Supplementary Carbon Source Research Articles

Occurrence of Denitrifying Dephosphatation in a Hybrid Constructed Wetland System and Its Stability

This study was conducted to explore the startup characteristics and stability of a hybrid constructed wetland (HCW) system with a denitrifying dephosphatation process, which was composed of two tidal flow-constructed wetlands (termed T-A and T-B). As the system was operated according to the two-time feeding tidal flow operation mode, denitrifying dephosphatation and nitrification could be respectively enhanced in T-A and T-B, and the HCW achieved ideal simultaneous denitrification and phosphorus removal effects when treating domestic sewage. The introduction of periodical carbon source supplements for phosphorus harvesting alleviated excessive phosphorus accumulation in T-A and increased the storage of PHB within denitrifying phosphate-accumulating organisms (DPAOs). Subsequently, a stable and efficient denitrifying phosphorus removal effect could be guaranteed to some extent as the HCW system was operated during the test. As the phosphorus harvesting cycle length was 30 d, the mean phosphorus recovery efficiency of the HCW system was 63.97% throughout the experiment. Regarding the typical cycle, the mean TP and NOx--N removal efficiencies of T-A could respectively achieve (97.86±0.70)% and (98.29±2.62)% during the denitrifying dephosphatation process, and the amounts of phosphorus release and PHB synthesis in T-A could also reach up to (1486.29±123.25) mg and (4.43±0.57) mmol·g-1, respectively, during the phosphorus harvesting process. Meanwhile, the utilization rate of the supplementary carbon in the system was (94.65±2.66)%. To summarize, this study offers a new method for simultaneous denitrification and phosphorus removal in constructed wetlands, and expands the development and application range of phosphorus recovery processes.

Individual and combined supplementation of carbon sources for growth augmentation and enrichment of lipids in the green microalga Tetradesmus obliquus

Microalgae with high lipid productivity offer great promise as a potential source of biodiesel, an alternative to fossil diesel. Since a target of both high biomass yield and lipid content is difficult to attain with the classical photoautotrophic mode of nutrition, mixotrophy has evolved as a preferred mode for enhancement of growth in microalgae. In the present study, this strategy was explored extensively with six different exogenous carbon sources in eight different concentrations to investigate the effect of these carbon sources on the biomass and lipid production potential of the green alga Tetradesmus obliquus (SAG 276-3a). To further augment the effect of mixotrophy on the growth and lipid accumulation of the test microalga, selected carbon sources with their specific concentrations showing enhancement in both biomass yield and lipid accumulation in the first phase of the experiment were interacted with each other. Significant rise in biomass yield by twofold was seen in the case of 0.16% citrate + 0.08% bicarbonate interaction, whereas for lipid accumulation, maximum rise in lipid content (% dry cell wt.) by 2.3-fold and lipid yield (g L-1) by 4.5-fold was observed in the case of 0.16% acetate + 0.16% citrate-supplemented cultures. The biodiesel samples as analyzed using GC–MS were predominated with saturated and monounsaturated fatty acid methyl esters. Fuel property analysis of the biodiesel samples found them to be well suited to the Indian, American (ASTM), and European (EN) biodiesel standards.

Design and operation effect of corn starch wastewater treatment project

The corn starch wastewater was treated by the combination of “IC anaerobic + two-stage AO biochemical + modified Fenton”. The design parameters and treatment effects of the main construction sections of the project were introduced. The operation results of the project show that the combined process has a good treatment effect on corn starch wastewater. In the case where the average concentration of COD in the influent water is 17640 mg/L, the average concentration of NH3-N is 91.1 mg/L, and the average concentration of TN is 1266 mg/L. The average concentration of the COD, NH3-N and TN in the effluent water after treatment are 36mg/L, 1.2mg/L and 11.6mg/L, respectively, which meets the design standard requirements. The process control method of using some high-concentration organic wastewater beyond the anaerobic section can achieve the standard treatment of total nitrogen without the need of external supplementary carbon source, which has significant economic benefits.

Heterologous production of 3-hydroxyvalerate in engineered Escherichia coli

3-Hydroxyacids are a group of valuable fine chemicals with numerous applications, and 3-hydroxybutyrate (3-HB) represents the most common species with acetyl-CoA as a precursor. Due to the lack of propionyl-CoA in most, if not all, microorganisms, bio-based production of 3-hydroxyvalerate (3-HV), a longer-chain 3-hydroxyacid member with both acetyl-CoA and propionyl-CoA as two precursors, is often hindered by high costs associated with the supplementation of related carbon sources, such as propionate or valerate. Here, we report the derivation of engineered Escherichia coli strains for the production of 3-HV from unrelated cheap carbon sources, in particular glucose and glycerol. Activation of the sleeping beauty mutase (Sbm) pathway in E. coli enabled the intracellular formation of non-native propionyl-CoA. A selection of enzymes involved in 3-HV biosynthetic pathway from various microorganisms were explored for investigating their effects on 3-HV biosynthesis in E. coli. Glycerol outperformed glucose as the carbon source, and glycerol dissimilation for 3-HV biosynthesis was primarily mediated through the aerobic GlpK-GlpD route. To further enhance 3-HV production, we developed metabolic engineering strategies to redirect more dissimilated carbon flux from the tricarboxylic acid (TCA) cycle to the Sbm pathway, resulting in an enlarged intracellular pool of propionyl-CoA. Both the presence of succinate/succinyl-CoA and their interconversion step in the TCA cycle were identified to critically limit the carbon flux redirection into the Sbm pathway and, therefore, 3-HV biosynthesis. A selection of E. coli host TCA genes encoding enzymes near the succinate node were targeted for manipulation to evaluate the contribution of the three TCA routes (i.e. oxidative TCA cycle, reductive TCA branch, and glyoxylate shunt) to the redirected carbon flux into the Sbm pathway. Finally, the carbon flux redirection into the Sbm pathway was enhanced by simultaneously deregulating glyoxylate shunt and blocking the oxidative TCA cycle, significantly improving 3-HV biosynthesis. With the implementation of these biotechnological and bioprocessing strategies, our engineered E. coli strains can effectively produce 3-HV up to 3.71 g l−1 with a yield of 24.1% based on the consumed glycerol in shake-flask cultures.

Practicing anammox in a novel hybrid anaerobic-aerobic baffled reactor for treating high-strength ammonium piggery wastewater with low COD/TN ratio

A novel hybrid anaerobic-aerobic baffled reactor (HAOBR) with four compartments was constructed to treat manure-free piggery wastewater with an average COD/TN ratio as low as 0.98, without any supplement of external carbon source. Inoculated with aerobic activated sludge and operated at hydraulic retention time 36 h, 32 °C and reflux ratio 2.0, the reactor could perform steadily within 24 days. The removal of COD, NH4+-N and TN within the 21-days steady phase averaged 87.0%, 100% and 91.3%, respectively. Analysis of stoichiometry and results of high-throughput pyrosequencing revealed that the excellent nitrogen removal in the HAOBR was achieved by the cooperation of heterotrophic and autotrophic denitrification with anammox as the dominant approach. Compared with the previously developed microaerobic treatment processes and the recently reported modified A/O process, the HAOBR was more cost-efficient in treating manure-free piggery wastewater because of the less energy consumption, rapid startup process and efficient nutrients removal.

Effect of plant-based carbon source supplements on denitrification of synthetic wastewater: focus on the microbiology

The effects of plant-based carbon source addition on wastewater NO3--N removal and the involved microorganisms, especially denitrifying bacteria, were investigated. A synthetic wastewater (NO3--N, 15 mg/L) was treated through the batch experiment, which included three inoculation cycles (7 days/cycle), and was conducted at 25 °C. Four natural plant substrates, namely, rice straw (RS), wheat straw (WS), ryegrass (RG), and reed (RD), were used as carbon sources and supplemented at the rate of 1% (w/v). The results showed that both RS and WS performed well in promoting NO3--N removal (79.55-97.07%). While RG removed only 22.08% of NO3--N in the first cycle, the removal efficiency increased afterward (86.09-95.82%). Conversely, the NO3--N removal rate of RD decreased from 95.10 to 24.77% as a result of its low ability to supply carbon. With respect to the microorganisms, the RS treatment resulted in more bacteria and denitrifying genes such as narG, nirK, nirS, and norB than other treatments, while the highest number of nosZ gene copies was recorded in the WS treatment. Sequencing results revealed that Firmicutes (18.19-56.96%), Proteobacteria (38.82-74.80%), and Bacteroidetes (3.15-4.15%) were three dominant bacterial phyla for RS, WS, and RD treatments. Furthermore, the genera Enterobacter, Massilia, and Bacillus were the main denitrifying bacteria participating in the NO3--N removal. Furthermore, correlation analysis indicated that the denitrifying genus Sphingobacterium played an important role in enhancing nitrogen removal. This study suggested that RS is the superior plant-based carbon source for denitrifying bioreactors used in agricultural runoff treatment.

The Influences of Supplemental Vegetable Oils on the Growth and β-carotene Accumulation of Oleaginous Yeast-Rhodotorula glutinis

An oleaginous red yeast, Rhodotorula glutinis, synthesizes numerous compounds of industrial value, including those used as a source of microbial lipids for biodiesel applications. It can also be used to synthesize value-added products such as β-carotene, which are commonly used in several industries. Several vegetable oils are used in the medium as a supplemental carbon source for the enhancement of lipid and β-carotene accumulation. Among them, the supplemental of 25 g/L palm oil leads to the 71% increase of biomass as compared to that of the control batch in the agitation fermenter. The addition of palm oil not only improved the biomass yield but also enhanced the growth rate as well, where maximum growth rates of 0.32 and 0.27 g/L h were obtained with and without the addition of palm oil, respectively. The high biomass obtained will certainly lead to more total lipids and β-carotene accumulated. A comparison of an agitator bioreactor and an airlift bioreactor for biomass, total lipids, and β-carotene production was performed using palm oil as the supplemental carbon source. The shear force in the agitator bioreactor regulated the mixing of the palm oil in the medium, which increased the biomass production. The addition of palm oil slightly altered the fatty acid composition, which stearic acid (C18:0), oleic acid (C18:1) and linoleic acid (C18:2) were the predominant fatty acids in the microbial lipids of R. glutiniss. The results of this study suggest that an agitation bioreactor with palm oil supplementation increases biomass concentration and eventually increases β-carotene production.

Constructing a synthetic pathway for acetyl-coenzyme A from one-carbon through enzyme design

Acetyl-CoA is a fundamental metabolite for all life on Earth, and is also a key starting point for the biosynthesis of a variety of industrial chemicals and natural products. Here we design and construct a Synthetic Acetyl-CoA (SACA) pathway by repurposing glycolaldehyde synthase and acetyl-phosphate synthase. First, we design and engineer glycolaldehyde synthase to improve catalytic activity more than 70-fold, to condense two molecules of formaldehyde into one glycolaldehyde. Second, we repurpose a phosphoketolase to convert glycolaldehyde into acetyl-phosphate. We demonstrated the feasibility of the SACA pathway in vitro, achieving a carbon yield ~50%, and confirmed the SACA pathway by 13C-labeled metabolites. Finally, the SACA pathway was verified by cell growth using glycolaldehyde, formaldehyde and methanol as supplemental carbon source. The SACA pathway is proved to be the shortest, ATP-independent, carbon-conserving and oxygen-insensitive pathway for acetyl-CoA biosynthesis, opening possibilities for producing acetyl-CoA-derived chemicals from one-carbon resources in the future.

Liquid Waste Processing of Tofu Industry for Biomass Production as Raw Material Biodiesel Production

Indonesia as a producer of tofu generated more liquid waste. Nutrients that contained in the tofu wastewater are very useful for the production of microalgae. Chlorella sp. is a microalgae that potential for food supplement, pharmaceuticals, animal feed, aqua culture and cosmetics. Chlorella sp. comonly grow in sea water. Glycerol in the cultivation medium as supplemental organic carbon sources for Microalgae. Cultivation carried out for 9 days at different percentages volume of tofu liquid waste and addition of glycerol. The result showed that increased concentration of tofu waste in microalgae cultivation media is proportional to the increase in lipid levels of Chlorella sp. Variable of 70%V has the highest concentration of lipid. The addition of glycerol in the cultivation medium enchancing lipid production. Variable of 5 g/l glycerol has the highest concentration of lipid. The higher ratio of carbon and nitrogen produces higher lipid content.

From trash to treasure – turning plastic waste into biodegradable polymers using bacteria

Mountains of plastic waste consisting of carrier bags and medical packaging are buried in landfill sites dumped in rivers around the world annually. Unfortunately plastics generated by the petrochemical industry are not biodegradable and therefore accumulate in the environment at a rate of over 25 million tones year-1. Therefore there is a huge demand for biodegradable plastics. Polystyrene (PS), polyethylene (PE) and polypropylene (PP) are problematic materials, used for appliance housings, disposable cutlery and general packaging. This study investigates the utilisation of waste PS, PE and PP as a potential additional carbon sources using bacteria to synthesise polyhydroxyalkanoates (PHAs); a value-added material, able to replace some conventional fossil-fuel plastics while being non-toxic, fully biodegradable and biocompatible. Prodegraded waste PS and PP, and thermally treated PEwere used as supplementary carbon sources totryptone soya broth (TSB and BSM) for 48 h fermentations [1, 2, 3]. The bacterial strain Cupriavidus necator H16 was selected as it is non-pathogenic, genetically stable, robust and one of the best natural producers of PHA. The accumulation of PHAs varied from 17 % (wt / wt) of dry biomass in TSB controls to 39–66 % for PS, PE and PP thermally treated samples. The polymers obtained were analysed with nuclear magnetic resonance (NMR) and electrospray ionisation tandem mass spectrometry (ESI-MS/MS) to characterise their chemical structure. In conclusion, certain thermal treatment protocols of the waste plastics were shown to be viable for PHA production; with3-hydroxybutyrate and up to 12 mol% of 3-hydroxyvalerate and 3-hydroxyhexanoate co-monomeric units formed.

Nitrogen removal and responses of bacterial communities in activated sludge under different operational manipulations.

Operational conditions are often manipulated to improve the nitrogen removal performance of wastewater treatment, yet the impacts of operational conditions on microbial communities were still not well understood. There is a pressing need to understand the microbial mechanisms that link operation manipulation and nitrogen removal performance. In this study, high-throughput analysis of 16S rDNA and quantitative polymerase chain reaction of functional genes were used to identify the microbial response to operational manipulations. The results showed that alteration of operational parameters could change the bacterial communities at the genera level and denitrification guild gradually dominated in the activated sludge bacterial communities. Heterotrophic Hyphomicrobium and Chromatiaceae drove the kinetic of dominant genera and denitrification guild. Carbon source supplement was the most efficient strategy for improving nitrogen removal, and greatly increased the abundance of denitrifiers and denitrification genes. However, carbon source supplement inhibited expression activities of denitrification genes, as well as the proliferation of autotrophic denitrifiers, and it was supposed to be unfavorable in terms of cost over the long term. The result should bring new inspiration for improving the effect of WWTP performance through the manipulation of operational parameters.

Enhanced Growth of Pilin-Deficient Geobacter sulfurreducens Mutants in Carbon Poor and Electron Donor Limiting Conditions.

Geobacter sulfurreducens pili enable extracellular electron transfer and play a role in secretion of c-type cytochromes such as OmcZ. PilA-deficient mutants of G. sulfurreducens have previously been shown to accumulate cytochromes within their membranes. This cytochrome retaining phenotype allowed for enhanced growth of PilA-deficient mutants in electron donor and carbon-limited conditions where formate and fumarate are provided as the sole electron donor and acceptor with no supplementary carbon source. Conversely, wild-type G. sulfurreducens, which has normal secretion of cytochromes, has comparative limited growth in these conditions. This growth is further impeded for OmcZ-deficient and OmcS-deficient mutants. A PilB-deficient mutant which prevents pilin production but allows for secretion of OmcZ had moderate growth in these conditions, indicating a role for cytochrome localization to enabling survival in the electron donor and carbon-limited conditions. To determine which pathways enhanced growth using formate, Sequential Window Acquisition of all Theoretical Mass Spectra mass spectrometry (SWATH-MS) proteomics of formate adapted PilA-deficient mutants and acetate grown wild type was performed. PilA-deficient mutants had an overall decrease in tricarboxylic acid (TCA) cycle enzymes and significant upregulation of electron transport chain associated proteins including many c-type cytochromes and [NiFe]-hydrogenases. Whole genome sequencing of the mutants shows strong convergent evolution and emergence of genetic subpopulations during adaptation to growth on formate. The results described here suggest a role for membrane constrained c-type cytochromes to the enhancement of survival and growth in electron donor and carbon-limited conditions.

Tolerance of a sulfidogenic sludge to trichloroethylene at microcosms level as a basis for a long-term operation of reactors designed for its biodegradation

Trichloroethylene (TCE) is known as a toxic organic compound found as a pollutant in water streams around the world. The ultimate goal of the present work was to determine the TCE concentration that would be feasible to biodegrade on a long-term basis by a sulfidogenic sludge while maintaining sulfate reducing activity (SRA). Microcosms were prepared with sulfidogenic sludge obtained from a stabilized sulfidogenic UASB and amended with different TCE concentrations (100–300 µM) and two different proportions of volatile fatty acids (VFA) acetate, propionate and butyrate at COD of 2.5:1:1 and 1:1:1, respectively to evaluate the tolerance of the sludge. The overall results suggested that the continuous exposure of the microorganisms to TCE leads to inhibition of SRA; nonetheless, the SRA can be recovered after adequate supplementation of carbon sources and sulfate. The most suitable TCE concentration to operate on a long-term basis while preserving SRA was 26–35 mg L–1 (200–260 µM). A low level of expression of the mRNA of the sulfite reductase subunit alpha (dsrA) gene was obtained in the presence of the TCE and its intermediate products. This gene was associated to SRB belonging to the genera Desulfovibrio, Desulfosalsimonas, Desulfotomaculum, Desulfococcus, Desulfatiglans and Desulfomonas.

Investigation of lipid, carbohydrate and protein production from <i>Chlorella vulgaris</i> in controlled environment minkery wastewater

In an effort to incorporate a novel bioremediation technology into minkery wastewater treatment systems, this study aimed to investigate the effect of light cycles on the simultaneous production of Chlorella vulgaris biomass, lipid, carbohydrate, and protein in controlled environment minkery wastewater. Diluted minkery cage-washing wastewater used in the experiments, which were designed as a completely randomised design with a single factor (light cycle) experiment. The single factor had four levels: six-day continuous light (photoautotrophic), 48-h light/24-h dark (mixotrophic), 24-h light/48-h dark (mixotrophic), and six-day continuous dark (heterotrophic) cycle, which were randomly assigned to the 2.25-litre vertical column controlled environment photobioreactors (PBR), each equipped with an independent cool-white fluorescent light (8 W, 6,700 K) operated at room temperature. The pH in each PBR was monitored and controlled using independent pH meters and air pumps. During six-day cultivations, continuous light and 48-h light/24-h dark cycles achieved the largest biomass (82.50 mg L−1 day−1 and 79.50 mg L−1 day−1, respectively) and protein productivities (42.62 mg L−1 day−1 and 38.79 mg L−1 day−1, respectively) out of Chlorella vulgaris in minkery wastewater; however, using 48-h light/24-h dark cycle instead of continuous light cycle would reduce the energy cost of cultivation. The light cycles of continuous light, 48-h light/24-h dark, and 24-h light/48-h dark achieved the highest lipid (15.06 mg L−1 day−1, 16.03 mg L−1 day−1, 12.82 mg L−1 day−1, respectively) and carbohydrate (11.15 mg L−1 day−1, 11.89 mg L−1 day−1, 8.08 mg L−1 day−1, respectively) productivities, and there was no statistically significant difference in between; however, using 24-h light/48-h light cycle would again reduce the energy cost of cultivation compared to the other two cycles. Overall, for the cultivation of Chlorella vulgaris in minkery wastewater, the most appropriate light cycle for the production of microalgae biomass and crude protein seems to be the mixotrophic growth under 48-h light/24-h dark cycle, while the mixotrophic growth of 24-h light/48-h dark cycle was the most appropriate system for the production of lipid and carbohydrate. Providing a supplemental organic carbon source, preferably from another waste stream, has a potential to change the story with respect to the competitiveness of continuous dark (heterotrophic) cycle, and studying other microalgae strains may make minkery wastewater even more competitive compared to traditional culture mediums.

Investigation of lipid, carbohydrate and protein production from <i>Chlorella vulgaris</i> in controlled environment minkery wastewater

In an effort to incorporate a novel bioremediation technology into minkery wastewater treatment systems, this study aimed to investigate the effect of light cycles on the simultaneous production of Chlorella vulgaris biomass, lipid, carbohydrate, and protein in controlled environment minkery wastewater. Diluted minkery cage-washing wastewater used in the experiments, which were designed as a completely randomised design with a single factor (light cycle) experiment. The single factor had four levels: six-day continuous light (photoautotrophic), 48-h light/24-h dark (mixotrophic), 24-h light/48-h dark (mixotrophic), and six-day continuous dark (heterotrophic) cycle, which were randomly assigned to the 2.25-litre vertical column controlled environment photobioreactors (PBR), each equipped with an independent cool-white fluorescent light (8 W, 6,700 K) operated at room temperature. The pH in each PBR was monitored and controlled using independent pH meters and air pumps. During six-day cultivations, continuous light and 48-h light/24-h dark cycles achieved the largest biomass (82.50 mg L−1 day−1 and 79.50 mg L−1 day−1, respectively) and protein productivities (42.62 mg L−1 day−1 and 38.79 mg L−1 day−1, respectively) out of Chlorella vulgaris in minkery wastewater; however, using 48-h light/24-h dark cycle instead of continuous light cycle would reduce the energy cost of cultivation. The light cycles of continuous light, 48-h light/24-h dark, and 24-h light/48-h dark achieved the highest lipid (15.06 mg L−1 day−1, 16.03 mg L−1 day−1, 12.82 mg L−1 day−1, respectively) and carbohydrate (11.15 mg L−1 day−1, 11.89 mg L−1 day−1, 8.08 mg L−1 day−1, respectively) productivities, and there was no statistically significant difference in between; however, using 24-h light/48-h light cycle would again reduce the energy cost of cultivation compared to the other two cycles. Overall, for the cultivation of Chlorella vulgaris in minkery wastewater, the most appropriate light cycle for the production of microalgae biomass and crude protein seems to be the mixotrophic growth under 48-h light/24-h dark cycle, while the mixotrophic growth of 24-h light/48-h dark cycle was the most appropriate system for the production of lipid and carbohydrate. Providing a supplemental organic carbon source, preferably from another waste stream, has a potential to change the story with respect to the competitiveness of continuous dark (heterotrophic) cycle, and studying other microalgae strains may make minkery wastewater even more competitive compared to traditional culture mediums.

Characterisation of an Acrylamide-Degrading Bacterium and Its Degradation Pathway

Widespread use of acrylamide by the industry led to the environmental pollution that results from the indiscriminate discharge of acrylamide. The presence of acrylamide in the environment is a major threat due to its neurotoxic, carcinogenic and teratogenic properties. In this work bacterial isolate identified as Burkholderia sp. strain AQ5-13 is capable of degrading acrylamide as both its carbon and nitrogen sources were screen based on the capability of the bacteria to grow on solid basal salt media that contain 500 mg/L acrylamide as sole carbon and nitrogen sources without supplementation of additional carbon or nitrogen sources. Bacteria grow curve study was carried out by measuring the absorbance value at 600 nm. Burkholderia sp. strain AQ5-13 showed a complete life cycle in five days of incubation with no lag phase identified at the earlier growth phase. Optimum conditions for acrylamide degradation was conducted at different initial pH and incubation temperature. Growth optimisation of the bacteria was measured by plate counting in CFU after 48 h of incubation in 250 mL basal salt media that contain 500 mg/L acrylamide. Burkholderia sp. strain AQ5-13 showed optimum growth in acidic media at pH 5.7 (5.57 log 10 CFU/mL) and optimum growth at 30°C (6.84 log 10 CFU/mL) compared to other temperature ranges. Quantitative monitoring of acrylamide degradation was performed using HPLC. Burkholderia sp. strain AQ5-13 could degrade 14% of 500 mg/L acrylamide as its carbon and nitrogen sources after 72 h of incubation at 5 min of retention time. The appearance of acrylic acid peak as an intermediate was not detected, possibly because all the acrylic acid produced had been consumed immediately by the bacterium. The result from this study showed that bacteria Burkholderia sp. strain AQ5-13 has a good potential that can be applied in the bioremediation of waste containing acrylamide.

Fabrication of Self-Entangled 3D Carbon Nanotube Networks from Metal–Organic Frameworks for Li-Ion Batteries

Three-dimensional (3D) carbon nanomaterial assemblies are of great interest in emerging applications including electronic devices and energy storage because of their extraordinary high electrical conductivity and mechanical and thermal properties. However, the existing synthetic procedures of these materials are quite complex and energy-intensive. Herein, a facile approach is developed for fabricating a self-entangled carbon nanotube (CNT) network under convenient conditions (400 °C for 1 h), breaking the critical limitations of the current available methods. The keys of forming such 3D CNT network are the fragmentation of the sacrificial MOFs into nanosized particles, the reduction of metal elements in MOFs to highly active nanocatalysts by introducing hydrogen, and the supplement of external carbon source by introducing ethyne. In addition, the highly conductive 3D porous CNT network facilitates electron transfer and provides an excellent platform for high-performance Li-ion batteries (LIB).

Multi-Parameter Laser Imaging Reveals Complex Microscale Biofilm Matrix in a Thick (4,000 μm) Aerobic Methanol Oxidizing Community

Although methanol has frequently been used as an inexpensive supplementary carbon source to support treatment processes, knowledge of the resultant microbial biofilms, their 3D architecture, microenvironments, exopolymer chemistry and populations remains limited. We supplied methanol as a supplementary carbon source to biofilms developing in rotating annular reactors. Analysis of circulation waters (1.0 l d−1) indicated that dissolved organic carbon was reduced by 25%, NO3-nitrogen by 95%, and total phosphorus by 70%. Analyses of populations using culture based techniques and fluorescence in situ hybridization indicated enrichment of nitrifiers, denitrifiers, and methylotrophic bacteria relative to reference biofilms not receiving methanol. The biofilms that developed were up to 4,000 μm thick. Staining with fluor conjugated lectins in combination with nucleic acid stains, revealed the presence of discrete bacterial cells inside complex globular polymeric structures. These structures were in turn surrounded by an interstitial polymer containing a variety of bacterial cell types. The globular structures bound FITC-conjugated lectins, from Canavalia ensiformis and Ulex europeaus. The FITC-lectin of Phaseolus vulgaris bound the surface of the globular structures and more generally within the matrix. Chemical analyses of the polymer paralleled the results of lectin analyses indicating that the dominant neutral sugars were glucose, galactose, mannose, rhamnose, with fucose and ribose as minor constituents. Amino sugars were not detected. Dual channel imaging with pH sensitive probes indicated that pH gradients from pH 4 to 7 occurred across the globular microcolonies. Critically for the maintenance of aerobic conditions throughout the thick biofilm it was extensively penetrated by a fine fissure network revealed by the location of fluorescent latex microbeads as detected by confocal laser scanning microscopy. Microelectrode studies confirmed the absence of any detectable Eh gradients within the biofilm. However, mobility of various size-fractionated fluorescent probes indicated that the basal region was only penetrated by the lowest molecular weight probes with a hydrated radius of 2.2 nm or less. These observations indicate the selection of a unique, thick (>4,000 μm) microbial community in which a self-organized architecture promotes the maintenance of optimal conditions and metabolism throughout the biofilm community.

Nutrients removal performance and sludge properties using anaerobic fermentation slurry from food waste as an external carbon source for wastewater treatment

Enhancement of nitrogen and phosphate removal using thermophilic fermentation slurry from food waste (FSFW) as external carbon source was investigated. Based on the batch tests, the soluble and particulate fractions of the FSFW acted as easily and slowly biodegradable carbon sources, respectively, and the fermented slurry showed the combined nutrients removal properties of soluble and solid organics. During the long-term operation of a sequencing batch reactor (SBR) with FSFW for wastewater treatment, the sludge particle size increased obviously, the bacterial metabolic capacity improved significantly, and some functional microorganisms were enriched selectively, which significantly promoted the nitrogen removal efficiency (approximately 90%) by enhancing the anoxic denitrification and simultaneous nitrification and denitrification (SND) processes. Moreover, high phosphate removal efficiency (above 98%) was achieved through the aerobic and anoxic phosphate accumulation processes. Thus, using the FSFW as supplementary carbon source is a suitable solution for both food waste disposal and wastewater treatment.

Aerobic granular sludge and naphthenic acids treatment by varying initial concentrations and supplemental carbon concentrations.

Aerobic granular sludge (AGS) has previously been utilized in the treatment of toxic compounds due to its diverse and dense microbial structure. The present study subjected mature AGS to model naphthenic acids (NAs) representative of the Canadian oil sands. To this effect, three NA concentrations (10, 50 and 100 mg/L) and three supplemental carbon source concentrations (600, 1200 and 2500 mg/L) were studied in batch reactors for 5 days. The responding variables were chemical oxygen demand (COD), NA concentrations and nutrients. Cyclohexane carboxylic acid (CHCA), cyclohexane acetic acid (CHAA) and 1-adamantane carboxylic acid (ACA) were chosen to study structure-based degradation kinetics. The optimal COD according to the runs was 1200 mg/L. CHCA was removed completely with biodegradation rate constants increasing with lower NA concentrations and lower COD concentrations. CHAA was also removed completely, however, an optimal rate constant of 1.9 d-1 was achieved at NA and COD concentrations of 50 mg/L and 1200 mg/L, respectively. ACA removal trends did not follow statistically significant regressions; however, degradation and sorption helped remove ACA up to 19.9%. Pseudomonas, Acinetobacter, Hyphomonas and Brevundimonas spp. increased over time, indicating increased AGS adaptability to NAs.