Longjiang Yu

Bio-based green composites with high performance from poly(lactic acid) and surface-modified microcrystalline cellulose

Bio-based green composites with high performance were prepared from poly(lactic acid) (PLA) and microcrystalline cellulose (MC) fibers grafted with L-lactic acid oligomers (g-MC). The chemical structure of g-MC was characterized by fourier transform infrared (FTIR) and NMR methods, which indicate that L-lactic acid oligomers were successfully grafted onto MC. The grafting percentage of L-lactic acid oligomers is ca. 3.4%, and the average degree of polymerization of grafted L-lactic acid oligomers is ca. 10%. The improved compatibility between g-MC and PLA, caused by the grafting, results in an excellent dispersion of g-MC in the composites, and consequently a considerably improved transparence of the g-MC/PLA composites compared with that of the MC/PLA composites. In addition, due to the improved compatibility between g-MC and PLA, the g-MC/PLA composites exhibit better mechanical properties than pure PLA, with a high tensile strength of 70 MPa and a higher elongation at breakage. The enhanced properties, coupled with the excellent biocompatibility and degradability, offer the bio-based composites potential applications in biomedical fields and the packaging industry.

Impact of an indigenous microbial enhanced oil recovery field trial on microbial community structure in a high pour-point oil reservoir

Based on preliminary investigation of microbial populations in a high pour-point oil reservoir, an indigenous microbial enhanced oil recovery (MEOR) field trial was carried out. The purpose of the study is to reveal the impact of the indigenous MEOR process on microbial community structure in the oil reservoir using 16Sr DNA clone library technique. The detailed monitoring results showed significant response of microbial communities during the field trial and large discrepancies of stimulated microorganisms in the laboratory and in the natural oil reservoir. More specifically, after nutrients injection, the original dominant populations of Petrobacter and Alishewanella in the production wells almost disappeared. The expected desirable population of Pseudomonas aeruginosa, determined by enrichment experiments in laboratory, was stimulated successfully in two wells of the five monitored wells. Unexpectedly, another potential population of Pseudomonas pseudoalcaligenes which were not detected in the enrichment culture in laboratory was stimulated in the other three monitored production wells. In this study, monitoring of microbial community displayed a comprehensive alteration of microbial populations during the field trial to remedy the deficiency of culture-dependent monitoring methods. The results would help to develop and apply more MEOR processes.

Microbial diversity in long-term water-flooded oil reservoirs with different in situ temperatures in China

Water-flooded oil reservoirs have specific ecological environments due to continual water injection and oil production and water recycling. Using 16S rRNA gene clone library analysis, the microbial communities present in injected waters and produced waters from four typical water-flooded oil reservoirs with different in situ temperatures of 25°C, 40°C, 55°C and 70°C were examined. The results obtained showed that the higher the in situ temperatures of the oil reservoirs is, the less the effects of microorganisms in the injected waters on microbial community compositions in the produced waters is. In addition, microbes inhabiting in the produced waters of the four water-flooded oil reservoirs were varied but all dominated by Proteobacteria. Moreover, most of the detected microbes were not identified as indigenous. The objective of this study was to expand the pictures of the microbial ecosystem of water-flooded oil reservoirs.

Bio-Fabrication of Patterned Cellulose Nano-Fibers

In this paper, a new approach for controllable bio-fabrication of patterened cellulose nano-fibers has been proposed by micro-fluidic techniques, via the combination of biological technology and nanotechnology. We attempted to make sure whether A. xylinum can regularly move within micro-fluidic channels and further to clarify how the flow can direct and control the assembly of cellulose nano-fibers. The movement of A. xylinum within the micro-fluidic channels was observed in vivo by real time video microscopy. The well-patterned materials have great potential utility in tissue engineering.

The Enhancement of Heavy Crude Oil Recovery Using Bacteria Degrading Polycyclic Aromatic Hydrocarbons

Two strains of bacteria degrading polycyclic aromatic hydrocarbons (PAHs) were isolated using enrichment cultures of various heavy crude oil samples obtained from the Dagang Oilfield. The strains, namely S17 and S28, are able to degrade crude oil using phenanthrene as the sole carbon and energy source. The crude oil composition analysis indicates both strains are able to degrade heavy hydrocarbon components in crude oil. Then, the viscosities of heavy crude oil with S17 and S28 were decreased, and the surface tension between fermentative fluid and air were also decreased. The core flooding tests demonstrated that the fermentation broth, containing the two strains, can improve the residual oil recovery ratio by approximately 12.26% after polymer flooding.

Investigation of Indigenous Microbial Enhanced Oil Recovery in a Middle Salinity Petroleum Reservoir

Culture-based techniques were applied to analyze the diversity of indigenous microbial communities in the Qinghai middle salinity petroleum reservoir (QH-MSPR). The results of the most probable number (MPN) method indicated there was an abundance of indigenous microbes (105-106MPN/ml). Two isolations (BIOS682) from the QH-MSPR were identified as Brevibacillus agri and Brevibacillus levickii. The study showed that BIOS682 enhanced the degradation rate of Huatugou crude oil. The viscosity and freezing point of crude oil after treatment by BIOS682 were all decreased. The results of TLC and FTIR spectrum analysis of the biosurfactant produced by BIOS682 indicated that it was identical to that of lipopeptide. The core-flooding tests showed that the incremental oil recoveries were 7.05-10.15%. Thus, BIOS682 may provide a viable application of microbial enhanced oil recovery (MEOR).

Preparation of Lactic Acid Based Polyurethanes Modified by Castor Oil

A series of biodegradable lactic acid based Polyurethanes modified by castor oil (PLBA-PUs) have been successfully prepared by using a two steps method as follow: Firstly prepolymers with hydroxyl terminated are synthesized by copolymerization of L-lactic acid and 1, 4-butandiol (BD), and then react with castor oil (C.O.) and hexamethylene diisocynate (HDI). The effects of BD/LA monomer ration and C.O./prepolymers mole ratio on the molecular weight and mechanical properties of PLBA-PUs are investigated. The polymers obtained are characterized by gel permeation chromatography, fourier transform infrared spectroscopy, 13C NMR, differential scanning calorimeter (DSC) and tensile testing. Their average molecular weight is over 280,000. They display excellent mechanical properties, such as a tensile strength as high as 31MPa, a tensile modulus as low as 20 MPa, and an elongation at break of 176%. Due to the biocompatibility, these PUs could find applications in biomedical fields, such as soft-tissue engineering.

Experimental Study of the Biochemistry Method for Enhancing Oil Recovery in the Oil Reservoir after Polymer Flooding

A delayed cross linked gel profile control agent is used to plug high permeable formations. Also, well nutrient fluid and microbes are injected with 50% of the heavy residual oil, after polymer flooding, in order to improve oil recovery due to the complex environment of oil reservoirs. Four strains of polycyclic aromatic hydrocarbon-degrading bacteria are selected from oilfield produced water with a high efficiency. Two of the four strains, namely BISYX17 and BISYX14, are new. Polycyclic aromatic hydrocarbon-degrading bacteria have high growth activity and they are able to reach a maximum stain concentration after being cultured 4 to 8 days, using phenanthrene as their sole carbon source. They are able to effectively degrade heavy hydrocarbon with a phenanthrene degradation rate of up to 80％, after the sample is cultured for seven days. Strain BISYX7 has the strongest phenanthrene -degrading ability, with a maximum degradation percentage of 89.89％. The strains are capable of producing dioxygenase to open rings of polycyclic aromatic hydrocarbon. The dioxygenase activity, produced by BISYX17, is able to reach 40.2 IU/mg, which is higher than the enzyme activities of a wild strain. This shows the strain has excellent potential to produce enzymes. Enzymes, produced by metabolism, have a direct degradation rate of 68% on crude oil. A core displacement simulation experiment indicates a profile control oil-displacing system is able to improve crude oil recovery efficiency by 17%, after polymer flooding. Thus, the system has excellent application potential for residual oil recovery.

Analysis of Seven Polyacrylamide(PAM)-Degrading Bacterias Using PCR-DGGE Method

Seven polyacrylamide(PAM)-degrading bacteria were isolated from waste water treated pool of Henan(P.R.China) oil field, six of which were isolated from the sample of sludge, one from the sample of waste water. Sequences and phylogenetic analysis of 16 S rDNA clones of the seven bacteria showed that four were affiliated with Actinobacteria, two with Alphaproteobacteria, one with Bacillus. PCR-DGGE profile was used to analyze the environmental dominant status of the seven bacteria. DGGE bands of five bacteria can be found in the lane of DNA from original water or sludge samples. The result provided valuable information about PAM waste treatment of He Nan Henan oil field.

Indigenous Microbial Diversity in Conglomerate Oil Reservoirs Analyzed by PCR-DGGE

Recent investigations of the microbial communities in an oil reservoir using culture-independent molecular techniques has indicated that this environment contains many uncultured assemblages, and that the cultured bacteria may represent very minor components of the true microbial diversity. In this study, 16S rDNA based PCR amplification and denaturing gradient gel electrophoresis (PCR-DGGE) was used to monitor the microbial diversity in an injection well (12#9-11) and two related production wells (12#9-9S, 13#11-8) in the KELAMAYI oilfield (Xin Jiang Autonomous Region) . The DGGE gel profiles showed significant difference between the microbial community structure of injection and production wells. The bacterial species richness in the injection well was higher than those of the production ones. Unweighted Pair Group Method Clustering (UPGMC) showed the similarity between the injection well and two production wells was 30% and 20% respectively, whereas the similarity between the two production wells was 54%. In addition, the dominant bands in the DGGE gel were excised and analyzed by nucleotide sequence analysis. This analysis of 10 excised bands showed that the dominant microorganisms in all samples had high sequence identity with rRNA genes from uncultured bacteria in the GenBank database (NCBI). Nine sequences of excised band were affiliated with alpha, gamma, delta, epsiv-Proteobacteria, and one was related to Bacteroides. Two bands exhibited 100% identity to sequences of Pseudomonas stutzeri and Aminobacter sp. cox, respectively. Three bands showed relatively low identity (92% to 93%) to cultured bacteria in the GenBank database, indicating possible new taxa. This work analyzed the composition of the microbial community in KELAMAYI oilfield, which provides important data which may facilitate the isolation of new bacteria from this special underground environment. It also provides useful information for understanding the mechanism of MEOR and applying MEOR in practical oil production in KELAMAYI oilfield.