Physiological and ecological constraints that cause the slow growth and depleted production of crops have raised a major concern in the agriculture industry as they represent a possible threat of short food supply in the future. The key feature that regulates the stress signaling pathway is always related to the reactive oxygen species (ROS). The accumulation of ROS in plant cells would leave traces of biomarkers at the genome, proteome, and metabolome levels, which could be identified with the recent technological breakthrough coupled with improved performance of bioinformatics. This review highlights the recent breakthrough in molecular strategies (comprising transcriptomics, proteomics, and metabolomics) in identifying oxidative stress biomarkers and the arising opportunities and obstacles observed in research on biomarkers in rice. The major issue in incorporating bioinformatics to validate the biomarkers from different omic platforms for the use of rice-breeding programs is also discussed. The development of powerful techniques for identification of oxidative stress-related biomarkers and the integration of data from different disciplines shed light on the oxidative response pathways in plants.
The present study investigated adsorptive removal of toluene and ethylbenzene from the aqueous media via using biochar derived from municipal solid waste (termed "MSW-BC") in a single and binary contaminant system at 25-45 °C. The adsorption was evaluated at different pH (3-10), experimental time (up to 24 h), and initial adsorbate concentrations (10-600 μg/L) in single and binary contaminant system. A fixed-bed column experiment was also conducted using MSW-BC (0.25%) and influent concentration of toluene and ethylbenzene (4 mg/L) at 2 mL/min of flow rate. The adsorption of toluene and ethylbenzene on the MSW-BC was mildly dependent on the pH, and the peak adsorption ability (44-47 μg/g) was recorded at a baseline pH of ~8 in mono and dual contaminant system. Langmuir and Hill are the models that match the isotherm results in a single contaminant environment for both toluene (R2 of 0.97 and 0.99, respectively) and ethylbenzene (R2 of 0.99 and 0.99, respectively) adsorption. In the binary system, the isotherm models matched in the order of Langmuir > Hill > Freundlich for toluene, whereas Hill > Freundlich > Langmuir for ethylbenzene. The adsorption in the batch experiment was likely to take place via cooperative and multilayer adsorption onto MSW-BC involving hydrophobic, π- π and n- π attractions, specific interaction such as hydrogen-π and cation-π interactions, and van der Waals interactions. The thermodynamic results indicate exothermic adsorption occurred by physical attractions between toluene and ethylbenzene, and MSW-BC. The breakthrough behavior of toluene and ethylbenzene was successfully described with Yoon-Nelson and Thomas models. The data demonstrate that the low-cost adsorbent derived from the municipal solid waste can be utilized to remove toluene and ethylbenzene in landfill leachate.
The discharge of an alarming number of recalcitrant pollutants from various industrial activities presents a serious threat to environmental sustainability and ecological integrity. Bioremediation has gained immense interest around the world due to its environmentally friendly and cost-effective nature. In contrast to physical and chemical methods, the use of microbial enzymes, particularly immobilized biocatalysts, has been demonstrated as a versatile approach for the sustainable mitigation of environmental pollution. Considerable attention is now devoted to developing novel enzyme engineering approaches and state-of-the-art bioreactor design for ameliorating the overall bio-catalysis and biodegradation performance of enzymes. This review discusses the contemporary and state of the art technical and scientific progress regarding applying oxidoreductase enzyme-based biocatalytic systems to remediate a vast number of pharmaceutically active compounds from water and wastewater bodies. A comprehensive insight into enzyme immobilization, the role of mediators, bioreactors designing, and transformation products of pharmaceuticals and their associated toxicity is provided. Additional studies are necessary to elucidate enzymatic degradation mechanisms, monitor the toxicity levels of the resulting degraded metabolites and optimize the entire bio-treatment strategy for technical and economical affordability.
A study was performed to determine the effect of Conway and f/2 media on the growth of microalgae genera. Genera of Chlorella sp., Dunaliella sp., Isochrysis sp., Chaetoceros sp., Pavlova sp. and Tetraselmis sp. were isolated from the South China Sea. During the cultivation period, the density of cells were determined using Syringe Liquid Sampler Particle Measuring System (SLS-PMS) that also generated the population distribution curve based on the size of the cells. The population of the microalgae genera is thought to consist of mother and daughter generations since these microalgae genera reproduce by releasing small non-motile reproductive cells (autospores). It was found that the reproduction of Tetraselmis sp., Dunaliella sp. and Pavlova sp. could be sustained longer in f/2 Medium. Higher cell density was achieved by genus Dunaliella, Chlorella and Isochrysis in Conway Medium. Different genera of microalgae had a preference for different types of cultivation media.
This study demonstrates the use of NMR techniques coupled with chemometric analysis as a high throughput data mining method to identify and examine the efficiency of different disruption techniques tested on microalgae (Chlorella variabilis, Scenedesmus regularis and Ankistrodesmus gracilis). The yield and chemical diversity from the disruptions together with the effects of pre-oven and pre-freeze drying prior to disruption techniques were discussed. HCl extraction showed the highest recovery of oil compounds from the disrupted microalgae (up to 90%). In contrast, NMR analysis showed the highest intensity of bioactive metabolites obtained for homogenized extracts pre-treated with freeze-drying, indicating that homogenizing is a more favorable approach to recover bioactive substances from the disrupted microalgae. The results show the potential of NMR as a useful metabolic fingerprinting tool for assessing compound diversity in complex microalgae extracts.
This study focuses on the evaluation of the performance of Chlorella sp. in removing nutrient in aquaculture wastewater and its correlation with the kinetic growth of Chlorella sp. The treatment was applied with various Chlorella sp. inoculation dosage ranging from 0% to 60% (v/v) of wastewater. The optimum inoculation dosage was recorded at 30% (v/v) with effluent concentration of ammonia and orthophosphate recording at 0.012mgL(-1) and 0.647mgL(-1), respectively on Day 11. The optimum dosage for bio-flocculation process was obtained at 30mgL(-1) of Aspergillus niger with a harvesting efficiency of 97%. This type of development of phytoremediation with continuous bio-harvesting could promote the use of sustainable green technology for effective wastewater treatment.
Nitrate is required to maintain the growth and metabolism of plant and animals. Nevertheless, in excess amount such as polluted water, its concentration can be harmful to living organisms such as microalgae. Recently, studies on microalgae response towards nutrient fluctuation are usually limited to lipid accumulation for the production of biofuels, disregarding the other potential of microalgae to be used in wastewater treatments and as source of important metabolites. Our study therefore captures the need to investigate overall metabolite changes via NMR spectroscopy approach coupled with multivariate data to understand the complex molecular process under high (4X) and low (1/4X) concentrations of nitrate ([Formula: see text]). NMR spectra with the aid of chemometric analysis revealed contrasting metabolites makeup under abundance and limited nitrate treatment. By using NMR technique, 43 types of metabolites and 8 types of fatty acid chains were detected. Nevertheless, only 20 key changes were observed and 16 were down regulated in limited nitrate condition. This paper has demonstrated the feasibility of NMR-based metabolomics approach to study the physiological impact of changing environment such as pollution to the implications for growth and productivity of microalgae population.
The huge amount of agro-wastes generated due to expanding agricultural activities can potentially cause serious environmental and human health problems. Using the biorefinery concept, all parts of agricultural plants can be converted into multiple value-added bioproducts while reducing waste generation. This approach can be viewed as an effective strategy in developing and realizing a circular bioeconomy by accomplishing the dual goals of waste mitigation and energy recovery. However, the sustainability issue of biorefineries should still be thoroughly scrutinized using comprehensive resource accounting methods such as exergy-based approaches. In light of that, this study aims to conduct a detailed exergy analysis of whole-crop safflower biorefinery consisting of six units, i.e., straw handling, biomass pretreatment, bioethanol production, wastewater treatment, oil extraction, and biodiesel production. The analysis is carried out to find the major exergy sink in the developed biorefinery and discover the bottlenecks for further performance improvements. Overall, the wastewater treatment unit exhibits to be the major exergy sink, amounting to over 70% of the total thermodynamic irreversibility of the process. The biomass pretreatment and bioethanol production units account for 12.4 and 10.3% of the total thermodynamic inefficiencies of the process, respectively. The exergy rates associated with bioethanol, biodiesel, lignin, biogas, liquid digestate, seed cake, sodium sulfate, and glycerol are determined to be 5918.5, 16516.8, 10778.9, 1741.4, 6271.5, 15755.8, 3.4, and 823.5 kW, respectively. The overall exergetic efficiency of the system stands at 72.7%, demonstrating the adequacy of the developed biorefinery from the thermodynamic perspective.
Microalgae have been increasingly used to generate biofuel, thus a sustainable technique should be implemented to harvest the biomass to ensure its existence in the environment. Aspergillus niger was used as bio-flocculant to harvest microalgae from aquaculture wastewater via flocculation technique over a range of pH and mixing rate. The bio-flocculant showed ability to adapt at a wide range of pH from 3.0 to 9.0 and at a mixing rate of 100-150 rpm, producing a harvesting efficiency of higher than 90%. The treated water possessed low concentration of chlorophyll-a (0.3-0.6 mg L-1) and cell density (2 × 106-3 × 106 cell mL-1). These indicate that Aspergillus niger is a promising bio-flocculant to be used in harvesting microalgae, thus promoting the use of flocculation as a green technology in aquaculture wastewater treatment.
In an effort to seek a new technical platform for disposal of drinking water treatment sludge (DWTS: alum sludge), pyrolysis of DWTS was mainly investigated in this study. To establish a more sustainable thermolytic platform for DWTS, this study particularly employed CO2 as reactive gas medium. Thus, this study laid great emphasis on elucidating the mechanistic roles of CO2 during the thermolysis of DWTS. A series of the TGA tests of DWTS in CO2 in reference to N2 revealed no occurrence of the heterogeneous reaction between CO2 and the sample surface of DWTS. As such, at the temperature regime before initiating the Boudouard reaction (i.e., ≥700 °C), the mass decay patterns of DWTS in N2 and CO2 were nearly identical. However, the gaseous effluents from lab-scale pyrolysis of DWTS in CO2 in reference to N2 were different. In sum, the homogeneous reactions between CO2 and volatile matters (VMs) evolved from the thermolysis of DWTS led to the enhanced generation of CO. Also, CO2 suppressed dehydrogenation of VMs. Such the genuine mechanistic roles of CO2 in the thermolysis of DWTS subsequently led to the compositional modifications of the chemical species in pyrolytic oil. Furthermore, the biochar composite was obtained as byproduct of pyrolysis of DWTS. Considering that the high content of Al2O3 and Fe-species in the biochar composite imparts a strong affinity for As(V), the practical use of the biochar composite as a sorptive material for arsenic (V) was evaluated at the fundamental levels. This work reported that adsorption of As(V) onto the biochar composite followed the pseudo-second order model and the Freundlich isotherm model.
The fast pyrolysis of waste lignin derived from biobutanol production process was performed to determine the optimal pyrolysis conditions and pyrolysis product properties. Four types of pyrolysis reactors, e.g.: micro-scale pyrolyzer-gas chromatography/mass spectrometry, lab and bench scale fixed bed (FB) reactors, and bench scale rotary kiln (RK) reactor, were employed to compare the pyrolysis reaction conditions and product properties obtained from different reactors. The yields of char, oil, and gas obtained from lab scale and bench scale reactor were almost similar compared to FB reactor. RK reactor produced desirable bio-oil with much reduced yield of poly aromatic hydrocarbons (cancer precursor) due to its higher cracking reaction efficiency. In addition, char agglomeration and foaming of lignin pyrolysis were greatly restricted by using RK reactor compared to the FB reactor.
As an abundant and fast-growing biomass, bamboo can be used as construction materials owing to its desirable physical and mechanical properties, environmentally friendly features, and alternative to replace toxic and hazardous wastes in industrial processing. In this study, grid material made from bamboo (termed 'bamboo grid') was developed and compared to commercially used polyvinyl chloride (PVC) as packing material in cooling towers; PVC packing has drawbacks such as fouling, deposit buildup, low durability, and is harmful to environments. The cooling capacity, energy efficiency and environmental impact of bamboo grid packing were evaluated via life cycle assessment (LCA), particularly the cumulative energy demand (CED) and the Building for Environmental and Economic Sustainability (BEES). Although the thermal performance of the PVC packing was found higher than that of the bamboo grid packing, the bamboo grid packing showed improved resistance characteristic, recording a total saving of 529.2 tons of standard coal during a six-month field test in a real thermal power generation plant. LCA results revealed that the utilization of bamboo-grid packing to replace PVC packing in cooling towers reduced total CED from 3420 MJ to 561 MJ per functional unit, achieving 6 times reduction. A desirable reduction ranging from 1.5 to 10.5 times was also recorded for the BEES indices. This LCA comparison analysis confirmed the improvement of energy efficiency and reduction of environmental impact by using the bamboo grid to replace PVC as packing material in cooling towers. The major environmental impact (BEES) indices (e.g., the total Global warming potential, Acidification, Eutrophication and Smog) were reduced by 1.5-10.5 times via the use of bamboo grid. The results demonstrate that bamboo grid packing is a good alternative to replace existing grid packing materials such as concrete and PVC that are harmful to human health and environments.
This study focused on producing high quality and yield of biodiesel from novel non-edible seed oil of abundantly available wild Raphnus raphanistrum L. using an efficient, recyclable and eco-friendly copper modified montmorillonite (MMT) clay catalyst. The maximum biodiesel yield of 83% was obtained by base catalyzed transesterification process under optimum operating conditions of methanol to oil ratio of 15:1, reaction temperature of 150 °C, reaction time of 5 h and catalyst loading of 3.5%. The synthesized catalyst and biodiesel were characterized for their structural features and chemical compositions using various state-of-the-art techniques, including x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, Fourier transform infrared spectroscopy, nuclear magnetic resonance (1H, 13C) and gas chromatography-mass spectroscopy. The fuel properties of the biodiesel were estimated including kinematic viscosity (4.36 cSt), density (0.8312 kg/L), flash point (72 °C), acid value (0.172 mgKOH/g) and sulphur content (0.0002 wt.%). These properties were compared and found in good agreement with the International Biodiesel Standards of American (ASTM-951, 6751), European Committee (EN-14214) and China GB/T 20828 (2007). The catalyst was re-used in five consecutive transesterification reactions without losing much catalytic efficiency. Overall, non-edible Raphnus raphanistrum L.. seed oil and Cu doped MMT clay catalyst appeared to be highly active, stable, and cheap contenders for future biofuel industry. However, detailed life cycle assessment (LCA) studies of Raphnus raphanistrum L. seed oil biodiesel are highly recommended to assess the technical, ecological, social and economic challenges.