indicated that the strain USTB-X had high potential to enhance the removal of PAHs in contaminated sites.     

Short-term effect of aniline on soil microbial activity: a combined study by isothermal microcalorimetry, glucose analysis, and enzyme assay techniques

The accidents of aniline spill and explosion happened almost every year in China, whereas the toxic effect of aniline on soil microbial activity remained largely unexplored. In this study, isothermal microcalorimetric technique, glucose analysis, and soil enzyme assay techniques were employed to investigate the toxic effect of aniline on microbial activity in Chinese soil for the first time. Soil samples were treated with aniline from 0 to 2.5 mg/g soil to tie in with the fact of aniline spill. Results from microcalorimetric analysis showed that the introduction of aniline had a significant adverse effect on soil microbial activity at the exposure concentrations ≥0.4 mg/g soil (p?<?0.05) and ≥0.8 mg/g soil (p?<?0.01), and the activity was totally inhibited when the concentration increased to 2.5 mg/g soil. The glucose analysis indicated that aniline significantly decreased the soil microbial respiratory activity at the concentrations ≥0.8 mg/g soil (p?<?0.05) and ≥1.5 mg/g soil (p?<?0.01). Soil enzyme activities for β-glucosidase, urease, acid-phosphatase, and dehydrogenase revealed that aniline had a significant effect (p?<?0.05) on the nutrient cycling of C, N, and P as well as the oxidative capacity of soil microorganisms, respectively. All of these results showed an intensively toxic effect of aniline on soil microbial activity. The proposed methods can provide toxicological information of aniline to soil microbes from the metabolic and biochemical point of views which are consistent with and correlated to each other.