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Steady and Dynamic Rheological Properties of Thickened Beverages Used for Dysphagia Diets
조현문,Whachun Yoo,유병승 한국식품과학회 2012 Food Science and Biotechnology Vol.21 No.6
Thickened beverages prepared with commercial food thickeners are widely used to promote safer and more successful swallowing in patients with dysphagia. In this study, the rheological properties of cold thickened beverages (bottled water, orange juice, apple juice, and whole milk)prepared with a commercially available gum-based food thickener (xanthan-guar gum mixture) marketed in Korea were investigated at 3 different thickener concentrations (2,3, and 4%, w/w). Thickened beverages showed high shearthinning (n=0.12-0.21) behavior with Casson yield stress at all concentrations. Their apparent viscosity (ηa,50),consistency index (K), Casson yield stress (σoc), storage modulus (G'), and loss modulus (G") increased with an increase in thickener concentration. Steady and dynamic rheological parameters also demonstrated greater differences in rheological behaviors between thickened beverages with different thickener concentrations. These results suggest that rheological properties of thickened beverages are strongly affected by thickener concentration and the type of beverage prepared.
Optimization of central metabolism for itaconate production from acetate
문조현,노명현,우성화,임현규,정규열 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
Utilization of acetate, abundant and cheap carbon sources, can effectively reduce the production cost and enhance the economic feasibility. In this study, we engineered an Escherichia coli strain to produce itaconic acid from acetate. We initially screened for a strain with a high tolerance to 10 g/L of acetate in the medium, and the W strain was selected as the host. Subsequently, the WC strain was obtained by overexpression of cis-aconitate decarboxylase using a synthetic promoter and 5′ UTR. As the WC strain produced only 0.13 g/L itaconic acid because of low acetate uptake, the acetate assimilating pathway and glyoxylate shunt pathway were amplified by overexpression of pathway genes as well as its deregulation. The resulting strain, WCIAG4 produced 3.57 g/L itaconic acid after 88 h of fermentation with rapid acetate assimilation. These efforts support that acetate can be a potential feedstock for biochemical production with engineered E. coli.
문조현,노명현,정규열 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
Abundant and cheap carbon sources can effectively reduce the production cost and enhance the economic feasibility. Previously conversion of acetate into itaconate was conducted with rational metabolic engineering strategy, proving the potential of acetate as a promising carbon source. In this study, we applied combinatorial approach to further enhance the production from acetate. Initially, the itaconate-specific screening device was constructed using recently characterized transcriptional regulator. The selective growth was validated in accordance with the addition of itaconate. Thereafter, Adaptive Laboratory Evolution was repeated over several rounds and the increase in growth rate was observed under the selection pressure. The evolved strain could produce 1.06 g/L of itaconate, a 1.24-fold increase in comparison with parental strain and the yield could be significantly enhanced by 7.16-fold.