2-Butanol and Butanone Production in Saccharomyces cerevisiae through Combination of a B-12 Dependent Dehydratase and a Secondary Alcohol Dehydrogenase Using a TEV-Based Expression System

2-Butanol and its chemical precursor butanone (methyl ethyl ketone -MEK) are chemicals with potential uses as biofuels and biocommodity chemicals. In order to produce 2-butanol, we have demonstrated the utility of using a TEV-protease based expression system to achieve equimolar expression of the individual subunits of the two protein complexes involved in the B-12-dependent dehydratase step (from the pdu-operon of Lactobacillus reuterii), which catalyze the conversion of meso-2,3-butanediol to butanone. We have furthermore identified a NADH dependent secondary alcohol dehydrogenase (Sadh from Gordonia sp.) able to catalyze the subsequent conversion of butanone to 2-butanol. A final concentration of 4 +/- 0.2 mg/L 2-butanol and 2 +/- 0.1 mg/L of butanone was found. A key factor for the production of 2-butanol was the availability of NADH, which was achieved by growing cells lacking the GPD1 and GPD2 isogenes under anaerobic conditions

Hybrid chitosan derivative-carbon suport for oxygen reduction reactions

New hybrid chitosan derivative-carbon black was prepared and used as support for Pt nanoparticles. These catalysts improved the activity toward oxygen reduction reaction (ORR), compared with those of commercial Pt/C catalyst. The biopolymer chitosan provided an efficient and sustainable surface nitrogen source associated with the superior performance of the catalysts.Peer reviewe

Production of 2-butanol through meso-2,3-butanediol consumption in lactic acid bacteria

2-Butanol has been an issue of industries in many areas, for example, biofuel production (as an advanced alternate fuel), fermented beverages, and food (as taste-altering component). Thus, its source of production, the biological pathway, and the enzymes involved are of high interest. In this study, 42 different isolates of lactic acid bacteria from nine different species were screened for their capability to consume meso-2,3-butanediol and produce 2-butanol. Lactobacillus brevis was the only species that showed any production of 2-butanol. Five of ten tested isolates of L.brevis were able to convert meso-2,3-butanediol to 2-butanol in a synthetic medium (SM2). However, none of them showed the same capability in a complex medium such as MRS indicating that the ability to produce 2-butanol is subject to some kind of repression mechanism. Furthermore, by evaluating the performance of the enzymes required to convert meso-2,3-butanediol to 2-butanol, that is, the secondary alcohol dehydrogenase and the diol dehydratase, it was shown that the latter needed the presence of a substrate to be expressed

Novel methods for the synthesis of 3-arylmethyl-4-thiazolidine carboxylic acid-2-thiones and their methyl esters

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Chromium removal from aqueous solution by a PEI-silica nanocomposite

It is essential and important to determine the adsorption mechanism as well as removal efficiency when using an adsorption technique to remove toxic heavy metals from wastewater. In this research, the removal efficiency and mechanism of chromium removal by a silica-based nanoparticle were investigated. A PEI-silica nanoparticle was synthesized by a one-pot technique and exhibited uniformly well-dispersed PEI polymers in silica particles. The adsorption capacity of chromium ions was determined by a batch adsorption test, with the PEI-silica nanoparticle having a value of 183.7 mg/g and monolayer sorption. Adsorption of chromium ions was affected by the solution pH and altered the nanoparticle surface chemically. First principles calculations of the adsorption energies for the relevant adsorption configurations and XPS peaks of Cr and N showed that Cr(VI), [HCrO4](-) is reduced to two species, Cr(III), CrOH2+ and Cr3+, by an amine group and that Cr(III) and Cr(VI) ions are adsorbed on different functional groups, oxidized N and NH3+

Barriers to blockchain adoption in humanitarian logistics in an uncertain environment

In the digital age, blockchain technology is recognized as an operational innovation that is rapidly joining the field of supply chain and humanitarian logistics. Hence, blockchain technology has the potential to fundamentally change the field of humanitarian aid, but still relatively little research has been published aimed at improving understanding of the various barriers to blockchain adoption in humanitarian logistics. The aim of this research is to provide an integrated framework for evaluating the barriers to blockchain adoption in the field of humanitarian logistics. To assess the barriers, integrated approach has been applied in three phases. In the first phase of this approach, based on the literature, 10 barriers to the adoption of blockchain in humanitarian logistics are identified and evaluated using the FMEA method. In the second phase, using the opinions of experts, the weights of the three factors are calculated. Then, in the third phase and according to the outputs of the previous phases, obstacles are prioritized using the proposed Z-ARAS method. In addition to assigning different weights to the three factors considering uncertainty and reliability in barriers is also considered in this approach through the theory of Z numbers. The proposed approach of current study was implemented in the evaluation of blockchain adoption barriers in humanitarian logistics. According to the results, the most critical barriers concern with integrating issues, risk of cyber-attacks, and technology risks. The results shown the capability and superiority of the proposed approach compared to other traditional methods such as FMEA and Fuzzy ARAS

Selective Liquid Phase Oxidation of Ethyl Benzene to Acetophenone by Palladium Nanoparticles Immobilized on g-C3N4-rGO Composite as Recyclable Catalyst

peer reviewe

Copper nanoparticles embedded into nitrogen-doped carbon fiber felt as recyclable catalyst for benzene oxidation under mild conditions

peer reviewedHerein, an active and stable nanocatalyst based on copper nanoparticles embedded into nitrogen-doped carbon fiber felts (N[sbnd]CFFs) was fabricated through a co-assembly protocol. The catalytic performance of Cu (20 wt.%)/N[sbnd]CFF was contributed to its structural and morphological features, which were studied by various characterization techniques. The data illustrated that the catalyst showed reasonable activity and excellent selectivity in oxidation of benzene-to-phenol (25.2 and 100% for yield and selectivity respectively) in the presence of an environmentally-friendly oxidant. Furthermore, the microscopic catalyst kept its long-term performance until nine successive runs, which turns it into a bulk alternative in large-scale schemes

Genetically controlled mtDNA deletions prevent ROS damage by arresting oxidative phosphorylation

Deletion of mitochondrial DNA in eukaryotes is currently attributed to rare accidental events associated with mitochondrial replication or repair of double-strand breaks. We report the discovery that yeast cells arrest harmful intramitochondrial superoxide production by shutting down respiration through genetically controlled deletion of mitochondrial oxidative phosphorylation genes. We show that this process critically involves the antioxidant enzyme superoxide dismutase 2 and two-way mitochondrial-nuclear communication through Rtg2 and Rtg3. While mitochondrial DNA homeostasis is rapidly restored after cessation of a short-term superoxide stress, long-term stress causes maladaptive persistence of the deletion process, leading to complete annihilation of the cellular pool of intact mitochondrial genomes and irrevocable loss of respiratory ability. This shows that oxidative stress-induced mitochondrial impairment may be under strict regulatory control. If the results extend to human cells, the results may prove to be of etiological as well as therapeutic importance with regard to age-related mitochondrial impairment and disease