The butyrogenic genes from Clostridium difficile DSM 1296 T have been cloned and expressed in Escherichia coli. The enzymes acetyl-coenzyme A (CoA) C-acetyltransferase, 3-hydroxybutyryl-CoA dehydrogenase, crotonase, phosphate butyryltransferase, and butyrate kinase and the butyryl-CoA dehydrogenase complex composed of the dehydrogenase and two electron-transferring flavoprotein subunits were individually produced in E. coli and kinetically characterized in vitro. While most of these enzymes were measured using well-established test systems, novel methods to determine butyrate kinase and butyryl-CoA dehydrogenase activities with respect to physiological function were developed. Subsequently, the individual genes were combined to form a single plasmid-encoded operon in a plasmid vector, which was successfully used to confer butyrate-forming capability to the host. In vitro and in vivo studies demonstrated that C. difficile possesses a bifurcating butyryl-CoA dehydrogenase which catalyzes the NADH-dependent reduction of ferredoxin coupled to the reduction of crotonyl-CoA also by NADH. Since the reoxidation of ferredoxin by a membrane-bound ferredoxin:NAD ؉ -oxidoreductase enables electron transport phosphorylation, additional ATP is formed. The butyryl-CoA dehydrogenase from C. difficile is oxygen stable and apparently uses oxygen as a cooxidant of NADH in the presence of air. These properties suggest that this enzyme complex might be well suited to provide butyryl-CoA for solventogenesis in recombinant strains. The central role of bifurcating butyryl-CoA dehydrogenases and membrane-bound ferredoxin:NAD oxidoreductases (Rhodobacter nitrogen fixation [RNF]), which affect the energy yield of butyrate fermentation in the clostridial metabolism, is discussed. G enome sequencing of organisms provides information regarding the distribution of genes encoding biotechnologically important metabolic pathways. This is true for the clostridial butyrogenic pathway, which converts acetyl-conenzyme A (CoA)-the terminal oxidation product of glucose via glycolysis-to butyrate. Genes encoding enzymes from this pathway are widespread in genome-sequenced clostridia and related species (1-8). In spite of the central importance of butyrate-forming genes in these organisms, only individual enzymes from a comparably small selection of organisms have been purified and carefully studied in the past (9-15). In particular, Clostridium acetobutylicum enzymes were of great interest due to the organism's capability of producing acetone and butanol (16)(17)(18). Driven by the urgent need to replace oil-derived fossil fuels, genetic engineering of microbes for production of butan-1-ol, a promising alternative transportation fuel, is proceeding worldwide (16,(18)(19)(20)(21)(22)(23)(24).A long-known metabolic route such as the butyrate pathway (Fig. 1A) can suddenly gain fundamentally new meanings when hitherto-unknown properties of individual enzymes within this pathway become known. While for decades the role of butyrate formation was generally a...
Ginger and garlic plants were used for the preparation of water and ethanolic extracts. The silver, copper, iron and zinc nanoparticles were eco-friendly synthesized using ginger and garlic extracts and their antioxidant and antibacterial activities were evaluated. The growth of nanoparticles was complemented with characterization using TEM and UV-Vis spectroscopic analysis. Transmission electron microscopy revealed the presence of mono-dispersed metals nanoparticles and silver nanoparticles of ginger have the smallest particle size around 10.10-18.33 nm. The investigated samples were evaluated as antibacterial agents against Staphylococcus aureus, Klebsiella pneumoniae, Candida albicans, Bacillus subtilis, Erwinia carotovora and Proteus vulgaris and as antifungal agents against C. albicans. The results of antimicrobial tests indicate that these nanoparticles possess significant activities compared to the results obtained by antibiotic standard. In addition, the total polyphenols, fractionation of phenols, flavonoids by high-performance liquid chromatography systems and antioxidant activity were evaluated. Graphical AbstractComparison of the DPPH and ABTS antioxidant results.
In recent years, cereals especially barley and oat grains have attracted researches and commercial attention mainly due to their high contents of dietary fibers, βglucan and phenolic compounds with high antioxidant activates. Therefore, a preliminary study was carried out to estimate the components of raw barley and oat grains as well as, the effect of germination process on chemical composition and biological active compounds. The obtained results reveled that the germination process had a great role on the efficiency of chemical composition of selected cereal grains. A large number of negatively valued components in the grains such as crude fibers and starch contents of barley and oat decreased with prolonging the germination time process and the reduction of their contents due to the activity of αamylase enzymes during germination process which led to an increase in total sugars. Phytic acid decline with germination time increase. Otherwise, protein contents gradually increased with prolonging the germination period being 15.24 and 12.96% after three days for barley and four days for oat, respectively. Prolonging the germination time increased the minerals content of barley and oat grains and improved the bioavailability of essential minerals. Moreover, β-glucan contents declined with increasing the germination time process. Prolonging germination period increased total phenolic compounds, flavonoids contents and antioxidant activity, Catechin and pyrogallol were the major free phenolic compounds that existed in raw and germinated barley and oat grains. Nicotinic acid and Vit. B1 were the most abundant B complex vitamins in raw barley and oat grains and they highly increased during the germination period more than two folds recording 120.81 and 145.56 mg/100g & 335.21 and 441.62 mg/100g, respectively. Finally, it could be concluded that germination process had positive effects to improve the bioactive compounds contents as total phenolic and flavonoids compounds, antioxidant activity and an increase in bioavailability of essential minerals and a higher content of Vit. B complex of barley and oat grains.
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