Potential Carbon Source Research Articles

Converting perennial ryegrass into lipid using the oleaginous yeast Metschnikowia pulcherrima

Grass, a low-cost lignocellulosic feedstock with relatively low lignin content, serves as a potential carbon source for microbial processes due to its polymeric sugar content. However, converting carbohydrates into monomeric sugars presents challenges due to complex lignocellulosic matrix. In this study, a mixture of perennial ryegrass and white clover (RG) was pretreated with alkaline before being enzymatically hydrolysed for use as a fermentable sugar source for the oleaginous yeast Metschnikowia pulcherrima. The dilute alkaline pretreatment approach resulted in a 3 times improvement in the conversion of RG, yielding a fermentable sugar concentration of 56.5 g/L. The yeast exhibited a growth yield (Ym/m) of 0.47, producing 23.7 g/L of dry cell weight at 20°C over 140 hours, with a lipid content of 37 % with a similar composition to high oleic palm oil. These findings suggest that RG can be utilised for formulating an oleaginous yeast medium containing the necessary nutrients.

Generation of a Vibrio-based platform for efficient conversion of raffinose through Adaptive Laboratory Evolution on a solid medium.

Raffinose, a trisaccharide abundantly found in soybeans, is a potential alternative carbon source for biorefineries. Nevertheless, residual intermediate di- or monosaccharides and low catabolic efficiency limit raffinose use through conventional microbial hosts. This study presents a Vibrio-based platform to convert raffinose efficiently. Vibrio sp. dhg was selected as the starting strain for the Adaptive Laboratory Evolution (ALE) strategy to leverage its significantly higher metabolic efficiency. We conducted ALE on a solid minimal medium supplemented with raffinose to prevent the enrichment of undesired phenotypes due to the shared effect of extracellular raffinose hydrolysis among multiple strains. As a result, we generated the VRA10 strain that efficiently utilizes raffinose without leaving behind degraded di- or monosaccharides, achieving a notable growth rate (0.40 h-1) and raffinose consumption rate (1.2g/gdcw/h). Whole genome sequencing and reverse engineering identified that a missense mutation in the melB gene (encoding a melibiose/raffinose:sodium symporter) and the deletion of the two galR genes (encoding transcriptional repressors for galactose catabolism) facilitated rapid raffinose utilization. The further engineered strain produced 6.2g/L of citramalate from 20g/L of raffinose. This study will pave the way for the efficient utilization of diverse raffinose-rich byproducts and the expansion of alternative carbon streams in biorefinery applications.

Dried Anaerobic Digestate from Slaughterhouse By-products: Emerging Cues for a Bio-Based Fertilization

AbstractThe slaughterhouse and meat industry are worldwide rapidly growing and produce billions of tonnes of organic wastes annually. These materials can be used to produce biogas through anaerobic digestion and the resulting digestate represents a potential source of organic carbon and nutrients that could be applied to the soil as organic fertilizer. The present work aims to assess the fertilizing potential of a dried anaerobic digestate (DD) produced from beef slaughtering waste. DD was characterized at the physic-chemical level, particularly focusing on macro- and micronutrient contents, potentially toxic element and organic contaminants. Then, a short-term soil incubation experiment was performed on two different soils. After the incubation, DD released 10–26% of their total nitrogen (N) and 13–16% of total phosphorus (P), depending on the soils that had different characteristics and responded differently to the treatments. However, DD had positive effects on the principal soil fertility indicators, such as chitinase and phosphatases, stimulating the microbial activity and therefore exploiting a fertilizing potential as well as the other organic fertilizers tested. Moreover, DD had minor effects on soil extractable carbon (Cext) suggesting the presence of recalcitrant C forms in spite of soluble C, indicating a higher stability of slaughterhouse by-products after anaerobic digestion in respect to the other organic fertilizers. The results obtained in this work raise the concrete possibility use DD as a bio-based fertilizer. Graphical Abstract

Molecular evidence of internal carbon-driven partial denitrification in a mainstream pilot A-B system coupled with side-stream EBPR treating municipal wastewater

Achieving mainstream short-cut nitrogen removal via nitrite has become a carbon and energy efficient way, but still remains challenging for low-strength municipal wastewaters. This study integrated sidestream enhanced biological phosphorus removal system in a pilot-scale adsorption/bio-oxidation (A-B) process (named A-B-S2EBPR system) and nitrite accumulation was successfully achieved for treating the municipal wastewater. Nitrite could accumulate to 5.5 ± 0.3 mg N/L in the intermittently aerated tanks of B-stage with the nitrite accumulation ratio (NAR) of 79.1 ± 6.5 %. The final effluent concentration and removal efficiency of total inorganic nitrogen (TIN) were 4.6 ± 1.8 mg N/L and 84.9 ± 5.6 %, respectively. In-situ process performance of nitrogen conversions, routine batch nitrification/denitrification activity tests and functional gene abundance of nitrifiers collectively suggested that the nitrite accumulation was mainly caused by partial denitrification rather than out-selection of nitrite oxidizing bacteria (NOB). Moreover, the single-cell Raman spectroscopy analysis first demonstrated that there was a specific microbial population that could utilize polyhydroxyalkanoates (PHA) as the potential internal carbon source during the partial denitrification process. The integration of S2EBPR brings unique features to the conventional A-B process, such as extended anaerobic retention time, lower oxidation–reduction potential (ORP), much higher and complex volatile fatty acids (VFAs) etc., which can largely reshape the microbial communities. The dominant genera were Acinetobacter and Comamonadaceae, which accounted for (17.8 ± 15.5)% and (6.7 ± 3.4)%, respectively, while the relative abundance of conventional nitrifiers was less than 0.2%. This study provides insights into phylogenetic and phenotypic shifts of microbial communities when incorporating S2EBPR into the sustainable A-B process to achieve mainstream short-cut nitrogen removal.

Effects of bagasse as a carbon source on biofloc formation, water quality, and microbial community structure in shrimp culture system.

As a widely available, low-cost agricultural byproduct, bagasse is a potential solid carbon source and provides microbial attachment as a biofilm carrier. In this study, the effects of bagasse as a carbon source on biofloc formation, water quality, microbial community structure, and nitrogen conversion in a shrimp culture system were explored, and the performance of bagasse bioflocs was assessed. No bagasse was added to the control group (CK), and three bagasse addition groups were set up, with the floc content of the water maintained at 5 mL/L (BF5 group), 10 mL/L (BF10 group), and 15 mL/L (BF15 group). The results showed that bagasse bioflocs formed in the fourth week when bagasse was placed in the culture water, and the surface of bagasse was covered with thick biofilm at that time. The DOC content of the BF15 group was significantly greater than that of the CK group, from 30.31 to 105.06% (P < 0.05), and the DOC increased with increasing bagasse biofloc content. The BF group rapidly converted TAN to NO2--N and then to NO3--N because the accumulation of nitrite nitrogen in the BF15 group occurred 1 week earlier than in the other groups; at the 8th week, the nitrite nitrogen conversion rate of each BF group was close to 100%, which was significantly greater than that of the CK group (P < 0.05). The relative abundances of genes encoding microbial glutamate dehydrogenase and glutamate synthase increased in the bagasse biofloc groups (P < 0.05). The relative abundances of genes from Rhodobacterales and Hyphomicrobiales in each group were greater, but bagasse bioflocs increased the proportion of Hyphomicrobiale. In summary, adding bagasse to the shrimp culture system can form a biofloc system, resulting in the formation of a rich bacterial biofilm on its surface. Bagasse addition not only affects the composition of microbial communities but also accelerates the nitrification process in water. As a result, ammonia and nitrite are converted into nitrate, which is essential for maintaining the stability of the ecosystem balance in aquaculture water.

Structural insights in to the atypical type-I ABC Glucose-6-phosphate importer VCA0625-27 of Vibrio cholerae

Sugar phosphates are potential sources of carbon and phosphate for bacteria. Despite that the process of internalization of Glucose-6-Phosphate (G6P) through plasma membrane remained elusive in several bacteria. VCA0625-27, made of periplasmic ligand binding protein (PLBP) VCA0625, an atypical monomeric permease VCA0626, and a cytosolic ATPase VCA0627, recently emerged as hexose-6-phosphate uptake system of Vibrio cholerae. Here we report high resolution crystal structure of VCA0625 in G6P bound state that largely resembles AfuA of Actinobacillus pleuropneumoniae. MD simulations on VCA0625 in apo and G6P bound states unraveled an ‘open to close’ and swinging bi-lobal motions, which are diminished upon G6P binding. Mutagenesis followed by biochemical assays on VCA0625 underscored that R34 works as gateway to bind G6P. Although VCA0627 binds ATP, it is ATPase deficient in the absence of VCA0625 and VCA0626, which is a signature phenomenon of type-I ABC importer. Further, modeling, docking and systematic sequence analysis allowed us to envisage the existence of similar atypical type-I G6P importer with fused monomeric permease in 27 other gram-negative bacteria.

Biodegradation of polyethylene by the marine fungus Parengyodontium album

Plastic pollution in the marine realm is a severe environmental problem. Nevertheless, plastic may also serve as a potential carbon and energy source for microbes, yet the contribution of marine microbes, especially marine fungi to plastic degradation is not well constrained. We isolated the fungus Parengyodontium album from floating plastic debris in the North Pacific Subtropical Gyre and measured fungal-mediated mineralization rates (conversion to CO2) of polyethylene (PE) by applying stable isotope probing assays with 13C-PE over 9 days of incubation. When the PE was pretreated with UV light, the biodegradation rate of the initially added PE was 0.044 %/day. Furthermore, we traced the incorporation of PE-derived 13C carbon into P. album biomass using nanoSIMS and fatty acid analysis. Despite the high mineralization rate of the UV-treated 13C-PE, incorporation of PE-derived 13C into fungal cells was minor, and 13C incorporation was not detectable for the non-treated PE. Together, our results reveal the potential of P. album to degrade PE in the marine environment and to mineralize it to CO2. However, the initial photodegradation of PE is crucial for P. album to metabolize the PE-derived carbon.

Advances in the Production of Sustainable Bacterial Nanocellulose from Banana Leaves.

Interest in bacterial nanocellulose (BNC) has grown due to its purity, mechanical properties, and biological compatibility. To address the need for alternative carbon sources in the industrial production of BNC, this study focuses on banana leaves, discarded during harvesting, as a valuable source. Banana midrib juice, rich in nutrients and reducing sugars, is identified as a potential carbon source. An optimal culture medium was designed using a simplex-centroid mixing design and evaluated in a 10 L bioreactor. Techniques such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were used to characterize the structural, thermal, and morphological properties of BNC. Banana midrib juice exhibited specific properties, such as pH (5.64), reducing sugars (15.97 g/L), Trolox (45.07 µM), °Brix (4.00), and antioxidant activity (71% DPPH). The model achieved a 99.97% R-adjusted yield of 6.82 g BNC/L. Physicochemical analyses revealed distinctive attributes associated with BNC. This approach optimizes BNC production and emphasizes the banana midrib as a circular solution for BNC production, promoting sustainability in banana farming and contributing to the sustainable development goals.

Electrochemical performance of chemically treated pyrolytic carbon black from waste car tyres

Pyrolytic carbon black (CBp) is a solid by-product of tyre pyrolysis that contains various contaminants from the tyre additives. These contaminants limit the use of CBp as a carbon source for energy storage applications such as supercapacitors. This study aims to improve the physicochemical, morphological, and electrochemical properties of CBp by applying different chemical treatments and activation methods. The chemical treatments include acid (HCl), base (NaOH), acid-base (HCl/NaOH), and desulphurization (NaOH in xylene) processes to remove impurities such as sulphur, zinc, and silicon. The treated CBp samples are then activated by KOH impregnation technique to increase the surface area and porosity. The characterizations of the treated CBp samples are performed using Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDX), X-ray Diffraction (XRD), and Brunner Emmett Teller (BET). The electrochemical performance of the treated CBp samples are evaluated using galvanostatic charge-discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The results show that the chemical treatments significantly reduce the impurity levels and enhance the electrochemical performance of CBp. The desulphurized CBp sample exhibits the highest specific capacitance of 218 F/g among the treated CBp samples. The findings of this study suggest that CBp can be effectively utilized as a potential carbon source for supercapacitor electrodes by applying suitable chemical treatments and activation methods. This will create a circular economy to valorize CBp.

Polyhydroxyalkanoate Production from Eucalyptus Bark's Enzymatic Hydrolysate.

In recent years, polyhydroxyalkanoates (PHAs) have gained notoriety because of their desirable properties that include proven biodegradability, biocompatibility, and thermal stability, which make them suitable alternatives to fossil-based polymers. However, the widespread use of PHAs is still challenging because of their production costs, which are greatly associated with the cultivation medium used for bacterial cultivation. In Portugal, one-quarter of the forest area is covered by Eucalyptus globulus wood, making its residues a cheap, abundant, and sustainable potential carbon source for biotechnological uses. In this work, eucalyptus bark was used as the sole feedstock for PHA production in a circular bioeconomic approach. Eucalyptus bark hydrolysate was obtained after enzymatic saccharification using Cellic® CTec3, resulting in a sugar-rich solution containing glucose and xylose. Although with differing performances, several bacteria were able to grow and produce PHA with distinct compositions, using the enzymatic hydrolysate as the sole carbon source. Pseudomonas citronellolis NRRL B-2504 achieved a high cellular growth rate in bioreactor assays (24.4 ± 0.15 g/L) but presented a low accumulation of a medium-chain-length PHA (mcl-PHA) comprising the monomers hydroxydecanoate (HD, 65%), hydroxydodecanoate (HDd, 25%), and hydroxytetradecanoate (HTd, 14%). Burkholderia thailandensis E264, on the other hand, reached a lower cellular growth rate (8.87 ± 0.34 g/L) but showed a higher biopolymer accumulation, with a polyhydroxybutyrate (PHB) content in the cells of 12.3 wt.%. The new isolate, Pseudomonas sp., revealed that under nitrogen availability, it was able to reach a higher accumulation of the homopolymer PHB (31 wt.%). These results, although preliminary, demonstrate the suitability of eucalyptus bark's enzymatic hydrolysate as a feedstock for PHA production, thus offering an exciting avenue for achieving sustainable and environmentally responsible plastic products from an undervalued forestry waste.

Improvement in Electrochemical Performance of Waste Sugarcane Bagasse-Derived Carbon via Hybridization with SiO2 Nanospheres.

Sugar industries generate substantial quantities of waste biomass after the extraction of sugar water from sugarcane stems, while biomass-derived porous carbon has currently received huge research attention for its sustainable application in energy storage systems. Hence, we have investigated waste sugarcane bagasse (WSB) as a cheap and potential source of porous carbon for supercapacitors. The electrochemical capacitive performance of WSB-derived carbon was further enhanced through hybridization with silicon dioxide (SiO2) as a cost-effective pseudocapacitance material. Porous WSB-C/SiO2 nanocomposites were prepared via the in situ pyrolysis of tetraethyl orthosilicate (TEOS)-modified WSB biomass. The morphological analysis confirms the pyrolytic growth of SiO2 nanospheres on WSB-C. The electrochemical performance of WSB-C/SiO2 nanocomposites was optimized by varying the SiO2 content, using two different electrolytes. The capacitance of activated WSB-C was remarkably enhanced upon hybridization with SiO2, while the nanocomposite electrode demonstrated superior specific capacitance in 6 M KOH electrolyte compared to neutral Na2SO4 electrolyte. A maximum specific capacitance of 362.3 F/g at 0.25 A/g was achieved for the WSB-C/SiO2 105 nanocomposite. The capacitance retention was slightly lower in nanocomposite electrodes (91.7-86.9%) than in pure WSB-C (97.4%) but still satisfactory. A symmetric WSB-C/SiO2 105//WSB-C/SiO2 105 supercapacitor was fabricated and achieved an energy density of 50.3 Wh kg-1 at a power density of 250 W kg-1, which is substantially higher than the WSB-C//WSB-C supercapacitor (22.1 Wh kg-1).

Enzymatic hydrolysis of soybean hulls to produce a potential carbon source for cultivation of exopolysaccharide-producing diazotrophic bacteria

Lignocellulosic biomass, such as soybean hulls, constitutes a promising alternative substrate for application in biotechnological processes, as it is abundant, inexpensive, and renewable. However, its use is limited by the inability of bacteria and yeasts to assimilate it. To solve this problem, pretreatment and enzymatic hydrolysis conditions of soybean hulls were studied to produce a substrate capable of assimilating by exopolysaccharide-producing diazotrophic bacteria. Pretreatments by microwave (power of 1.4 kW during 30 s, 60 s, or 120 s) or autoclave (1.1 atm and 121 °C during 15 min, 30 min, or 60 min) were tested to favor the enzymatic action. Celluclast 1.5L® was used as a biocatalyst. The best results for pretreatment were obtained in an autoclave (121 °C for 15 min), with an increase of 6.7 times in the concentration of reducing sugars (40.4 g/L) in relation to hydrolysis without any previous pretreatment (6.0 g/L). The best hydrolysis conditions were established as a temperature of 50 °C, pH 5.3, and enzyme/substrate ratio of 20 FPU/g, reaching 40.4 g/L of reducing sugars. The hydrolysate was composed mainly of cellobiose, followed of glucose, xylose, and arabinose. It was used for the cultivation of Mesorhizobium sp. Semia 816, producing 1.26 g/L biomass and 3.93 g/L exopolysaccharides (EPS). An increase in viscosity with a pH decrease was observed, as well as a high degradation temperature. These results proved that soybean hull hydrolysate can be assimilated by Mesorhizobium sp. Semia 816 to produce EPS with potential industrial applications.

Recombinant Production of Pseudomonas aeruginosa Rhamnolipids in P. putida KT2440 on Acetobacterium woodii Cultures Grown Chemo-Autotrophically with Carbon Dioxide and Hydrogen.

The establishment of sustainable processes for the production of commodity chemicals is one of today's central challenges for biotechnological industries. The chemo-autotrophic fixation of CO2 and the subsequent production of acetate by acetogenic bacteria via anaerobic gas fermentation represents a promising platform for the ecologically sustainable production of high-value biocommodities via sequential fermentation processes. In this study, the applicability of acetate-containing cell-free spent medium of the gas-fermenting acetogenic bacterium A. woodii WP1 as the feeder strain for growth and the recombinant production of P. aeruginosa PAO1 mono-rhamnolipids in the well-established nonpathogenic producer strain P. putida KT2440 were investigated. Additionally, the potential possibility of a simplified production process without the necessary separation of feeder strain cells was elucidated via the cultivation of P. putida in cell-containing A. woodii culture broth. For these cultures, the content of both strains was investigated by examining the relative quantification of strain-exclusive genes via qPCR. The recombinant production of mono-rhamnolipids was successfully achieved with maximum titers of approximately 360-400 mg/L for both cell-free and cell-containing A. woodii spent medium. The reported processes therefore represent a successful proof of principle for gas fermentation-derived acetate as a potential sustainable carbon source for future recombinant rhamnolipid production processes by P. putida KT2440.

Surface-active antibiotic production as a multifunctional adaptation for postfire microorganisms.

Wildfires affect soils in multiple ways, leading to numerous challenges for colonizing microorganisms. Although it is thought that fire-adapted microorganisms lie at the forefront of postfire ecosystem recovery, the specific strategies that these organisms use to thrive in burned soils remain largely unknown. Through bioactivity screening of bacterial isolates from burned soils, we discovered that several Paraburkholderia spp. isolates produced a set of unusual rhamnolipid surfactants with a natural methyl ester modification. These rhamnolipid methyl esters (RLMEs) exhibited enhanced antimicrobial activity against other postfire microbial isolates, including pyrophilous Pyronema fungi and Amycolatopsis bacteria, compared to the typical rhamnolipids made by organisms such as Pseudomonas spp. RLMEs also showed enhanced surfactant properties and facilitated bacterial motility on agar surfaces. In vitro assays further demonstrated that RLMEs improved aqueous solubilization of polycyclic aromatic hydrocarbons, which are potential carbon sources found in char. Identification of the rhamnolipid biosynthesis genes in the postfire isolate, Paraburkholderia kirstenboschensis str. F3, led to the discovery of rhlM, whose gene product is responsible for the unique methylation of rhamnolipid substrates. RhlM is the first characterized bacterial representative of a large class of integral membrane methyltransferases that are widespread in bacteria. These results indicate multiple roles for RLMEs in the postfire lifestyle of Paraburkholderia isolates, including enhanced dispersal, solubilization of potential nutrients, and inhibition of competitors. Our findings shed new light on the chemical adaptations that bacteria employ to navigate, grow, and outcompete other soil community members in postfire environments.

Carbon and nitrogen optimization in solid-state fermentation for sustainable sophorolipid production using industrial waste.

The use of alternative feedstocks such as industrial or food waste is being explored for the sustainable production of sophorolipids (SLs). Microbial biosurfactants are mainly produced via submerged fermentation (SmF); however, solid-state fermentation (SSF) seems to be a promising alternative for using solid waste or byproducts that could not be exploited by SmF. Applying the advantages that SSF offers and with the aim of revalorizing industrial organic waste, the impact of carbon and nitrogen sources on the relationship between yeast growth and SL production was analyzed. The laboratory-scale system used winterization oil cake as the solid waste for a hydrophobic carbon source. Pure hydrophilic carbon (glucose) and nitrogen (urea) sources were used in a Box-Behnken statistical design of experiments at different ratios by applying the response surface methodology. Optimal conditions to maximize the production and productivity of diacetylated lactonic C18:1 were a glucose:nitrogen ratio of 181.7:1.43(w w-1 based on the initial dry matter) at a fermentation time of 100h, reaching 0.54 total gram of diacetylated lactonic C18:1 with a yield of 0.047g per gram of initial dry mass. Moreover, time course fermentation under optimized conditions increased the SL crude extract and diacetylated lactonic C8:1 production by 22% and 30%, respectively, when compared to reference conditions. After optimization, industrial wastes were used to substitute pure substrates. Different industrial sludges, OFMSW hydrolysate, and sweet candy industry wastewater provided nitrogen, hydrophilic carbon, and micronutrients, respectively, allowing their use as alternative feedstocks. Sweet candy industry wastewater and cosmetic sludge are potential hydrophilic carbon and nitrogen sources, respectively, for sophorolipid production, achieving yields of approximately 70% when compared to the control group.

Aluminum chloride enhances the production of short-chain fatty acids from waste activated sludge: Insights to performance, mechanism, and implications

Waste activated sludge (WAS), the major by-products during wastewater treatment, is hugely produced, which poses great environment and operation pressures. This work investigated feasibility, mechanism, and implications of aluminum chloride for carbon recovery enhancement from WAS. Results showed that aluminum chloride enhanced short-chain fatty acids (SCFAs) production potential, and the enhancement potentials were dosage dependent. The optimal dosage was 10 mg Al/g total suspended solids (TSS), with the maximum SCFAs production potential of 140 mg chemical oxygen demand/g volatile suspended solids, which was 52.2 % higher compared to that of control. Meanwhile, the compositions of SCFAs were regulated, suggesting that the recovered SCFAs were potential carbon source. Mechanism analysis showed that aluminum chloride increased the release of polysaccharides and proteins by 23.6 % and 71.7 %, respectively, compared to that in control, as well as the removal of extracellular polymeric substances to 27.5 % and the contribution of intracellular release to 38.0 %. This situation facilitated the solubilization of WAS and improved the biochemical degradability of organic matters. In addition, aluminum chloride promoted hydrolysis and acidification stages through affecting the activities of hydrolase, enriching acid-producing microorganisms, and inhibiting the activities of methanogens. This work provided some novel solutions for sludge treatment and carbon recovery, driving wastewater treatment plants to achieve carbon-neutral operation.

Temporal and spatial variation in the food web structure in artificial reef areas and adjacent habitats in Haizhou Bay

Artificial reef is regarded as an effective tool for restoring habitats and supporting the marine ecosystem. While the energy flow and material exchange in the food web of artificial reef ecosystem still remain vacant and should be further understood. In this study, stable isotopic characteristics (δ13C and δ15N) were used to identify the trophic niches and potential carbon sources of consumers (fish and invertebrates) in artificial reef areas and adjacent habitats in Haizhou Bay (the estuary area (EA), the aquaculture area (AA), the artificial reef area (AR), the natural area (NA) and the comprehensive effect area (CEA)) in spring and autumn. The results showed that the average δ13C for all consumers decreased from − 16.99 ± 2.07‰ to − 21.81 ± 1.66‰, and the average δ15N ranged from 11.37 ± 0.35‰ to 14.69 ± 0.64‰ in all seasons. A SIBER model revealed highly similar trophic niche among habitats in autumn, and lower overlap in spring. The SIMMR model showed that phytoplankton and sedimentary organic matter (SOM) were the major contributors to consumers, and particulate organic matter (POM) accounted for less contribution. In AA and NA phytoplankton and SOM generally contributed fairly equally to most fish, while single SOM sources were major contributors to nearly all the species in AR and CEA. Our findings reveal that ARs can serve as seascape mosaics to increase fish community diversity because of their high variation in the δ13C value and the trophic niches from EA to the NA. Preliminary multidisciplinary studies are needed for the mitigation of effects before any implementations deployed to the offshore waters that influence habitat connectivity, especially some habitat–specific migratory species.

Unveiling the spatial patterns and potential sources of black carbon in lake sediments from diverse developing areas in a representative mining and metallurgy region of Central China

Unveiling the spatial patterns and potential sources of black carbon in lake sediments from diverse developing areas in a representative mining and metallurgy region of Central China

High-performance chlorinated polyvinyl chloride/polyurea nanocomposite foam with excellent solvent resistance, flame-triggered shape memory effect and its upcycling

Facing the global environmental pollution crisis related to waste plastics, the recyclable design of polymer materials and composites, especially large commodities, is the most effective and fundamental solution. Herein, an upcycling chlorinated polyvinyl chloride/polyurea (CPVC/PUA) nanocomposite foam was designed by means of the “plasticizing-foaming-reinforcing” (PFR) strategy combined with catalytic carbonization of CPVC/PUA foams. On one hand, the foam with ultra-high expansion ratio (62 times) can be facilely prepared in supercritical CO2 at lower temperature, benefited of the reactive plasticizing function of PUA monomer-polymeric methylene diphenyldiisocyanate (PMDI). On the other hand, the obtained foam is reinforced by PMDI crosslinking reaction to in situ form nano-PUA phase in the CPVC matrix and realizing robust and superior solvent resistance and flame-triggered shape memory effect. Moreover, the foam possesses remarkable ablation resistance, which is attributed to super carbonization capacity of CPVC catalyzed by PUA. This carbonization behavior endows the foam directly upcycle into functional carbon foam accompanied by the formation of HCl gas and functional aromatics. The obtained carbon foam shows attractive electromagnetic interference shielding performance, which also may be used as potential carbon source or catalyst of producing vinyl chloride monomer in the chlor-alkali industry, especially in China.

Applying sludge hydrolysate as a carbon source for biological denitrification after composition optimization via red soil filtration

Sludge hydrolysate, the byproduct generated during sludge hydrothermal treatment (HT), is a potential carbon source for biological denitrification. However, the refractory organic matters and the nutrient substances are unfavorable to the nitrogen removal. In this study, effects of HT conditions on the hydrolysate properties, and the hydrolysate compositions optimization via red soil (RS) filtration were investigated. At HT temperature of 160–220 °C and reaction time of 1–4 h, the highest dissolution rate of organics from sludge to hydrolysate achieved 70.1 %, while the acetic acid dominated volatile fatty acids (VFAs) was no more than 5.0 % of the total organic matter content. The NH4+-N and dissolved organic nitrogen (DON) were the main nitrogen species in hydrolysate. When the hydrolysate was filtered by RS, the high molecular weight organic matters, DON, NH4+ and PO43− were effectively retained by RS, while VFAs and polysaccharide favorable for denitrification were kept in the filtrate. When providing same COD as the carbon source, the filtrate group (Fi-Group) introduced lower concentrations of TN and humic substances but higher content of VFAs. This resulted in TN removal rate (57.0 %) and denitrification efficiency (93.6 %) in Fi-Group higher than those in hydrolysate group (Hy-Group), 39.4 % and 83.7 %, respectively. It is noticeable that both Hy- and Fi- Groups up-regulated most of denitrification functional genes, and increased the richness and diversity of denitrifying bacteria. Also, more denitrifying bacteria genera appeared, and their relative abundance increased significantly from 3.31 % in Control to 21.15 % in Hy- Group and 31.31 % in Fi-Group. This indicates that the filtrate is a more suitable carbon source for denitrification than hydrolysate. Moreover, the pH rose from 4.6 ± 0.14 to 6.5 ± 0.05, and the organic carbon, TN, TP and cation exchange capacity (CEC) of RS increased as well after being filtered, implying that the trapped compounds may have the potential to improve soil quality. This study provides a new insight for hydrolysate application according to its composition characteristics, and helps make the most use of wasted sludge.