The efficiencies of free and immobilized bacterial cultures of petroleum hydrocarbon degraders were evaluated and compared in this study. Hydrocarbon-degrading microbial communities with high tolerance to and high deg...The efficiencies of free and immobilized bacterial cultures of petroleum hydrocarbon degraders were evaluated and compared in this study. Hydrocarbon-degrading microbial communities with high tolerance to and high degrading ability of crude oil were obtained from the soil contaminated with crude oil in the Yellow River Delta. Then, the microbial cells were immobilized in sodium alginate （SA） beads and sodium Mginate-diatomite （SAD） beads. The biodegradation of crude oil in soil by immobilized cells was compared with that by free cells at three inoculation concentrations, 1× 104 colony forming units （cfu） kg-^（-1）（low concentration, L）, 5 × 104 cfu kg^（-1） （medium concentration, M）, and 1× 105 cfu kg^（-1） （high concentration, H）. At 20 d after inoculation, the maximum degradation rate in the immobilized systems reached 29.8% （SAD-M）, significantly higher （P 〈 0.05） than that of the free cells （21.1%）, and the SAD beads showed greater degradation than the SA beads. Moreover, both microbial populations and total microbial activity reached significantly higher level （P 〈 0.05） in the immobilized systems than free cell systems at a same initial inoculation amount. The scanning electronic microscope （SEM） images also confirmed the advantages of the immobilized microstructure of SAD beads. The enhanced degradation and bacterial growth in the SAD beads indicated the high potential of SAD beads as an effective option for bioremediation of crude oil-contaminated soils in the Yellow River Delta.展开更多
Samples of the Cambrian microbial dolomites were collected from Penglaiba section,a well-exposed stratigraphic section in the northwestern area of the Tarim Basin.This study provides an analogue for mediated dolomites...Samples of the Cambrian microbial dolomites were collected from Penglaiba section,a well-exposed stratigraphic section in the northwestern area of the Tarim Basin.This study provides an analogue for mediated dolomites that can precipitate in microbial mats and biofilms.The Cambrian stromatolitic dolomites were studied using high-resolution scanning electron microscopy.The results are as follows:(1)dolomites with 50 nm to 100 nm spherical nanostructures are aggregated into minerals of larger sphericities;(2)nanospherical dolomites of 50 nm to 170 nm diameter are densely arranged as dumbbell-shaped or chained aggregates;(3)silicified filaments,as well as dumbbell-shaped and chain arrangements,are preserved as important microstructures.On the basis of sedimentological,compositional,geochemical,and petrographic data,the microstructures were interpreted as nanoglobules that function as bacteria in the nucleation and filament mineralization stages.The microstructures function as such because they are wrapped in extracellular polymeric substance(EPS)or mucus and mineralized fossils.Silicification accounts for the exceptional preservation of microbial mat structures,including biofilms,as well as filamentous and coccoid microbes.In addition,EPS process is capable of binding different elements,with preference for Si,Mg,and Ca.Such suitable composition favors microbe mineralization and dolomite nucleation on organic substrates.These microscopic structures suggest bacterial mineralization and provide visual evidence for the origin of microbial dolomites.展开更多
基金the National Natural Science Foundation of China (No.41073067)the Key Program of the Ministry of Education,China (No.308016)the National Major Special Technological Programme Concerning Water Pollution Control and Management of China (No.2009ZX07010-008)
文摘The efficiencies of free and immobilized bacterial cultures of petroleum hydrocarbon degraders were evaluated and compared in this study. Hydrocarbon-degrading microbial communities with high tolerance to and high degrading ability of crude oil were obtained from the soil contaminated with crude oil in the Yellow River Delta. Then, the microbial cells were immobilized in sodium alginate （SA） beads and sodium Mginate-diatomite （SAD） beads. The biodegradation of crude oil in soil by immobilized cells was compared with that by free cells at three inoculation concentrations, 1× 104 colony forming units （cfu） kg-^（-1）（low concentration, L）, 5 × 104 cfu kg^（-1） （medium concentration, M）, and 1× 105 cfu kg^（-1） （high concentration, H）. At 20 d after inoculation, the maximum degradation rate in the immobilized systems reached 29.8% （SAD-M）, significantly higher （P 〈 0.05） than that of the free cells （21.1%）, and the SAD beads showed greater degradation than the SA beads. Moreover, both microbial populations and total microbial activity reached significantly higher level （P 〈 0.05） in the immobilized systems than free cell systems at a same initial inoculation amount. The scanning electronic microscope （SEM） images also confirmed the advantages of the immobilized microstructure of SAD beads. The enhanced degradation and bacterial growth in the SAD beads indicated the high potential of SAD beads as an effective option for bioremediation of crude oil-contaminated soils in the Yellow River Delta.
基金financially supported by the National Natural Science Foundation of China(Grant No.41402102)Fundamental Research Funds for the Central Universities(Grant No.2652014001)+1 种基金the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2011ZX05005–002–008HZ)National Basic Research Program of China(Grant No.2011CB201100–03)
文摘Samples of the Cambrian microbial dolomites were collected from Penglaiba section,a well-exposed stratigraphic section in the northwestern area of the Tarim Basin.This study provides an analogue for mediated dolomites that can precipitate in microbial mats and biofilms.The Cambrian stromatolitic dolomites were studied using high-resolution scanning electron microscopy.The results are as follows:(1)dolomites with 50 nm to 100 nm spherical nanostructures are aggregated into minerals of larger sphericities;(2)nanospherical dolomites of 50 nm to 170 nm diameter are densely arranged as dumbbell-shaped or chained aggregates;(3)silicified filaments,as well as dumbbell-shaped and chain arrangements,are preserved as important microstructures.On the basis of sedimentological,compositional,geochemical,and petrographic data,the microstructures were interpreted as nanoglobules that function as bacteria in the nucleation and filament mineralization stages.The microstructures function as such because they are wrapped in extracellular polymeric substance(EPS)or mucus and mineralized fossils.Silicification accounts for the exceptional preservation of microbial mat structures,including biofilms,as well as filamentous and coccoid microbes.In addition,EPS process is capable of binding different elements,with preference for Si,Mg,and Ca.Such suitable composition favors microbe mineralization and dolomite nucleation on organic substrates.These microscopic structures suggest bacterial mineralization and provide visual evidence for the origin of microbial dolomites.
