Graphene oxide (GO) prepared from graphite powder using a modified Hummers method and reduced graphene oxide (rGO) obtained from GO using different reductants, i.e., sodium borohydride, hydrazine, ...formaldehyde, sodium hydroxide and L-ascorbic acid, were investigated using transmission electron microscopy, X-ray diffraction, Raman, infrared and electron spectroscopic methods. The GO and rGOs’ stacking nanostructure (flake) size (height x diameter), interlayer distance, average number of layers, distance between defects, elementary composition, content of oxygen groups, C sp
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and vacancy defects were determined. Different reductants applied to GO led to modification of carbon to oxygen ratio, carbon lattice (vacancy) and C sp
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defects with various in-depth distribution of C sp
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due to oxygen group reduction proceeding as competing processes at different rates between interstitial layers and in planes. The reduction using sodium borohydride and hydrazine in contrary to other reductants results in a larger content of vacancy defects than in GO. The thinnest flakes rGO obtained using sodium borohydride reductant exhibits the largest content of vacancy, C sp
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defects and hydroxyl group accompanied by the smallest content of epoxy, carboxyl and carbonyl groups due to a mechanism of carbonyl and carboxyl group reduction to hydroxyl groups. This rGO similar diameter to GO seems to result from a predominant reduction rate between the interstitial layers. The thicker flakes of a smaller diameter than in GO are obtained in rGOs prepared using remaining reductants and result from a higher rate of reduction of in plane defects.
Intercropping heavy metal hyperaccumulators and low-accumulating cultivars is a promising strategy for remediating contaminated soils without impeding agricultural production. A field plot experiment ...was conducted to explore the effects of intercropping maize with Brassica juncea L. on the rhizosphere microecological properties, plant growth and cadmium (Cd) accumulation. The results showed that the Cd bioaccumulation amount per unit area (BCAarea) of the intercropping system was 12.9% lower than that of the Brassica juncea L. monoculture but 87.5% higher than that of the maize monoculture. The grain yield of maize was increased by 10.5% through intercropping, and the land equivalent ratio (LER) was greater than 1. Soil available Cd in intercropped maize was 13.4% lower than that in monoculture maize but was 12.7% higher in intercropped Brassica juncea L. than in monoculture Brassica juncea L. Intercropping significantly increased the contents of malic acid and citric acid in the rhizospheres of maize and Brassica juncea L. The dominant microorganisms were similar in all studied soils but were different in relative abundance between the intercropping and monoculture treatments. These findings suggest that intercropping maize with Brassica juncea L. could be a promising approach for phytoremediation without reducing crop yield in Cd-contaminated soil.
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•Intercropping with Brassica juncea L. reduced grain Cd and increased yield of maize•Cd accumulation of Brassica juncea L. in intercropping was higher than monoculture•Low soil pH increased available Cd in intercropping Brassica juncea L. rhizosphere•Competitive absorption decreased available Cd in the intercropped maize rhizosphere•Root exudates was the main factor influencing soil bacteria in intercropping system
•A fed batch fermentation strategy was designed for Ralstonia eutropha using organic acids as feedstock.•Organic acids were fed by pH-stat, and organic acid salts were fed using pO2-dependent feed ...control.•A fed batch strategy using three successive carbon/nitrogen ratios (10, 90, to infinite) was employed to maximize PHA productivity.•Biomass yield of 112.0g/L, PHA yield of 93.5g/L, and a PHA productivity of 2.13g/L/h was achieved using the strategy outlined in this work.
The utilization of inexpensive carbon sources, including waste streams, for production of value added products has been explored for over two decades. Palm oil mill effluent (POME), a waste water stream from the palm oil industry, can be used to produce organic acids and their salts by anaerobic digestion. These organic acids are suitable as the main carbon source for growth and production of polyhydroxyalkanoates (PHAs) by organisms like Ralstonia eutropha. The presence of propionate/propionic acid results in the biosynthesis of the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) P(HB-co-HV), which is desired for its favourable thermal and mechanical properties compared to the polyhydroxybutyrate (PHB) homopolymer. A specially-designed fed-batch strategy is necessary to decrease the toxic effects of organic acids in cultures of R. eutropha. A pH-stat fed-batch culture technique, using organic acids as the main carbon source, was adopted in combination with an additional pO2-dependent feed for delivering organic acid salts. The developed strategy is highly reproducible and shows a high productivity of >2g PHA/L/h. After 44h of fermentation, 112.4±2.3g/L cell dry weight (CDW) with 83.3±1.1% P(HB-co-HV)/CDW containing 5.6±0.4mol% 3-hydroxyvalerate (3HV) were achieved. The described productivity, CDW and P(HB-co-HV)/CDW values are by far the highest reported results for R. eutropha cultivated on mixed organic acids as the main carbon source.
The rapid industrialization and economic development in the Pearl River Delta (PRD) region of southern China have led to a substantial increase in anthropogenic emissions and hence frequent haze ...pollution over the past two decades. In early January 2017, a severe regional haze pollution episode was captured in the PRD region, with a peak PM2.5 concentration of around 400μgm−3, the highest value ever reported at this site. During the haze episode, elevated concentrations of oxygenated volatile organic compounds (OVOCs, 33±16 ppbv) and organic matter (41±15μg m−3) were observed, indicating the enhanced roles of secondary organic aerosols (SOAs) in the formation of haze pollution. Water-soluble organic carbon (WSOC, 12.8±5.5μg C m−3) dominated the organic aerosols, with a WSOC/OC ratio of 0.63±0.12 and high correlation (R=0.85) with estimated secondary organic carbon (SOC), suggesting the predominance of a secondary origin of the measured organic aerosols during the haze episode. Four carboxylic acids (oxalic, acetic, formic, and pyruvic acids) were characterized in the aerosols (1.30±0.38μgm−3) and accounted for 3.6±1.2% of WSOC in carbon mass, with oxalic acid as the most abundant species. The simultaneous measurements of volatile organic compounds (VOCs), OVOCs, and organic acids in aerosols at this site provided an opportunity to investigate the relationship between the precursors and the products, as well as the potential formation pathways. Water-soluble aldehydes and ketones, predominantly produced via the oxidation of anthropogenic VOCs (mainly propane, toluene, n-butane, and m, p-xylene), were the main contributors of the organic acids. The formation of OVOCs is largely attributed to gas-phase photochemical oxidation, whereas the WSOC and dicarboxylic acids were produced from both photochemistry and nocturnal heterogeneous reactions. These findings provided further insights into the oxidation and evolution of organic compounds during the haze pollution episode.
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•Simultaneous measurement of VOCs, OVOCs, and organic aerosol during a haze episode•Enhanced contribution of oxygenated organic matter in haze pollution•Secondary formation of OVOCs from industrial solvent and traffic-emitted VOCs•Photochemical and nocturnal heterogeneous processes are of comparable significance.•Aldehydes and ketones from VOCs oxidation are the main precursors of organic acids.
With the increase in regulations regarding the use of antibiotic growth promoters and the rise in consumer demand for poultry products from 'Raised Without Antibiotics' or 'No Antibiotics Ever' ...flocks, the quest for alternative products or approaches has intensified in recent years. A great deal of research has focused on the development of antibiotic alternatives to maintain or improve poultry health and performance. This review describes the potential for the various alternatives available to increase animal productivity and help poultry perform to their genetic potential under existing commercial conditions. The classes of alternatives described include probiotics, prebiotics, synbiotics, organic acids, enzymes, phytogenics, antimicrobial peptides, hyperimmune egg antibodies, bacteriophages, clay, and metals. A brief description of the mechanism of action, efficacy, and advantages and disadvantages of their uses are also presented. Though the beneficial effects of many of the alternatives developed have been well demonstrated, the general consensus is that these products lack consistency and the results vary greatly from farm to farm. Furthermore, their mode of action needs to be better defined. Optimal combinations of various alternatives coupled with good management and husbandry practices will be the key to maximize performance and maintain animal productivity, while we move forward with the ultimate goal of reducing antibiotic use in the animal industry.
Crop yields are significantly reduced by aluminum (Al) toxicity on acidic soils, which comprise up to 50% of the world's arable land. Al-activated release of ligands (such as organic acids) from the ...roots is a major Al tolerance mechanism in plants. In maize, Al-activated root citrate exudation plays an important role in tolerance. However, maize Al tolerance is a complex trait involving multiple genes and physiological mechanisms. Recently, transporters from the MATE family have been shown to mediate Al-activated citrate exudation in a number of plant species. Here we describe the cloning and characterization of two MATE family members in maize, ZmMATE1 and ZmMATE2, which co-localize to major Al tolerance QTL. Both genes encode plasma membrane proteins that mediate significant anion efflux when expressed in Xenopus oocytes. ZmMATE1 expression is mostly concentrated in root tissues, is up-regulated by Al and is significantly higher in Al-tolerant maize genotypes. In contrast, ZmMATE2 expression is not specifically localized to any particular tissue and does not respond to Al. ¹⁴C-citrate efflux experiments in oocytes demonstrate that ZmMATE1 is a citrate transporter. In addition, ZmMATE1 expression confers a significant increase in Al tolerance in transgenic Arabidopsis. Our data suggests that ZmMATE1 is a functional homolog of the Al tolerance genes recently characterized in sorghum, barley and Arabidopsis, and is likely to underlie the largest maize Al tolerance QTL found on chromosome 6. However, ZmMATE2 most likely does not encode a citrate transporter, and could be involved in a novel Al tolerance mechanism.
Sesame is an important oil crop due to its high oil, antioxidant, and protein content. Drought stress is a major abiotic stress that affects sesame production as well as the quality of sesame seed. ...To reveal the adaptive mechanism of sesame in response to water deficient conditions, transcriptomic and metabolomics were applied in drought-tolerant (DT) and drought-susceptible (DS) sesame genotypes.
Transcriptomic analysis reveals a set of core drought-responsive genes (684 up-regulated and 1346 down-regulated) in sesame that was robustly differently expressed in both genotypes. Most enriched drought-responsive genes are mainly involved in protein processing in endoplasmic reticulum, plant hormone signal transduction photosynthesis, lipid metabolism, and amino acid metabolism. Drought-susceptible genotype was more disturbed by drought stress at both transcriptional and metabolic levels, since more drought-responsive genes/metabolites were identified in DS. Drought-responsive genes associated with stress response, amino acid metabolism, and reactive oxygen species scavenging were more enriched or activated in DT. According to the partial least-squares discriminate analysis, the most important metabolites which were accumulated under drought stress in both genotypes includes ABA, amino acids, and organic acids. Especially, higher levels of ABA, proline, arginine, lysine, aromatic and branched chain amino acids, GABA, saccharopine, 2-aminoadipate, and allantoin were found in DT under stress condition. Combination of transcriptomic and metabolomic analysis highlights the important role of amino acid metabolism (especially saccharopine pathway) and ABA metabolism and signaling pathway for drought tolerance in sesame.
The results of the present study provide valuable information for better understanding the molecular mechanism underlying drought tolerance of sesame, and also provide useful clues for the genetic improvement of drought tolerance in sesame.
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•Waste disposal and its hazardous impact on health and the environment.•Latest technologies for converting the organic waste to multiple biofuels production.•Organic acids, ...bioplastic, and bio-compost production from organic waste.•Described the techno-economic analysis for organic waste.
Rapid population growth and other human activities have generated massive waste from various sectors in recent decades. Studies revealed that by 2050, global solid waste generation is expected to reach 70% to 3.4 billion metric tons. Thus, the authorities urgently need to provide a low-cost, efficient technology for treating waste disposal. However, it is evident that only 20% of waste is recycled, and the remaining is still being considered for landfilling. In developing countries, the generated waste is simply disposed of in an open area, which causes a severe threat to humans, animals, and the environment. To date, organic waste and fourth-generation biomass have been investigated for multiple targeted products. Thus, the present review article highlights the emerging problems in organic waste generation, management, and converting them into various value-added bioproducts. This review also deals with the conversion of multiple biofuels such as liquid, solid, gaseous, and bioelectricity from organic waste resources. Besides, the latest approaches in organic waste are also detailly addressed for the production of value-added bioproducts such as bioplastic, bio-compost, and organic acids. Furthermore, the techno-economic analysis (TEA) and life cycle assessment (LCA) of organic waste is also explored. The transformation of organic waste to value-added bioproducts enhances the circular bioeconomy approach by reducing waste, increasing energy production, and other healthcare products. Finally, it is concluded that the utilization of organic waste to value-added bioproducts and biofuels production will be helpful in achieving high energy security, environmental protection, as well as enhancing the bioeconomy perspective.
High levels of carbonaceous aerosol exist over South Asia, the area adjacent to the Himalayas and Tibetan Plateau. Little is known about if they can be transported across the Himalayas, and as far ...inland as the Tibetan Plateau. As important constituents of aerosols, organic acids have been recognized as unique fingerprints to identify the atmospheric process. Here we measured dicarboxylic acids and related compounds in aerosols on the northern slope of Mt. Everest (Qomolangma, 4276 m a.s.l.). Strong positive correlations were observed for dicarboxylic acids with biomass burning tracers, levoglucosan and K(+), demonstrating that this area was evidently affected by biomass burning. The seasonal variation pattern of dicarboxylic acids is consistent with OC and EC, being characterized by a pronounced maximum in the pre-monsoon season. Molecular distributions of dicarboxylic acids and related compounds (malonic acid/succinic acid, maleic acid/fumaric acid) further support this finding. We suggest that the local meteorological conditions and regional atmospheric flow process could facilitate the penetration of the carbonaceous aerosols from South Asia throughout the Himalayas. With the consideration of the darkening force of carbonaceous aerosols, our finding has important implication for this climate-sensitive area, where the glacier melting supplies water for billions of people downstream.
Chlorine dioxide (ClO2) is commonly generated by mixing sodium chlorite and acid. This study aimed to evaluate how acid affects the release kinetics and antimicrobial property of ClO2. Solutions made ...with weak acids released ClO2 more slowly and had higher stability than those made with hydrochloric acid. Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes were treated with 1, 2.5, and 5 ppm ClO2 for 3 or 5 min. Lettuce inoculated with the pathogenic bacteria were treated with 2.5 and 5 ppm ClO2 for 5 min. The effects of peptone load at 0.01% and 0.02% on the antimicrobial efficacy of ClO2 were investigated in S. Typhimurium cell suspensions. The contribution of acids alone at the pH of the ClO2 solutions to bacterial reduction was also evaluated. The 2.5 ppm ClO2 solutions made with citric acid, lactic acid, and malic acid showed higher reductions in all three bacteria than ClO2 made with hydrochloric acid and sodium bisulfate. The 5 ppm ClO2 solutions produced with organic acids reduced populations of all bacterial strains from 7 log CFU/mL to undetectable level in 3 min, except S. Typhimurium treated by ClO2 produced with lactic acid. On inoculated Romaine lettuce model, 5 ppm ClO2 produced with lactic acid and malic acid resulted in the highest reduction of E. coli O157:H7, S. Typhimurium, and L. monocytogenes of approximately 1.4, 1.7, and 2.4 log CFU/g, respectively. The antimicrobial efficacy of ClO2 made with HCl and NaHSO4 were affected by 0.01% and 0.02% peptone load, respectively. Food-grade organic acids produced aqueous ClO2 solutions with stronger antimicrobial properties than inorganic acids. The acids alone at the pH of ClO2 did not show significant bacterial reductions.
•Organic acids produce ClO2 with stronger antimicrobial properties than inorganic acids.•Organic acids produce ClO2 less affected by peptone load than inorganic acids.
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