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Hao Chen,He Tang,Xiansong Zhang,Bowen Li,Baozhen Li,Xiong Shen 한국자원공학회 2018 Geosystem engineering Vol.21 No.3
Oil quality and gas sources are two main limitations for the promotion of CO2 miscible flooding in China. However, near-miscible flooding was proposed recently which can obtain comparable recovery based on both experiments and field tests. The discovery of gas reservoir, which contains high content (24–90 mol%) of CO2 in QHD offshore oilfield, provides big potential for the implementation of CO2 flooding in China. In this paper, based on the slim tube test and slim tube simulation with denser test points, specific regions of near-miscible flooding for different CO2 contents were determined by the relation curves of displacement efficiency, IFT, and pressure. For the targeted well QHD 29-2E-5, the lower limit of CO2 content for achieving near-miscible flooding is 64%. To enlarge the scope and potential of near-miscible flooding, the feasibility of adding intermediate components (C2–C6) in the injection gas to decrease the pressure interval of near-miscible flooding was investigated. Results showed that for each 10% decrease in CO2 content, 2.5% of the intermediate components (C2–C6) of the production gas are needed to add for achieving near-miscible flooding in the well QHD 29-2E-5.
Genome Shuffling of Lactobacillus brevis for Enhanced Production of Thymidine Phosphorylase
Hongmei Li,Fang Xue,Weijie Wang,Baozhen Chen 한국생물공학회 2015 Biotechnology and Bioprocess Engineering Vol.20 No.2
Thymidine phosphorylase (TPase) plays a vital role in the biosynthesis of nucleosides and their analogs which have tremendous potential in antiviral and anticancer therapies. In this study, genome shuffling was applied to develop new strains of Lactobacillus brevis with an enhanced production of TPase. The parent organisms were mutated using ultraviolet (UV) irradiation and were shuffled by recursive pool-wise protoplast fusion. The parent protoplasts of each cycle were inactivated by UV irritation for 50 min or by heating at 60°C for 60 min. A rapid and efficient pre-screening method for determining L. brevis fusants with increased TPase production was established by adding appropriate concentrations of substrate thymidine and potassium phosphate to the culture broth based on significant differences in the absorption spectra of substrate thymidine and its product, thymine, in alkaline solution at 290 nm. Strains F3-19 and F3-36 showed high TPase activity and favorable hereditary stability and were screened out through three rounds of recursive protoplast fusion. The increase in the TPase activity of F3-19 and F3-36 was 252.6 and 260.5%, respectively, in comparison with the wild type.