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The thermotolerant yeast Kluyveromyces marxianus is a promising bioethanol producer, but its fermentation arrested earlier at high temperatures. Untargeted metabolomic analysis was used to explore K. marxianus’s stress responses during high-temperature fermentation. Fermentation experiments were conducted at 45 °C, with a group conducted at 30 °C as control. Samples were collected from both groups at 14 and 22 h and were subjected to metabolomic analysis. The results show that pathways related to biosynthesis of amino acids, metabolism of purine, pyridoxine and riboflavin, etc. were induced at high temperature. More oleic acid, less palmitic acid and less palmitoleic acid were synthesized at 45 °C than at 30 °C, indicating that K. marxianus can adapt to high temperature by increasing the mean fatty acid chain length. In addition, most of the metabolic pathways stopped after the fermentation arrest, but pathways related to amino acids metabolism, riboflavin metabolism, etc. were still active. This is the first study about comprehensive metabolomic profiling of K. marxianus during high-temperature fermentation. The findings in this study offer deeper insight in mechanisms of K. marxianus’s stress responses during high-temperature fermentation at the metabolome level, and provide potential target pathways for further metabolic engineering towards improved stress tolerance and efficient bioethanol production.

Bacteria have evolved several mechanisms to resist Cd toxicity, which are crucial for Cd detoxication and have the potential to be used for bioremediation of Cd. Geobacter species are widely found in anaerobic environments and play important roles in natural biogeochemical cycles. However, the transcriptomic response of Geobacter sulfurreducens under Cd stress have not been fully elucidated. Through integrated analysis of transcriptomic and protein-protein interaction (PPI) data, we uncovered a global view of mRNA changes in Cd-induced cellular processes in this study. We identified 182 differentially expressed genes (|log

A novel bioenergy-producing green alga (lab ID.: XNY8011) was isolated from a local mountain in Beijing, China, and was identified as a strain belonging to the genus of Coelastrum on the basis of morphological and molecular characterization. Physiological analyses of photobiological H 2 and lipid production suggested that XNY8011 could be a candidate for biofuels production. This strain could accumulate considerable biomass and produce massive chlorophylls in water diluted waste molasses. Three concentrations of molasses (0.1, 0.2 and 0.5%, w/v) were studied to optimize the cell growth and chlorophylls synthesis of XNY8011, and 0.2% was proved to be the optimum, in which XNY8011 could reach A600 of 1.55 ± 0.06 and produce 11.35 ± 0.93 μg/mL of chlorophylls. It was found that 25 °C is the most preferable temperature for the cell growth of XNY8011 in molasses. Interestingly, the strain XNY8011 exhibited significant low temperature adaptability when growing in waste molasses compared to typical bioenergy green algae. It produced 5.73 and 3.05 folds of cell densities in molasses than that Chlamydomonas reinhardtii CC503 and Chlorella vulgaris did under 20 °C, respectively, and even obtained 13.51 and 2.72 folds of cell densities under 15 °C, respectively. The dynamic analysis suggested that the sugar in waste molasses was utilized as carbon source for cell growth and biomass accumulation. The present study isolated a novel bioenergy-producing green alga from the native environment which could convert waste molasses to biomass and bioenergy with significant temperature adaptability.

High salinity organic wastewater (HSOW) contains both organic pollutants and high concentration of inorganic salts. If it is discharged into the environment without proper treatment, it will cause adverse consequences such as dehydration and death of aquatic organisms, and soil salinization. Bioelectrochemical systems (BESs) have been applied in various wastewater treatment processes. To assess the feasibility of using BESs to treat HSOW, the effect of applying potential on anaerobic digestion of HSOW was explored in an up-flow anaerobic sludge blanket (UASB) reactor poised at -0.6 V (vs. Ag/AgCl). When organic loading rate (OLR) was 2.16-2.88 kg chemical oxygen demand/(m

Bioethanol production based on solid-state fermentation (SSF) of sweet sorghum stalks has been demonstrated to have great potential due to the its low pollution and low cost. A novel S. cerevisiae strain TSH3 exhibited better SSF performance compared with BY4743 during SSF of sweet sorghum stalks. High-quality total RNA of S. cerevisiae was extracted from SSF mixture and the global gene expression profiles during SSF were studied using RNA-Seq. Compared with BY4743, TSH3’s genes related to ribosome biogenesis, amino acid and coenzyme metabolism during early fermentation stage, secondary metabolite biosynthesis, metabolism in diverse environment during middle fermentation stage, and lipid metabolism during late fermentation stage were up-regulated; while the genes involved in fatty acid metabolism and peroxisome during early fermentation stage, ribosome biogenesis during middle fermentation stage, and mitotic cell cycle during late fermentation stage were down-regulated. Further dynamic analysis of TSH3’s transcriptome reveals its three different metabolic stages: 1) ribosome biogenesis and respiration-fermentation transition; 2) biosynthesis of secondary metabolites and stress resistance; 3) plasma membrane related metabolism for stress resistance. These findings provided insight into the S. cerevisiae transcriptome during SSF of sweet sorghum stalks and suggest that TSH3 would be an ideal candidate for SSF-based bioethanol production.

In this article, we review the advancement in nanoseparation and concomitant purification of nanoparticles (NPs) by using density gradient ultracentrifugation technique (DGUC) and demonstrated by taking several typical examples. Study emphasizes the conceptual advances in classification, mechanism of DGUC and synthesis-structure-property relationships of NPs to provide the significant clue for the further synthesis optimization. Separation, concentration, and purification of NPs by DGUC can be achieved at the same time by introducing the water/oil interfaces into the separation chamber. We can develop an efficient method “lab in a tube” by introducing a reaction zone or an assembly zone in the gradient to find the surface reaction and assembly mechanism of NPs since the reaction time can be precisely controlled and the chemical environment change can be extremely fast. Finally, to achieve the best separation parameters for the colloidal systems, we gave the mathematical descriptions and computational optimized models as a new direction for making practicable and predictable DGUC separation method. Thus, it can be helpful for an efficient separation as well as for the synthesis optimization, assembly and surface reactions as a potential cornerstone for the future development in the nanotechnology and this review can be served as a plethora of advanced notes on the DGUC separation method.

Biogas produced from anaerobic digestion usually contains 30%-50% CO2, much of which must be removed, before utilization. Bioelectrochemical biogas upgrading approaches show promise, however, they have not yet been optimized for practical applications. In this study, a bioelectrochemical system with low energy input (applied cathode potential of -0.5 V vs. standard hydrogen electrode, SHE) was used for in-situ biogas upgrading. High efficiency CO2 conversion (318.5 mol/d/m2) was achieved when the system was operated with an organic load of 1.7 kgCOD/(m3 d). Methane content in the upgraded biogas was 97.0% and CO2 concentrations stayed below 3%, which is comparable to biogas upgraded with more expensive and less sustainable physiochemical approaches. The high efficiency of this approach could likely be attributed to a significant enrichment of Methanothrix (92.7%) species on the cathode surface that were expressing genes involved in both acetogenic methanogenesis and direct electron transfer (DET). Electromethanogenesis by these organisms also increased proton consumption and created a higher pH that increased the solubility of CO2 in the bioreactor. In addition, CO2 removal from the biogas was likely further enhanced by an enrichment of Actinobacillus species known to be capable of CO2 fixation. Artificial neural network (ANN) models were also used to estimate CH4 production under different loading conditions. The ANN architecture with 10 neurons at hidden layers fit best with a mean square error of 6.06 × 10−3 and R2 of 0.99.

In this study, an Escherichia coli (E. coli) whole-cell biosensor for the specific detection of bioavailable arsenic was developed by placing a green fluorescent protein (GFP) reporter gene under the control of the ArsR1 (GSU2952) regulatory circuit from Geobacter sulfurreducens. E. coli cells only emitted green fluorescence in the presence of arsenite and were more sensitive to arsenite when they were grown in M9 supplemented medium compared to LB medium. Under optimal test conditions, the Geobacter arsR1 promoter had a detection limit of 0.01 μM arsenite and the GFP expression was linear within a range of 0.03–0.1 μM (2.25–7.5 μg/l). These values were well below World Health Organization’s drinking water quality standard, which is 10 μg/l. The feasibility of using this whole-cell biosensor to detect arsenic in water samples, such as arsenic polluted tap water and landfill leachate was verified. The biosensor was determined to be just as sensitive as atomic fluorescence spectrometry. This study examines the potential applications of biosensors constructed with Geobacter ArsR-Pars regulatory circuits and provides a rapid and cost-effective tool that can be used for arsenic detection in water samples.

Developing low-cost yet highly efficient earth-abundant electrocatalysts for oxygen evolution reaction (OER) is of great significance for industrial scale water splitting for clean hydrogen production, as well as for rechargeable metal-air batteries. In searching for advanced catalysts, it is equally important to fundamentally understand working mechanism and be able to rationally design and manipulate catalytic sites. Starting from the density functional theory (DFT) calculations as a guidance, our theoretical model revealed that chromium substitution in nickel–iron hydroxides (Ni1-xFex(OH)2) not only accelerated the charge transfer but also regulated the adsorption energy of OER intermediates to achieve optimal binding strength. Experimentally, chromium was doped into the laminate of Ni1-xFex(OH)2, resulting in the enhanced catalytic performance for oxygen evolution reaction, which confirmed the predictions from the theoretical data. The porous and ultra-thin ternary Ni1-x-yFexCry(OH)2 electrocatalysts were grown directly on a nickel foam (NF) substrate, with an optimum composition Ni0.66Fe0.27Cr0.07(OH)2/NF identified, which exhibited a superior OER performance, i.e., achieving a significant current density of 10 mA cm−2 at a low overpotential of 231 mV, a small Tafel slope (31 mV dec−1) and an excellent stability at a highly oxidative potential of 1.68 V vs RHE in alkaline electrolyte. The comprehensive study involving both theoretical and experimental results in this work provides an insightful guidance in designing efficient OER catalysts for chemical and electrical energy conversion and storage.

The aqueous Nickel–Zinc batteries have advantages of high safety and environmental benignity. However, their low energy density and poor cycling stability hinder their widespread applications. To address these issues, we demonstrate here a well-aligned hierarchical nanowires array as an advanced cathode for Nickel–Zinc batteries, which is composed of Nickel-vanadium layered double hydroxide decorated on cobalt oxide with a core/sheath configuration featuring merits of high electrical conductivity, large specific surface area, and short diffusion pathway for ions and electrons. Benefiting from the hierarchy structure design and component synergistic effect, the nanowires array electrode with high mass-loading of 11.1 mg cm −2 exhibits high areal capacity of 1.98 mAh cm −2 at 5 mA cm −2 , 61.8% capacity retention at 50 mA cm −2 and excellent cycling stability with 100% retention after 1000 cycles. Moreover, full cell of the as-fabricated nanowiress arrays//Zinc configuration delivers high operating voltage of 1.71 V, energy density up to 2.2 mWh cm −2 , power density up to 82.0 mW cm −2 and remarkable cycling stability of 89% capacity retention after 1500 cycles, showing great potential for practical applications. This work may also bring new design opportunities for the well-defined nanoarrays electrode in other energy storage devices.