100 research outputs found

    Alleviation of carbon catabolite repression in Enterobacter aerogenes for efficient utilization of sugarcane molasses for 2,3-butanediol production

    Get PDF
    Table S3. Comparison of fed-batch fermentation with EMY-01, EMY-68, EMY-70S, and EMY-70SP using sugarcane molasses

    Production of 2,3-butanediol in Saccharomyces cerevisiae by in silico aided metabolic engineering

    Get PDF
    BACKGROUND: 2,3-Butanediol is a chemical compound of increasing interest due to its wide applications. It can be synthesized via mixed acid fermentation of pathogenic bacteria such as Enterobacter aerogenes and Klebsiella oxytoca. The non-pathogenic Saccharomyces cerevisiae possesses three different 2,3-butanediol biosynthetic pathways, but produces minute amount of 2,3-butanediol. Hence, we attempted to engineer S. cerevisiae strain to enhance 2,3-butanediol production. RESULTS: We first identified gene deletion strategy by performing in silico genome-scale metabolic analysis. Based on the best in silico strategy, in which disruption of alcohol dehydrogenase (ADH) pathway is required, we then constructed gene deletion mutant strains and performed batch cultivation of the strains. Deletion of three ADH genes, ADH1, ADH3 and ADH5, increased 2,3-butanediol production by 55-fold under microaerobic condition. However, overproduction of glycerol was observed in this triple deletion strain. Additional rational design to reduce glycerol production by GPD2 deletion altered the carbon fluxes back to ethanol and significantly reduced 2,3-butanediol production. Deletion of ALD6 reduced acetate production in strains lacking major ADH isozymes, but it did not favor 2,3-butanediol production. Finally, we introduced 2,3-butanediol biosynthetic pathway from Bacillus subtilis and E. aerogenes to the engineered strain and successfully increased titer and yield. Highest 2,3-butanediol titer (2.29 g·l(-1)) and yield (0.113 g·g(-1)) were achieved by Δadh1 Δadh3 Δadh5 strain under anaerobic condition. CONCLUSIONS: With the aid of in silico metabolic engineering, we have successfully designed and constructed S. cerevisiae strains with improved 2,3-butanediol production

    The Structure of the Cataract-Causing P23T Mutant of Human γD-Crystallin Exhibits Distinctive Local Conformational and Dynamic Changes†,‡

    Get PDF
    Crystallins are major proteins of the eye lens and essential for lens transparency. Mutations and aging of crystallins cause cataracts, the predominant cause of blindness in the world. In human γD-crystallin, the P23T mutant is associated with congenital cataracts. Until now, no atomic structural information has been available for this variant. Biophysical analyses of this mutant protein have revealed dramatically reduced solubility compared to that of the wild-type protein due to self-association into higher-molecular weight clusters and aggregates that retain a nativelike conformation within the monomers [Pande, A., et al. (2005) Biochemistry 44, 2491−2500]. To elucidate the structure and local conformation around the mutation site, we have determined the solution structure and characterized the protein’s dynamic behavior by NMR. Although the global structure is very similar to the X-ray structure of wild-type γD-crystallin, pivotal local conformational and dynamic differences are caused by the threonine substitution. In particular, in the P23T mutant, the imidazole ring of His22 switches from the predominant Nε2 tautomer in the wild-type protein to the Nδ1 tautomer, and an altered motional behavior of the associated region in the protein is observed. The data support structural changes that may initiate aggregation or polymerization by the mutant protein.National Institutes of Health (U.S.) (Grant GM 17980)National Eye Institute (Grant EY 015834

    Deployable Hook Retrieval System for UAV Rescue and Delivery

    Get PDF
    The rapid development of unmanned aerial vehicles (UAVs) has helped expand their practical use to many industrial applications. However, UAVs sometimes suffer from a flight time limitation and/or a loss in communication. Such undesired malfunctions can endanger public safety and incur economic losses. This paper presents a new class of UAV that can retrieve a disabled or malfunctioned UAV from the ground. We developed a deployable hook retrieval system (DHRS) which integrates three principal mechanisms (i.e., deployment, slider-linkage-release, and hook release). Each mechanism plays a role in deploying and retrieving multiple hooks while using a simple control strategy. Through a Finite Element Method simulation, the hook was topologically optimized in order to achieve a high strength while reducing weight. The deployed multiple hooks allow the device to capture the target regardless of its orientation. Due to these design strategies, object recognition using a computer vision was simply demonstrated by exploiting ORB and FLANN algorithms. Through an experimental study, we discussed the target range, success rate, and the practical uses that the DHRS could achieve. The results show that the proposed designs were versatile and consistently successful in capturing the targets while addressing constraints such as power consumption, computational load, and lack of prior knowledge or information about the target

    A case of levocetirizine-induced liver injury

    Get PDF
    Levocetirizine is a second-generation nonsedative antihistaminic agent that has been demonstrated to be safe and effective for treating allergic disease. There was only one case report of levocetirizine-induced liver toxicity, but a liver biopsy was not performed. In this article, we present the first case of levocetirizine-induced liver injury with histologic findings. A 48-year-old man was hospitalized with jaundice and generalized pruritus that had developed after 2 months of therapy with levocetirizine for prurigo nodularis. Laboratory findings revealed acute hepatitis with cholestasis. A liver biopsy demonstrated portal inflammation and hepatitis with apoptotic hepatocytes. The patient fully recovered 3 weeks after withdrawing levocetirizine. Although levocetirizine is safe and effective, physicians should be aware of its potential hepatotoxicity

    Small Molecule Inhibition of HIV-1–Induced MHC-I Down-Regulation Identifies a Temporally Regulated Switch in Nef Action

    Get PDF
    Nef assembles a multi-kinase complex triggering MHC-I down-regulation. We identify an inhibitor that blocks MHC-I down-regulation, identifying a temporally regulated switch in Nef action from directing MHC-I endocytosis to blocking cell surface delivery. These findings challenge current dogma and reveal a regulated immune evasion program

    Identification and Functional Analysis of Light-Responsive Unique Genes and Gene Family Members in Rice

    Get PDF
    Functional redundancy limits detailed analysis of genes in many organisms. Here, we report a method to efficiently overcome this obstacle by combining gene expression data with analysis of gene-indexed mutants. Using a rice NSF45K oligo-microarray to compare 2-week-old light- and dark-grown rice leaf tissue, we identified 365 genes that showed significant 8-fold or greater induction in the light relative to dark conditions. We then screened collections of rice T-DNA insertional mutants to identify rice lines with mutations in the strongly light-induced genes. From this analysis, we identified 74 different lines comprising two independent mutant lines for each of 37 light-induced genes. This list was further refined by mining gene expression data to exclude genes that had potential functional redundancy due to co-expressed family members (12 genes) and genes that had inconsistent light responses across other publicly available microarray datasets (five genes). We next characterized the phenotypes of rice lines carrying mutations in ten of the remaining candidate genes and then carried out co-expression analysis associated with these genes. This analysis effectively provided candidate functions for two genes of previously unknown function and for one gene not directly linked to the tested biochemical pathways. These data demonstrate the efficiency of combining gene family-based expression profiles with analyses of insertional mutants to identify novel genes and their functions, even among members of multi-gene families

    Thermal Evaluation of a Novel Integrated System Based on Solid Oxide Fuel Cells and Combined Heat and Power Production Using Ammonia as Fuel

    Full text link
    A novel integrated system based on solid oxide fuel cells (SOFCs), a gas turbine (GT), the steam Rankine cycle (SRC), the Kalina cycle (KC), and the organic Rankine cycle (ORC) is proposed to achieve cascade energy utilization. Mathematical models are introduced and system performance is analyzed using energy and exergy methods. The first and second laws of thermodynamics are used to analyze the system thermodynamically. In addition, exergy destruction and losses of the various integrated subsystems are calculated. The energy and exergy efficiencies of the multigeneration system are estimated to be 60.4% and 57.3%, respectively. In addition, the hot water produced during the waste heat recovery process may also be used for accommodating seafarers on ships. Sequential optimization is developed to optimize the operating conditions of the integrated system to achieve the required power output. A comprehensive parametric study is conducted to investigate the effect of varying the current densities of the fuel cell and working fluid of the ORC on the overall performance of the combined system and subsystems. The working performance of five working fluids for the ORC as candidates—R134a, R600, R601, R152a, and R124—is compared. R152a, which provides 71.23 kW of power output, and energy and exergy efficiencies of 22.49% and 42.76%, respectively, is selected as the best thermodynamic performance for the ORC
    corecore