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Miguel A. De la Cruz,Miguel A. Ares,Diana Rodríguez-Valverde,Alba Adriana Vallejo-Cardona,Mario Alberto Flores-Valdez,Iris Denisse Cota Núñez,Michel de Jesús Aceves-Sánchez,Jonahtan Lira-Chávez,Jacobo 한국미생물·생명공학회 2020 Journal of microbiology and biotechnology Vol.30 No.6
Mycobacterium tuberculosis produces mycolic acids which are relevant for persistence, recalcitrance to antibiotics and defiance to host immunity. c-di-GMP is a second messenger involved in transition from planktonic cells to biofilms, whose levels are controlled by diguanylate cyclases (DGC) and phosphodiesterases (PDE). The transcriptional regulator dosR, is involved in response to low oxygen, a condition likely happening to a subset of cells within biofilms. Here, we found that in M. bovis BCG, expression of both BCG1416c and BCG1419c genes, which code for a DGC and a PDE, respectively, decreased in both stationary phase and during biofilm production. The kasA, kasB, and fas genes, which are involved in mycolic acid biosynthesis, were induced in biofilm cultures, as was dosR, therefore suggesting an inverse correlation in their expression compared with that of genes involved in c-di-GMP metabolism. The relative abundance within trehalose dimycolate (TDM) of α- mycolates decreased during biofilm maturation, with methoxy mycolates increasing over time, and keto species remaining practically stable. Moreover, addition of synthetic c-di-GMP to mid-log phase BCG cultures reduced methoxy mycolates, increased keto species and practically did not affect α-mycolates, showing a differential effect of c-di-GMP on keto- and methoxy-mycolic acid metabolism.
Andrea Navarro-Puyuelo,Inés Reyero,Ainara Moral,Fernando Bimbela,Miguel A. Bañares,Luis M. Gandía 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.80 No.-
Dry reforming and partial oxidation of biogas were studied using 0.5 wt.% Rh/Al2O3 catalysts, both inhouseprepared and commercial. The effects of O2 addition on syngas yield and biogas conversion werestudied at 700 C using different O2/CH4 ratios in the gas feeding stream: 0 (dry reforming), 0.12, 0.25,0.45 and 0.50. The highest CH4 conversion, H2 yield and H2/CO molar ratio were obtained with an O2/CH4ratio of 0.45, even though simultaneous valorization of both CH4 and CO2 could be best attained when theO2/CH4 ratio was 0.12. Increased biogas conversions and syngas yields were obtained by increasingreaction temperatures between 650 and 750 C. A detrimental influence on catalytic activity could beobserved when the catalyst was subjected to calcination. Increasing the hold time of the thermalconditioning of the catalyst under inertflow altered Rh dispersion, though had no significant impact oncatalyst performance in the dry reforming of methane at 700 C and 150 N L CH4/(gcat h). Characterizationof spent samples after reaction by Raman spectroscopy revealed the presence of carbonaceous deposits ofdifferent nature, especially on the commercial (named as Rh com) and calcined (Rh calc) catalysts, thoughoxygen addition in the biogas feed significantly reduced the amount of these deposits. The Rh catalyststhat had not been calcined after impregnation (Rh prep) did not present any noticeable characteristicpeaks in the G and D bands. In particular, scanning transmission electron microscopy (STEM) images ofthe spent Rh prep sample revealed the presence of very highly dispersed Rh nanoparticles after reaction,of particle sizes of about 1 nm, and no noticeable C deposits. Combined oxy-CO2 reforming of biogas usinghighly dispersed and low metal-loading Rh/Al2O3 catalysts with low O2 dosage in the reactor feed can beused to effectively transform biogas into syngas.