Thermal Adaptation of Dihydrofolate Reductase from the Moderate ThermophileGeobacillus stearothermophilus

The thermal melting temperature of dihydrofolate reductase from Geobacillus stearothermophilus (BsDHFR) is 30 °C higher than that of its homologue from the psychrophile Moritella profunda. Additional proline residues in the loop regions of BsDHFR have been proposed to enhance the thermostability of BsDHFR, but site-directed mutagenesis studies reveal that these proline residues contribute only minimally. Instead, the high thermal stability of BsDHFR is partly due to removal of water-accessible thermolabile residues such as glutamine and methionine, which are prone to hydrolysis or oxidation at high temperatures. The extra thermostability of BsDHFR can be obtained by ligand binding, or in the presence of salts or cosolvents such as glycerol and sucrose. The sum of all these incremental factors allows BsDHFR to function efficiently in the natural habitat of G. stearothermophilus, which is characterized by temperatures that can reach 75 °C

Determinants of Corporate Hedging: A (Statistical) Meta-Analysis

International audienceWhile literature provides several hedging theories, evidence on the corporate incentives to hedge remains ambiguous. We synthesize data of empirical studies via statistical meta-analysis to test different hedging hypotheses. To our knowledge, this constitutes the first application of such a methodology in financial economics. Our results imply that financial distress costs induce firms to hedge. We find weak evidence that the underinvestment problem and the dependence on costly external financing influence hedging behavior. Taxes and agency conflicts do not show explanatory power. Because statistical and narrative reviews yield different outcomes, we see various other application possibilities for meta-analysis in financial economics

What do we really know about the influence of environmental on financial performance? A meta-regression analysis (MRA)

International audienceno abstrac

Measurement matters – A meta-study of the determinants of corporate capital structure

International audienceThis study aggregates the mixed empirical evidence of the seven most commonly investigated determinants of corporate capital structure. We apply meta-regression analysis on a data set of 3,890 reported results, manually collected from 100 primary studies. Our results reveal that − in descending order of importance − tangible assets (positive sign), market-to-book ratio (negative sign), and profitability (negative sign) are significant determinants of corporate debt level. In addition, we find evidence for publication selection bias in academic literature. Accordingly, specific results are systematically overrepresented, as authors prefer reporting statistically significant estimates in line with theory or existing empirical results. Significant determinants, as well as publication selection bias, are more pronounced for characteristics like market-based measures of capital structure, total debt measures of capital structure, and for top articles in highly renowned journals, compared to book-based measures of capital structure or long-term debt measures of capital structure or randomly selected articles including more unknown and unpublished studies

What do we really know about corporate hedging? A multimethod meta-analytical study

International audienceno abstrac

What do we really know about corporate hedging? A multimethod meta-analytical study

International audienceThis paper employs meta-analysis to aggregate and systematically analyze the mixed empirical evidence on the determinants of corporate hedging reported in 132 previously published studies covering data from more than 73,000 firms. Among the fourteen proxy variables analyzed by multivariate meta-analysis, three variables emerge as reliable explanatory factors for corporate hedging decisions supporting the bankruptcy and financial distress hypothesis: dividend yield (positive sign), liquidity (negative sign), and firm size (positive sign). Moreover, for tax-loss carry forwards (positive sign) and research and development (positive sign), our findings indicate a weak impact on corporate hedging behavior reflecting tax reasons, the coordination between financing and investment, and agency conflicts between shareholders and debtholders. Regarding the asymmetric information and agency conflicts of equity hypothesis, we find no explanatory power. The further analysis of heterogeneity via meta-regression reveals several factors that determine the mixed empirical evidence reported in previous studies. First, the results indicate that studies analyzing firms from North America report, on average, a lower impact of leverage on the corporate hedging decision. Moreover, studies examining more recent data samples tend to find a weaker relation between tangible assets and hedging, R&D and hedging, respectively. Overall, our results encourage scientific research to put more emphasis on finer-grained examinations of hedging variations and to discover rationales of corporate hedging extending classical financial theories

Fundamental research enables process optimization in the sugar Industry

Storing sugar extracts as thick juice, a form of sucrose syrup, is common practice in the sugar industry. However, this thick juice storage commonly faces problems due to juice degradation. The precise cause for this problem was ill defined but believed to be of microbial origin. In this research, the microbial population dynamics during thick juice storage was described and we identified the causative degradation flora. Finally, optimal good storage practices were defined with the ultimate goal of preventing thick juice degradation. The thick juice microflora has been thoroughly studied with both culture-based and culture-independent techniques, encompassing the application of 16S rRNA gene clone libraries and T-RFLP analysis, providing a more comprehensive representation of the thick juice microflora than the previous studies. The initial, heterogeneous microflora in freshly produced thick juice evolved to the dominance (>99%) of Tetragenococcus halophilus during storage. Based on its high population density (106–107 cfu/ml), the ability to consume sucrose and the similar acidification pattern of experimentally infested thick juice, T. halophilus is proposed to be the key player in thick juice degradation. Remarkably, T. halophilus has thus far been associated only with high salt food products and our work is the first to associate it with high sugar matrices. In addition to T. halophilus, other bacteria such as Staphylococcus and Bacillus species were consistently present, though in lower steady concentrations of 103 cfu/ml. In order to be able to detect the different bacteria that may occur in thick juice, a DNA array was developed containing detector oligonucleotides for the genera Bacillus, Kocuria, Staphylococccus and Tetragenococcus, and the species Aerococcus viridans, Leuconostoc mesenteroides and T. halophilus. The developed macroarray was shown reliable and sensitive (up to 102 cfu/ml) and has potential for monitoring the thick juice microflora during storage as an early warning system. Finally, best available storage practices were defined based on laboratory and pilot scale storage experiments using the independent variables solids content, pH, storage temperature and biocide concentration. In conclusion, this work has contributed to a better description of the microbial population dynamics during thick juice storage and degradation, and to the definition of improved storage practices that will be useful for the sugar industry.status: publishe