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[en] Polyhydroxyalkanoates (PHAs) have been produced by various bacteria as natural polymers stored in bacterial cells as a source of carbon and energy. They are currently preferred biomaterials for use in many industrial fields instead of conventional non-degradable plastics. Due to their unique properties they can reduce pollution caused by the increasing global polymer demand. Pseudomonas species have been chosen as PHAs producers in many recent studies. Being metabolically versatile and possessing a remarkable tolerance to a wide range of carbon sources, these bacteria have become an efficient cell factory for PHAs production. Currently, attention is focused on the design of Pseudomonas strains to increase their ability to accumulate PHAs in the cell and modifying their biosynthetic pathways to obtain strains with modified compositions and improved properties. This article discusses the current state of knowledge of polyhydroxyalkanoates synthesized by Pseudomonas species which are industrially important microorganisms. This review provides an overview of recent trends towards PHA production, focusing on the utilization of low-cost carbon sources, fermentation strategies, PHAs properties and their uses as valuable bioproducts.
[en] Metal.containing carbon nanocomposites have shown significance promise in the area of energy storage, heterogeneous catalysis and material science because of their morphology and combined properties. Phosphorus.doped carbon nanocomposites with gold nanoparticles were developed by applying a simple impregnation method and metal deposition technique. Gold.phosphorus supported carbon nanocomposites with two sized (25 and 170 nm) were prepared from economical petroleum pitch residue as the carbon source using an advanced silica template method. These nanocomposites will lead to the novel applications in the field of material science with the combined properties of gold, phosphorus and carbon. The newly prepared gold phosphorus supported carbon nanocomposites were fully characterized using a range of different physico-chemical techniques
[en] Alpha-amylase was widely used in food industries, textile technology, paper manufacturing and so on. In this paper, the inducing mechanism of corn dextrins with different DE values (dextrose equivalent value) on production of a-amylase by Bacillus subtilis (B.subtilis) ZJF-1A5 was investigated. The results showed that the yield of a-amylase by B.subtilis ZJF-1A5 was increased by using dextrin with a certain DE value range as carbon source, which could be attributed to the presence of oligosaccharide in dextrins. By ordinary fermentation with oligosaccharide as carbon source, it was found that the inducing activity of maltopentaose was the strongest. It could be confirmed that the dextrins played important roles during the process of production of a-amylase by B.subtilis ZJF-1A5. (author)
[en] With a conjugative plasmid pJP4 carrying strain as the donor, two bioaugmentation experiments were conducted in a microcosm biofilm reactor with 2,4-D as the sole carbon source operated in fed-batch mode, and an enlarged lab-scale sequence batch biofilm reactor with mixed carbon sources of 2,4-D and other easily biodegradable compounds, respectively. In the microcosm study under sole carbon source condition, bioaugmentation led to a persistently increased 2,4-D degradation rate in the five operation cycles with enhancement of 13-64%. For the enlarged lab-scale bioaugmentation experiment under mixed carbon source conditions, no enhancement in 2,4-D removal could be observed during start-up period. After a period of operation, biofilm samples from the bioaugmented reactor demonstrated a stronger degradation capacity than the control and showed the presence of a large number of transconjugants. This study indicates that bioaugmentation based on plasmid horizontal transfer is a feasible strategy to establish functional microbial community in a biofilm reactor, and the strong selective pressure of 2,4-D existing alone and persistently was more favorable for the success of gene augmentation.
[en] Highlights: • Suspended and attached growth reactors were examined for Cr(VI) bio-reduction. • Molasses was proved an efficient and very low cost carbon source. • Molasses was more efficient than sugar in enhancing Cr(VI) reduction. • SBR with recirculation was the most proper operating mode. - Abstract: In the present study, indigenous microorganisms from industrial sludge were used to reduce the activity of Cr(VI). Molasses, a by-product of sugar processing, was selected as the carbon source (instead of sugar used in a previous work) as it is a low-cost energy source for bioprocesses. Initially, experiments were carried out in suspended growth batch reactors for Cr(VI) concentrations of 1.5–110 mg/L. The time required for complete Cr(VI) reduction increased with initial Cr(VI) concentration. Initial molasses concentration was also found to influence the Cr(VI) reduction rate. The optimal concentration for all initial Cr(VI) concentrations tested was 0.8 gC/L. Experiments were also carried out in packed-bed reactors. Three different operating modes were used to investigate the optimal performance and efficiency of the filter, i.e. batch, continuous and SBR with recirculation. The latter mode with a recirculation rate of 0.5 L/min lead to significantly high Cr(VI) reduction rates (up to 135 g/m2 d). The results of this work were compared with those of a similar work using sugar as the carbon source and indicate that molasses could prove a feasible technological solution to a serious environmental problem
[en] We report and solidly interpret the infrared spectrum of both pristine and oxidized carbynes embedded in a pure-carbon matrix. The spectra probe separately the effects of oxidation on sp- and on sp2-hybridized carbon, and provide information on the stability of the different structures in an oxidizing atmosphere. The final products are mostly short end-oxidized carbynes anchored with a double bond to sp2 fragments, plus an oxidized sp2 amorphous matrix. Our results have important implications for the realization of carbyne-based nano-electronics devices and highlight the active participation of carbynes in astrochemical reactions where they act as carbon source for the promotion of more complex organic species
[en] In order to get successful operation of advanced oxidative biological wastewater treatment system, adding of proper amount of carbon source which is an essential component for the microbial growth in the system is necessary. Sewage sludge is mainly composed by organic carbon. Many studies have focused on the recover of carbon source from waste sludge as well as reduction of sludge volume. Ozone, UV and chemical application have been adopted to recover the carbon source from waste sludge. Recently radiation process has been proposed to sludge reduction and disinfection owing to high energy power onto microbial disintegration. Radiation energy has shown us another potential possibility which is to get carbon source from the waste sludge. The aim of this study is to confirm that carbon source can be recovered from waste sludge by irradiation and how much percentage of nitrogen removal efficient can be improved in an advanced biological oxidative sewage treatment system(MLE)