Effects of biosurfactants produced by Candida antarctica on the biodegradation of petroleum compounds

The effects of biosurfactants on the biodegradation of petroleum compounds were investigated. Candida antarctica T-34 could produce extracellular biosurfactant mannosylerythritol lipids (MELs) when it was cultured in vegetable oil. In addition, in our previous study, it was found that this strain could also produce a new type of biosurfactant while it grew on n-undecane (C₁₁H₂₄), and the biosurfactant was named as BS-UC. In flask culture of Candida antarctica, the addition of BS-UC could improve the biodegradation rate of some n-alkanes (e.g. 90.2% for n-decane, 90.2% for n-undecane, 89.0% for dodecane), a mixture of n-alkanes (82.3%) and kerosene (72.5%). By comparing the effects of the biosurfactants BS-UC and MEL and chemical surfactants on the biodegradation of crude oil, it was found that biosurfactants could be used to enhance the degradation of petroleum compounds instead of chemical surfactants. In a laboratory scale immobilized bioreactor, the addition of biosurfactant improved not only the emulsification of kerosene in simulated wastewater but also its biodegradation rate. The highest degradation rate of kerosene by addition of MEL and BS-UC reached 87 and 90% at 15 h, respectively. The results showed that the biosurfactant BS-UC was highly promising for work on biodegradation of hydrophobic contaminants.     

小叶白蜡接种外生菌根真菌对土壤石油烃的降解效果

采用盆栽实验研究了小叶白蜡(Fraxinus sogdiana)接种4种外生菌根真菌(E1-毛边滑锈伞(Hebeloma mesophaeusm)、E2-劣味乳菇(Lactarius insulsns)、E3-松塔牛肝菌(Stro-bilomyces floccopus)和E4-丝膜菌(Cortinarius russus)对沈抚灌区土壤石油烃的降解效果。结果表明:在白蜡不同组合双接种及混合接种中,以混合接种对土壤石油烃的降解效果最好,降解率比对照提高23.6%;其次为双接种中的E1E3和E2E4组合,降解率分别比对照提高21.0%和12.7%。接种外生菌根真菌可促进白蜡生长,尤其可明显提高其根生物量,增加侧根数,接种E1E3、E2E4和混合菌使白蜡侧根数分别增加了100%、67%和81%。相关分析表明,石油烃降解率与白蜡的侧根数呈显著相关,可能是其降解率提高的主要原因。     

海洋石油污染物的微生物降解与生物修复

石油是海洋环境的主要污染物 ,已经对海洋及近岸环境造成了严重的危害。微生物降解是海洋石油污染去除的主要途径。海洋石油污染物的微生物降解受石油组分与理化性质、环境条件以及微生物群落组成等多方面因素的制约 ,N和P营养的缺乏是海洋石油污染物生物降解的主要限制因子。在生物降解研究基础上发展起来的生物修复技术在海洋石油污染治理中发展潜力巨大 ,并且取得了一系列成果。介绍了海洋中石油污染物的来源、转化过程、降解机理、影响生物降解因素及生物修复技术等方面内容 ,强调了生物修复技术在治理海洋石油污染环境中的优势和重要性 ,指出目前生物修复技术存在的问题。     

Remediation of Nitrogen-Contaminated Sediment Using Bioreactive,Thin-layer Capping with Biozeolite

In situ amendment of nitrogen-contaminated sediment using bioreactive, thin-layer capping (BTC) with biozeolite (i.e., zeolite with heterotrophic nitrifiers as well as aerobic denitrifiers attached) was studied herein. BTC with biozeolite for nitrogen-contaminated sediment management was evaluated through long-term (170 days) sediment incubation laboratory experiments. The results showed that BTC with relatively small dose rates (<10 kg m^?2) of biozeolite reduced the total nitrogen (TN) concentration in overlying water by over 90%, so it was effective in reducing the amount of N released from sediment. Higher-dose rates of biozeolite capping achieved an even higher removal efficiency. With the DO concentration of 1.5 ～ 6.5 mg L^?1 in overlying water, the reduction efficiency of TN in overlying water using BTC was higher than that less than 1 mg L^?1. In BTC systems, biological regeneration (i.e., heterotrophic nitrifiers attached to zeolite can regenerate the zeolite ion exchange capacity for ammonium) occurred in biozeolite which was saturated with ammonium during the nitrification period. In addition, TN contents in surface sediment in BTC systems were reduced at different levels after the experiment. These findings indicate that the BTC can be a feasible remedial approach to reduce N in overlying water and sediment in eutrophic water bodies. In the BTC, N load was reduced by the added biozeolite through adsorbing ammonium (NH₄⁺-N), converting NH₄⁺-N into nitrate nitrogen (NO₃^?-N) and nitrogen gas (N₂), and assimilating inorganic nitrogen.     

石香薷挥发油提取的比较研究

利用GC-MS对石香薷挥发油进行了定性、定量分析。采取超临界CO2萃取、水蒸气蒸馏和有机溶剂石油醚萃取这三种方法提取石香薷挥发油。这三种方法提取石香薷挥发油的主要成分基本相似,主要为含氧化合物(香薷酮、百里香酚和香荆芥酚)等,采取超临界CO2萃取和水蒸气蒸馏的石香薷挥发油品质较优。超临界CO2萃取法为提取石香薷挥发油的理想方法。     

Comparison of Extractants for Removing Heavy Metals from Contaminated Clayey Soils

This article describes the removal of heavy metals from contaminated clayey soils by soil washing using various extractants. Two clayey soils, kaolin, a low buffering soil with pH of 5, and glacial till, a high buffering soil with pH of 8, were used to represent various soil conditions. These soils were spiked with chromium (Cr), nickel (Ni), and cadmium (Cd) to simulate improper disposal of typical electroplating waste constituents. The following extracting solutions were investigated for the removal of heavy metals from the soils: deionized water, distilled water, and tap water; acetic acid and phosphoric acid; chelating agents ethylenediaminetetraacetic acid (EDTA) and citric acid; and the oxidizing agents potassium permanganate and hydrogen peroxide. The effect of extractant concentration on removal of heavy metals was also investigated. Complete removal of Cr was achieved using 0.1?M potassium permanganate for kaolin, while a maximum of 54% was removed from glacial till. A maximum Ni removal of 80% was achieved using tapwater for kaolin, while a maximum removal of 48 to 52% was achieved using either 1?M acetic acid or 0.1?M citric acid for glacial till. A maximum Cd removal of 50% was achieved using any of the extractants for kaolin, while a maximum removal of 45 to 48% was obtained using either acids or chelating agents for glacial till. Overall, this study showed that complete removal of Cr, Ni, and Cd from clayey soils is difficult to achieve using the soil-washing process, and also the use of one extractant may not be effective in removing all metals. A sequential extraction using different extractants may be needed for the removal of multiple metal contaminants from clayey soils.     

Purification and characterization of a highly active chromate reductase from endophytic Bacillus sp. DGV19 of Albizzia lebbeck (L.) Benth. actively involved in phytoremediation of tannery effluent-contaminated sites

Phytoremediation using timber-yielding tree species is considered to be the most efficient method for chromium/tannery effluent-contaminated sites. In this study, we have chosen Albizzia lebbeck, a chromium hyperaccumulator plant, and studied one of its chromium detoxification processes operated by its endophytic bacterial assemblage. Out of the four different groups of endophytic bacteria comprising Pseudomonas, Rhizobium, Bacillus, and Salinicoccus identified from A. lebbeck employed in phytoremediation of tannery effluent-contaminated soil, Bacillus predominated with three species, which exhibited not only remarkable chromium accumulation ability but also high chromium reductase activity. A chromate reductase was purified to homogeneity from the most efficient chromium accumulator, Bacillus sp. DGV 019, and the purified 34.2-kD enzyme was observed to be stable at temperatures from 20°C to 60°C. The enzyme was active over a wide range of pH values (4.0–9.0). Furthermore, the enzyme activity was enhanced with the electron donors NADH, followed by NADPH, not affected by glutathione and ascorbic acid. Cu²⁺ enhanced the activity of the purified enzyme but was inhibited by Zn²⁺ and etheylenediamine tetraacetic acid (EDTA). In conclusion, due to its versatile adaptability the chromate reductase can be used for chromium remediation.     

Phytoremediation of fuel oil and lead co-contaminated soil by Chromolaena odorata in association with Micrococcus luteus

Phytoremediation is widely promoted as a cost-effective technology for treating heavy metal and total petroleum hydrocarbon (TPH) co-contaminated soil. This study investigated the concurrent removal of TPHs and Pb in co-contaminated soil (27,000 mg kg^?1 TPHs, 780 mg kg^?1 Pb) by growing Siam weed (Chromolaena odorata) in a pot experiment for 90 days. There were four treatments: co-contaminated soil; co-contaminated soil with C. odorata only; co-contaminated soil with C. odorata and Micrococcus luteus inoculum; and co-contaminated soil with M. luteus only. C. odorata survived and grew well in the co-contaminated soil. C. odorata with M. luteus showed the highest Pb accumulation (513.7 mg kg^?1) and uptake (7.7 mg plant^?1), and the highest reduction percentage of TPHs (52.2%). The higher TPH degradation in vegetated soils indicated the interaction between the rhizosphere microorganisms and plants. The results suggested that C. odorata together with M. luteus and other rhizosphere microorganisms is a promising candidate for the removal of Pb and TPHs in co-contaminated soils.     

Bioremediation of Diesel-contaminated Soil by Composting with Locally Generated Bulking Agents

Herein, we conducted a study toward understanding the impact of composting of the diesel-contaminated soil with some locally available bulking agents (rice husks (RHs), sawdust (SD), and wood chips (WCs)). In order to ascertain the effectiveness of petroleum degradation by the process assayed, we compared the protocols with monitored natural attenuation (MNA). The overall degradation pattern was modeled with non-linear regression by comparing the experimental data with first and second-order kinetic equations. At the end of the six-week study, the amount of total petroleum hydrocarbon removed from contaminated soil was 98.26 ± 1.33% (amendment with SD + RHs + WCs), 96.89 ± 1.20 (RHs amendment), 96.55 ± 1.29% (amendment with SD), 90.01 ± 0.22% (WCs amendment), and 85.02 ± 0.21% (MNA). The degradation of TPH trends followed a second-order kinetic model for all the four compost treatments while the MNA was found to follow a first-order (slower) degradation pattern. In general, the results of the parameter estimate showed that amendment with mixture of the three bulking agents was 1.08 (8%) slower (k₂ = (1.289 ± 0.16) × 10^?5 (g mg^?1 d^?1), r² = 0.991) than SD amendment alone (k₂ = (1.392 ± 0.14) × 10^?5 (g mg^?1 d^?1), r² = 0.995). However, the mixture of the bulking agents was found to be 1.67, 1.41, and 2.4 times faster than amendments with WCs, rice, and MNA, respectively. The phytotoxicity test revealed that all the compost treatments except WCs resulted in germination index of ≥80% after six weeks of bioremediation tests. The outcome of the current investigation confirms the effectiveness of bulking agents (especially when combined) in the supply of nutrients for the bioremediation of diesel-impacted soil.