Effect of nanobubble water on medium chain carboxylic acids production in anaerobic digestion of cow manure.

Nanobubble water promotes the degradation of difficult-to-degrade organic matter, improves the activity of electron transfer systems during anaerobic digestion, and optimizes the composition of anaerobic microbial communities. Therefore, this study proposes the use of nanobubble water to improve the yield of medium chain carboxylic acids produced from cow manure by chain elongation. The experiment was divided into two stages: the first stage involved the acidification of cow manure to produce volatile acidic fatty acids as electron acceptors, and the second phase involved the addition of lactic acid as an electron donor for the chain elongation. Three experimental groups were established, and air, H2, and N2 nanobubble water were added in the second stage. Equal amounts of deionized water were added in the control group. The results showed that nanobubble water supplemented with air significantly increased the caproic acid concentration to 15.10 g/L, which was 55.03 % greater than that of the control group. The relative abundances of Bacillus and Caproiciproducens, which are involved in chain elongation, and Syntrophomonas, which is involved in electron transfer, increased. The unique ability of air nanobubble water supplemented to break down the cellulose matrix resulted in further decomposition of the recalcitrant material in cow manure. This effect subsequently increased the number of microorganisms associated with lignocellulose degradation, increasing carbohydrate metabolism and ATP-binding cassette transporter protein activity and enhancing fatty acid cycling pathways during chain elongation. Ultimately, this approach enabled the efficient production of medium chain carboxylic acids.

Novel material-oriented valorization of biogas can achieve more carbon reduction than traditional utilization by bioelectricity or biomethane.

Two novel biogas upgrading strategies that recover high-value chemicals or CO2 liquid fertilizer from biogas besides biomethane were evaluated from the view of global warming potential (GWP) through life cycle assessment in comparison with conventional approaches. Results show that the scenarios producing biomethane with nano calcium carbonate or CO2 liquid fertilizer from biogas present significantly lower GWP (-3.4 kgCO2-eq/Nm3-biogas and -4.4 kgCO2-eq/Nm3-biogas, respectively), compared to combined heat and power scenario (-2.4 kgCO2-eq/Nm3-biogas) and biogas upgrading by high pressure water scrubbing scenario (-1.3 kgCO2-eq/Nm3-biogas). The carbon sequestration and utilization from CO2-rich water significantly enhanced carbon reduction in overall biogas management. Furthermore, considering cleaner electricity in the future, strategies focusing on managing biogas for materials will align more with climate change goals than energy-focused strategies. This study provides insight for decision-makers in developing roadmaps for carbon reduction pathways in biogas-relating sectors.

Interfacial Modulation of a Self-Sacrificial Synthesized SnO2@Sn Core-Shell Heterostructure Anode toward High-Capacity Reversible Li+ Storage.

Sn-based anodes are promising high-capacity anode materials for low-cost lithium ion batteries. Unfortunately, their development is generally restricted by rapid capacity fading resulting from large volume expansion and the corresponding structural failure of the solid electrolyte interphase (SEI) during the lithiation/delithiation process. Herein, heterostructural core-shell SnO2-layer-wrapped Sn nanoparticles embedded in a porous conductive nitrogen-doped carbon (SOWSH@PCNC) are proposed. In this design, the self-sacrificial Zn template from the precursors is used as the pore former, and the LiF-Li3N-rich SEI modulation layer is motivated to average uniform Li+ flux against local excessive lithiation. Meanwhile, both the chemically active nitrogen sites and the heterojunction interfaces within SnO2@Sn are implanted as electronic/ionic promoters to facilitate fast reaction kinetics. Consequently, the as-converted SOWSH@PCNC electrodes demonstrate a significantly boosted Li+ capacity of 961 mA h g-1 at 200 mA g-1 and excellent cycling stability with a low capacity decaying rate of 0.071% after 400 cycles at 500 mA g-1, suggesting their great promise as an anode material in high-performance lithium ion batteries.

Effects of hydrochar and biogas slurry reflux on methane production by mixed anaerobic digestion of cow manure and corn straw.

This study aimed to enhance methane production from mixed anaerobic digestion of cow manure and corn straw by adding hydrochar and biogas slurry reflux. The hydrochar characterization revealed that it can provide attachment for microbial growth, and abundant surface functional groups (such as C-O, CO, C-OH, and C-N) for adsorption. Direct interspecies electron transfer (DIET) mediated by surface oxygen-containing functional groups on hydrochar increased the methane yield. The experimental group added with hydrochar and biogas slurry reflux had the highest methane and biogas production (34.40% and 36.98% higher than the control group, respectively). Results demonstrate hydrochar and biogas slurry reflux can improve microorganism species richness in anaerobic digestion systems, in which hydrochar can also improve microorganism species uniformity. Distance-based redundancy analysis showed that the VFAs, and pH had the greatest effects on the composition of the microbial community. The dominant microorganism at the phylum level in AD system were Bacteroidetes, Firmicutes, and Proteobacteria. The addition of hydrochar and biogas slurry reflux can significantly increase the species abundance of Methanobacterium. These results indicate that the addition of hydrochar and biogas slurry reflux can improve the corresponding microbial abundance, in which hydrochar can enhance the redox characteristics and DIET between microorganism, biogas slurry reflux can also increase nutrient content of anaerobic digestion system, and collectively promote the methane yield.

Applying mixotrophy strategy to enhance biomass production and nutrient recovery of Chlorella pyrenoidosa from biogas slurry: An assessment of the mixotrophic synergistic effect.

Using biogas slurry to cultivate microalgae can simultaneously obtain microalgal biomass and allow nutrient recovery. Mixotrophic microalgae are widely recognized for their high biomass accumulation and low light dependence, making it possible to overcome the drawbacks of photoautotrophy. In this study, three complete metabolic modes of photoautotrophy, heterotrophy, mixotrophy and two incomplete metabolic modes with the addition of diuron and rotenone were applied to investigate Chlorella pyrenoidosa growth in biogas slurry. The results showed that the mixotrophic group obtained 1.15 g/L biomass, 30 % starch content, 99.40 % ammonium removal and 81.69 % total phosphorus removal, which were highly promoted compared to the others. The decline in chlorophyll, the simultaneous downregulation of Rubisco and citrate synthase and the increase in the actual quantum yield of PSII under mixotrophy revealed a synergistic effect: the complementation of photophosphorylation and oxidative phosphorylation greatly contributed to maximizing energy metabolism efficiency and minimizing energy dissipation loss.

Enhanced Anaerobic Biogas Production From Wheat Straw by Herbal-Extraction Process Residues Supplementation.

Trace metals are essential constituents of cofactors and enzymes and that their addition to anaerobic digesters increases methane production. Many trace elements are contained in herbal-extraction process residues (HPR). The present study concerns the effect of six kinds of HPR [Danshen root (Dr), Astragalus membranaceus (Am), Isatis root (Ir), Angelica sinensis (As), and Pseudo-ginseng (Pg)] that were used as additives, respectively, in the anaerobic digestion of wheat straw on biogas and methane production. The ratios of HPR residues/wheat straw [based on total solids (TS), of wheat straw] were 3, 5, and 10%, respectively. The digesters were at 37 ± 1°C of water bath during 30 days of anaerobic digestion. The results showed that HPR had significant effects on the anaerobic co-digestion. The highest biogas productivity was achieved when treated with 10% Pseudo-ginseng residues (PGR), which yielded 337 ml/g TS of biogas and 178 ml/g TS of methane. Cumulative production of biogas and methane increased by 28 and 37% compared to the production achieved in the control. These results suggest that PGR is an effective HPR to enhance the production of methane.

Long-Life Dendrite-Free Lithium Metal Electrode Achieved by Constructing a Single Metal Atom Anchored in a Diffusion Modulator Layer.

Lithium metal electrodes have shown great promise for high capacity and the lowest potential. However, wide application is restricted by uncontrollable plating/stripping lithium behaviors, an uneven solid electrolyte interphase, and a lithium dendrite. Herein, the highly active single metal atom anchored in vacant catalyst is synthesized on the hierarchical porous nanocarbon (SACo/ADFS@HPSC). Acting as an artificial protective modulation layer on the lithium surface, the numerous atomic sites show the superiority in modulating lithium ion behaviors and smoothing the lithium surface without dendrite growth. As a consequence, the SACo/ADFS@HPSC-modified Li electrode lowers nucleation barrier (15 mV), extends the smooth plating lifespan (1600 h), and improves Coulombic efficiency, significantly accelerating the horizonal deposition of plated lithium. Coupled with a sulfur cathode, the fabricated pouch cell with 5.4 mg cm-2 delivers a high capacity of 3.78 mA h cm-2 corresponding to 1505 Wh kg-1, showing the promising practical application.

Relieving ammonia nitrogen inhibition in high concentration anaerobic digestion of rural organic household waste by Prussian blue analogue nanoparticles addition.

The application of Prussian blue analogue nanoparticles in anaerobic digestion was firstly used to evaluate the removal effect of ammonia nitrogen inhibition in anaerobic digestion. We have successfully prepared Prussian blue analogue nanoparticles, which has a high adsorption capacity of ammonia nitrogen in anaerobic digestion is 71.09 mg/g. The high concentration anaerobic digestion of rural organic household waste was not successful because of the serious inhibition of ammonia nitrogen. After adding Prussian blue analogue nanoparticles, the methane production of each group increased greatly, up to 302.22 ml/gVS. The concentration of ammonia nitrogen in anaerobic digestion decreased to 1700.77 mg/l. Prussian blue analogue nanoparticles have a good application prospect in high concentration anaerobic digestion of rural organic household waste enriched with a high concentration of ammonia nitrogen.

Improving the fermentable sugar yields of wheat straw by high-temperature pre-hydrolysis with thermophilic enzymes of Malbranchea cinnamomea.

BACKGROUND: Enzymatic hydrolysis is a key step in the conversion of lignocellulosic polysaccharides to fermentable sugars for the production of biofuels and high-value chemicals. However, current enzyme preparations from mesophilic fungi are deficient in their thermostability and biomass-hydrolyzing efficiency at high temperatures. Thermophilic fungi represent promising sources of thermostable and highly active enzymes for improving the biomass-to-sugar conversion process. Here we present a comprehensive study on the lignocellulosic biomass-degrading ability and enzyme system of thermophilic fungus Malbranchea cinnamomea N12 and the application of its enzymes in the synergistic hydrolysis of lignocellulosic biomass. RESULTS: Malbranchea cinnamomea N12 was capable of utilizing untreated wheat straw to produce high levels of xylanases and efficiently degrading lignocellulose under thermophilic conditions. Temporal analysis of the wheat straw-induced secretome revealed that M. cinnamomea N12 successively degraded the lignocellulosic polysaccharides through sequential secretion of enzymes targeting xylan and cellulose. Xylanase-enriched cocktail from M. cinnamomea N12 was more active on native and alkali­pretreated wheat straw than the commercial xylanases from Trichoderma reesei over temperatures ranging from 40 to 75 °C. Integration of M. cinnamomea N12 enzymes with the commercial cellulase preparation increased the glucose and xylose yields of alkali­pretreated wheat straw by 32 and 166%, respectively, with pronounced effects at elevated temperature. CONCLUSIONS: This study demonstrated the remarkable xylanase-producing ability and strategy of sequential lignocellulose breakdown of M. cinnamomea N12. A new process for the hydrolysis of lignocellulosic biomass was proposed, comprising thermophilic enzymolysis by enzymes of M. cinnamomea N12 followed with mesophilic enzymolysis by commercial cellulases. Developing M. cinnamomea N12 as platforms for thermophilic enzyme mixture production will provide new perspectives for improved conversion yields for current biomass saccharification schemes.

Parvibaculum sedimenti sp. nov., A Novel Soil Bacterium Isolated from Sediment.

A Gram-stain-negative, aerobic bacterium, designated HXT-9T, was isolated from a river sediment. Cells were rod-shaped and non-motile. Growth occurred at 10-42 ℃ (optimum 30 ℃), at pH 5.0-8.0 (optimum pH 7.0) and with NaCl concentrations of 0-2.5% (optimum 0.5%). Phylogenetic trees based on 16S rRNA gene sequences showed that strain HXT-9T belonged to the genus Parvibaculum, and showed highest similarities to P. lavamentivorans KCTC 22775T (96.1%), followed by P. hydrocarboniclasticum EPR 92T (94.8%) and P. indicum P31T (93.6%). The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain HXT-9T and P. lavamentivorans KCTC 22775T were 75.2% and 20.8%, respectively. The G + C content of strain HXT-9T genome was 62.1 mol%. The major fatty acids (> 10%) were summed feature 8 (C18:1ω7c and/or C18:1ω6c), C19:0 cyclo ω8c and C16:0 3-OH. The major respiratory quinone was ubiquinone 11 (Q-11). The major polar lipids were DPG (diphosphatidylglycerol), PG (phosphatidylglycerol), PME (phosphatidylmonomethylethanolamine), PE (phosphatidylethanolamine), PC (phosphatidylcholine) and AL (unidentified aminolipids). The phylogenetic analysis and physiological and biochemical data showed that strain HXT-9T represents a novel species in the genus Parvibaculum, for which the name P. sedimenti sp. nov. is proposed. The type strain is HXT-9T (= CCTCC AB 2019273T = KCTC 72547T).

Enhanced methane production from wheat straw with the assistance of lignocellulolytic microbial consortium TC-5.

The major obstacle of methane production from lignocellulose lies in the inefficient deconstruction of biomass. In this study, an anaerobic microbial consortium TC-5 was enriched with high lignocellulose-degradation capacity to enhance methane production from wheat straw. High degradation ratio of 45.7% of un-pretreated wheat straw was achieved due to a multi-species lignocellulolytic enzyme presented in the crude culture supernatant. The specific activity of xylanase, xylan esterase and ß-xylosidase reached the highest level of 4.23, 0.15 and 0.48 U/mg, while cellobiohydrolase, endoglucanase and ß-glucosidase showed the highest specific activity of 0.36, 0.22 and 0.41 U/mg during 9 days' degradation. Inoculation of TC-5 in digestion sludge during anaerobic digestion of wheat straw resulted in remarkable enhancement of 22.2% and 36.6% in methane yield under mesophilic and thermophilic conditions, respectively. This work demonstrates the potential of TC-5 for enhancing the production of biogas and other chemicals through biomass based biorefinery.

Ultra-small Nd(3+)-doped nanoparticles as near-infrared luminescent biolabels of hemin in bacteria.

Near-infrared (NIR) luminescent Nd(3+)-doped nanoparticles (NPs) have attracted considerable attention in bioimaging and biodetection. Here, we demonstrate sub-6 nm NaGdF4:Nd(3+),Fe(3+) NPs as luminescent biolabels of hemin molecules that act as the exogenous electron carriers in microbial communities. Contrary to the severe quenching of the visible luminescence for either upconverting or downconverting NPs, the Nd(3+)-doped NPs show superior properties in avoiding the optical absorption of hemin within the UV and visible spectral regions. A detailed examination showed that the Nd(3+)-doped NPs exhibit no obvious toxic effects on the microbial communities and show scarce influence on the characteristics of labeled hemin molecules in enhancing the reducing power of the fermentation system. More importantly, by monitoring the NIR luminescence of Nd(3+)-doped NPs, the selective accumulation of exogenous electron carriers in bacteria that are lacking reducing power has been revealed for the first time. The application of Nd(3+)-doped NPs as biolabels in bacteria would provide new opportunities for further unravelling the role of exogenous electron carriers in anaerobic digestion.

Methane production from wheat straw with anaerobic sludge by heme supplementation.

Wheat straw particles were directly used as substrate for batch anaerobic digestion with anaerobic sludge under 35°C to evaluate the effects of adding heme on methane production. When 1mg/l heme was added to the fermentation process with no agitated speed, a maximum cumulative methane production of 12227.8ml was obtained with cumulative methane yield of wheat straw was 257.4ml/g-TS (total solid), which was increased by 20.6% compared with 213.5ml/g-TS of no heme was added in the reactor. Meanwhile, oxido-reduction potential (ORP) level was decreased, the activity of coenzyme F420 was significantly improved and NADH/NAD(+) ratio were the highest than other experimental groups. These results suggest that heme-supplemented anaerobic sludge with no agitated speed may be providing a more reductive environment, which is a cost-effective method of anaerobic digestion from biomass waste to produce methane with less energy consuming.

Succinic acid production from sucrose by Actinobacillus succinogenes NJ113.

In this study, sucrose, a reproducible disaccharide extracted from plants, was used as the carbon source for the production of succinic acid by Actinobacillus succinogenes NJ113. During serum bottle fermentation, the succinic acid concentration reached 57.1g/L with a yield of 71.5%. Further analysis of the sucrose utilization pathways revealed that sucrose was transported and utilized via a sucrose phosphotransferase system, sucrose-6-phosphate hydrolase, and a fructose PTS. Compared to glucose utilization in single pathway, more pathways of A. succinogenes NJ113 are dependent on sucrose utilization. By changing the control strategy in a fed-batch culture to alleviate sucrose inhibition, 60.5g/L of succinic acid was accumulated with a yield of 82.9%, and the productivity increased by 35.2%, reaching 2.16g/L/h. Thus utilization of sucrose has considerable potential economics and environmental meaning.

Ultrasonic pretreatment and acid hydrolysis of sugarcane bagasse for succinic acid production using Actinobacillus succinogenes.

Immense interest has been devoted to the production of bulk chemicals from lignocellulose biomass. Diluted sulfuric acid treatment is currently one of the main pretreatment methods. However, the low total sugar concentration obtained via such pretreatment limits industrial fermentation systems that use lignocellulosic hydrolysate. Sugarcane bagasse hemicellulose hydrolysate is used as the carbon and nitrogen sources to achieve a green and economical production of succinic acid in this study. Sugarcane bagasse was ultrasonically pretreated for 40 min, with 43.9 g/L total sugar obtained after dilute acid hydrolysis. The total sugar concentration increased by 29.5 %. In a 3-L fermentor, using 30 g/L non-detoxified total sugar as the carbon source, succinic acid production increased to 23.7 g/L with a succinic acid yield of 79.0 % and a productivity of 0.99 g/L/h, and 60 % yeast extract in the medium could be reduced. Compared with the detoxified sugar preparation method, succinic acid production and yield were improved by 20.9 and 20.2 %, respectively.

Succinic acid production by Actinobacillus succinogenes NJ113 using corn steep liquor powder as nitrogen source.

In this study, corn steep liquor powder (CSL) was used as nitrogen source to replace the relatively costly yeast extract typically used for the production of succinic acid with Actinobacillus succinogenes NJ113. Moreover, when heme was added to the fermentation medium and the culture was agitated at a low speed, a maximum succinic acid concentration of 37.9 g/l was obtained from a glucose concentration of 50 g/l, and a productivity of 0.75 g/l/h was achieved. These yields are almost as high as for fermentation with glucose and yeast extract. These results suggest that heme-supplemented CSL may be a suitable alternative nitrogen source for a cost-effective method of producing succinic acid with A. succinogenes NJ113 while consuming less energy than previous methods.

Succinic acid production from cellobiose by Actinobacillus succinogenes.

In this study, cellobiose, a reducing disaccharide was used to produce succinic acid by Actinobacillus succinogenes NJ113. A final succinic acid concentration of 30.3g/l with a yield of 67.8% was achieved from an initial cellobiose concentration of 50 g/l via batch fermentation in anaerobic bottles. The cellobiose uptake mechanism was investigated and the results of enzyme assays revealed that the phosphoenolpyruvate phosphotransferase system (PEP-PTS) played an important role in the cellobiose uptake process. In batch fermentation with 18 g/l of cellobiose and 17 g/l of other sugars from sugarcane bagasse cellulose hydrolysates, a succinic acid concentration of 20.0 g/l was obtained, with a corresponding yield of 64.7%. This study found that cellobiose from incomplete hydrolysis of cellulose could be a potential carbon source for economical and efficient succinic acid production by A. succinogenes.

Clostridium beijerinckii mutant obtained by atmospheric pressure glow discharge producing high proportions of butanol and solvent yields.

With 30 g glucose/l as carbon source, Clostridium beijerinckii ART124, a mutant created by atmospheric pressure glow discharge, produced 13.7 g total solvent/l (containing 3.1 g acetone/l, 10.4 g butanol/l and 0.2 g ethanol/l) in 72 h. The mutant could also use sucrose or xylose or a mixture of glucose/xylose/arabinose with nearly equal yields.

Influence of osmotic stress on fermentative production of succinic acid by Actinobacillus succinogenes.

This study investigated the influence of osmotic stress on succinic acid production by Actinobacillus succinogenes NJ113. Both cell growth and succinic acid production were inhibited with the increase in osmotic stress of the medium. The use of three different osmoprotectants in the production of succinic acid was studied in order to decrease the inhibitory effects of osmotic stress during fermentation. Results indicated that proline offers optimal osmoprotection in the production of succinic acid by A. succinogenes NJ113. In tests of batch fermentation, the maximum cell concentration was observed to be 5.36 g DCW/L after the addition of 25 mmol/L proline to the fermentation medium. The cell concentration was 24% higher than that noted for the control. A total quantity of 56.2 g/L of succinic acid was produced, with a production rate of 1 g/L per hour, after 56 h of fermentation. The concentration and productivity of succinic acid was observed to be increased by 22.2% and 22%, respectively, as compared with the control. The specific activity levels of key enzymes in the metabolic network was noted to be higher following the addition of proline, particularly in the later stages of fermentation. This method of enhancing succinic acid production by the addition of an osmoprotectant may potentially provide an alternative approach for enhanced production of other organic acids.

Optimization of culture conditions in CO2 fixation for succinic acid production using Actinobacillus succinogenes.

The culture conditions in CO(2) fixation by Actinobacillus succinogenes for succinic acid production were investigated by a model of available CO(2) in a 3-l fermentor. The results from the model analysis showed that the available CO(2) for succinic acid production in the fermentation broth is the sum of HCO(3) (-), CO(3) (2-), and CO(2) influenced by external culture conditions such as medium components, CO(2) partial pressures, and temperature. The optimized conditions for CO(2) supply in a 3-l fermentor were determined as follows: CO(2) partial pressure and stirring speed were maintained at 0.1 MPa and 200 r min(-1), respectively, with a pH of 6.8 and a temperature of 37°C; 0.15 mol l(-1) NaHCO(3) was added. Under the optimized conditions, a CO(2) fixation rate of 0.57 g l(-1) h(-1) was obtained, and a succinic acid concentration of 51.6 g l(-1) with a yield of 75.8% was reached. These results suggest that optimized conditions of CO(2) supply are effective in high succinic acid production and thus have potential applications in succinic acid production and CO(2) fixation.