Screening of lactic acid bacteria for their potential as microbial cell factories for bioconversion of lignocellulosic feedstocks

Background: The use of fossil carbon sources for fuels and petrochemicals has serious impacts on our environment and is unable to meet the demand in the future. A promising and sustainable alternative is to substitute fossil carbon sources with microbial cell factories converting lignocellulosic biomass into desirable value added products. However, such bioprocesses require availability of suitable and efficient microbial biocatalysts, capable of utilizing C5 sugars and tolerant to inhibitory compounds generated during pretreatment of biomass. In this study, the performance of a collection of lactic acid bacteria was evaluated regarding their properties with respect to the conversion of lignocellulosic feedstocks. The strains were examined for their ability to utilize xylose and arabinose as well as their resistance towards common inhibitors from pretreated lignocellulosic biomass (furan derivatives, phenolic compounds, weak acids). Results: Among 296 tested Lactobacillus and Pediococcus strains, 3 L. pentosus, 1 P. acidilactici and 1 P. pentosaceus isolates were found to be both capable of utilizing xylose and arabinose and highly resistant to the key inhibitors from chemically pretreated lignocellulosic biomass. When tested in broth with commonly found combinations of inhibitors, the selected strains showed merely 4%, 1% and 37% drop in growth rates for sugarcane bagasse, wheat straw and soft wood representatives, respectively, as compared to Escherichia coli MG1655 showing decreased growth rates by 36%, 21% and 90%, respectively, under the same conditions. Conclusion: The study showed that some strains of Lactobacilli and Pediococci have the potential to be used as production platforms for value-added products from pretreated lignocellulosic biomass. Selected Lactobacilli and Pediococci strains were able to tolerate the key inhibitors in higher concentrations compared to E. coli; in addition, as these isolates were also capable of fermenting xylose and arabinose, they constitute good candidates for efficient lignocellulosic feedstock bioconversions

Cardiac Time Intervals Measured by Tissue Doppler Imaging M-mode:Association With Hypertension, Left Ventricular Geometry, and Future Ischemic Cardiovascular Diseases

BACKGROUND: We hypothesized that the cardiac time intervals reveal reduced myocardial function in persons with hypertension and are strong predictors of future ischemic cardiovascular diseases in the general population. METHODS AND RESULTS: In a large community‐based population study, cardiac function was evaluated in 1915 participants by using both conventional echocardiography and tissue Doppler imaging (TDI). The cardiac time intervals, including the isovolumic relaxation time (IVRT), isovolumic contraction time (IVCT), and ejection time (ET), were obtained by TDI M‐mode through the mitral leaflet. IVCT/ET, IVRT/ET, and myocardial performance index [MPI=(IVRT+IVCT)/ET] were calculated. After multivariable adjustment for clinical variables the IVRT, IVRT/ET, and MPI, remained significantly impaired in persons with hypertension (n=826) compared with participants without hypertension (n=1082). Additionally, they displayed a significant dose–response relationship, between increasing severity of elevated blood pressure and increasing left ventricular mass index (P<0.001 for all). Further, during follow‐up of a median of 10.7 years, 435 had an ischemic cardiovascular disease (ischemic heart disease, peripheral arterial disease, or stroke). The IVRT/ET and MPI were powerful and independent predictors of future cardiovascular disease, especially in participants with known hypertension. They provide prognostic information incremental to clinical variables from the Framingham Risk Score, the SCORE risk chart, and the European Society of Hypertension/European Society of Cardiology risk chart. CONCLUSION: The cardiac time intervals identify impaired cardiac function in individuals with hypertension, not only independent of conventional risk factors but also in participants with a normal conventional echocardiographic examination. The IVRT/ET and MPI are independent predictors of future cardiovascular disease especially in participants with known hypertension

Predicting pK_a for proteins using COSMO-RS

We have used the COSMO-RS implicit solvation method to calculate the equilibrium constants, pKa, for deprotonation of the acidic residues of the ovomucoid inhibitor protein, OMTKY3. The root mean square error for comparison with experimental data is only 0.5 pH units and the maximum error 0.8 pH units. The results show that the accuracy of pKa prediction using COSMO-RS is as good for large biomolecules as it is for smaller inorganic and organic acids and that the method compares very well to previous pKa predictions of the OMTKY3 protein using Quantum Mechanics/Molecular Mechanics. Our approach works well for systems of about 1000 atoms or less, which makes it useful for small proteins as well as for investigating portions of larger proteins such as active sites in enzymes