Relationship between Microbial Community Characteristics and Flooding Efficiency in Microbial Enhanced Oil Recovery

Microbial enhanced oil recovery (MEOR) is the research focus in the field of energy development as an environmentally friendly and low cost technology. MEOR can bes divided into indigenous microbial oil recovery and exogenous microbial oil recovery. The ultimate goal of indigenous microbial flooding is to enhance oil recovery via stimulation of specific indigenous microorganisms by injecting optimal nutrients. For studying the specific rule to activate the indigenous community during the long-term injection period, a series of indigenous displacement flooding experiments were carried out by using the long-core physical simulation test. The experimental results have shown that the movement of nutrients components (i.e., carbon/nitrogen/phosphorus) differed from the consumption of them. Moreover, there was a positive relationship between the nutrients concentration and bacteria concentration once observed in the produced fluid. And the trend of concentration of acetic acid was consistent with that of methanogens. When adding same activators, the impacts of selective activators to stimulate the indigenous microorganisms became worse along with the injection period, which led to less oil recovery efficiency.

Preparation,characterization,and antibacterial activity of oleic acid-grafted chitosan oligosaccharide nanoparticles

An oleic acid-grafted chitosan oligosaccharide(CSO-OA)with different degrees of amino substitution(DSs)was synthesized by the 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide(EDC)-mediated coupling reaction.Fourier transform infrared spectroscopy(FT-IR)suggested the formation of an amide linkage between amino groups of chitosan oligosaccharide and carboxyl groups of oleic acid.The critical aggregation concentrations(CACs)of CSO-OA with 6%,11%,and 21%DSs were 0.056,0.042,and 0.028 mg·mL^(-1),respectively.Nanoparticles prepared with the sonication method were characterized by means of transmission electron microscopy(TEM)and Zetasizer,and the antibacterial activity against Escherichia coli and Staphylococcus aureus was investigated.The results showed that the CSO-OA nanoparticles were in the range of 60-200 nm with satisfactory structural integrity.The particle size slightly decreased with the increase of DS of CSO-OA.The antibacterial trial showed that the nanoparticles had good antibacterial activity against E.coli and S.aureus.

The effect of carboxymethylchitosan nanoparticles on proliferation of keloid fibroblast

In this study,different molecular weight(MW)carboxymethyl chitosans(CM-chitosan)nanoparticles were prepared by ionic gelification.The particle size of nanoparticles was around 180–250 nm by dynamic light scattering(DLS)and transmission electron microscope(TEM).With the increase of CM-chitosan nanoparticles concentration from 2 to 200μg/mL,the growth inhibition effects on the keloid fibroblast increased.At the concentration of 100μg/mL,CM-chitosan nanoparticles withMW6.3 kDa had a significant inhibitory effect(inhibition ratio 48.79%)of the proliferation of keloid fibroblast.Compared with CM-chitosan solution,the inhibition of CM-chitosan nanoparticles were lower in prior period and similar in later period.By analyzing the different effects of chitosan,CM-chitosan solution and CM-chitosan nanoparticles on proliferation of keloid fibroblast,we have found that the carboxylmethyl groups of CM-chitosan play an important role in inhibition of proliferation of keloid fibroblast.