Transcriptome analysis reveals self-redox mineralization mechanism of azo dyes and novel decolorizing hydrolases in Aspergillus tabacinus LZ-M.

Bio-degradation is the most affordable method of azo dye decontamination, while its drawbacks such as aromatic amines accumulation and low degradation efficiency must be overcome. In this study, a novel mechanism of azo dye degradation by a fungus was discovered. At a concentration of 400 mg/L, the decolorization efficiency of Acid Red 73 (AR73) by Aspergillus tabacinus LZ-M was 90.28%. Metabolite analysis and transcriptome sequencing analysis revealed a self-redox process of AR73 degradation, where the electrons generated in carbon oxidation were transferred to the reduction of -C-N = and -NN. The metabolites, 2-hydroxynaphthalene and N-phenylnitrous amide were mineralized into CO2 through catechol pathway and a glycolytic process. Furthermore, the mineralization ratio of dye was computed to be 31.8% by the carbon balance and electron balance. By using comparative transcriptome, a novel decoloring enzyme Ord95 was discovered in unknown genes through gene cloning. It hydrolyzed AR73 into 2-hydroxynaphthalene and N-phenylnitrous amide, containing a glutathione S-transferase domain with three arginines as key active sites. Here the new mechanism of azo dye degradation was discovered with identification of a novel enzyme in Aspergillus tabacinus LZ-M.

Treatment of nanofiltration membrane concentrates integrated magnetic biochar pretreatment with anaerobic digestion.

nanofiltration membrane concentrate (NMC) is an emerging type of wastewater with significant environmental concerns. which can be treated efficiently by an integrated method. In this study, magnetic biochar (MBC) pretreatment integrated with anaerobic digestion (AD) (MBC + AD) was used to treat NMC. Results showed that under the optimal MBC + AD conditions, 79%, 69.4%, 52.9%, and 86.5% of COD, total nitrogen (TN), chromaticity, and light absorbing substances were reduced. For heavy metals removal, 18.3%, 70.0%, 96.4%, 43.8% and 97.5% of Cr (VI), Cd, Pb, Cu and Zn were removed, respectively. LC-MS analysis indicated that p-nitrophenol (4-NP) diethyl and phthalate (DEP) were the main organic pollutants in NMC with a removal rate of 60% and 90%. Compared with single AD, in MBC + AD samples, bacterial activity was improved, and genus DMER64 (23.2%) was dominant. The predominant archaea were Methanocorpusculum (53.3%) and Methanosarcina (25.3%), with microbial restructuring and slight methane generation. Additionally, metabolic pathway prediction revealed that both bacterial and archaeal metabolism were significantly enhanced, contributing to the central functional pathways, namely microbial activity metabolism and biodegradation metabolism. In addition, the significantly increased genera Syner-01, Vulcanibacillus, Methanocorpusculum, and Norank_c_Bathyarchaeia were significantly positively related to metabolic function. This finding demonstrated that MBC + AD enhanced contaminant removal, mainly by regulating bacterial diversity and activity. Moreover, the toxicity of NMC decreased after MBC + AD treatment. This study provides a potential biological strategy for the treatment of membrane concentrates and water recovery.

Reduction of metronidazole in municipal wastewater and protection of activated sludge system using a novel immobilized Aspergillus tabacinus LZ-M.

Metronidazole (MNZ) accumulation inhibits municipal wastewater treatment bio-systems, and an effective solution to augment anaerobic activated sludge (AAS) is required. This research discovered that Aspergillus tabacinus LZ-M could degrade 77.39% of MNZ at 5 mg/L. MNZ was metabolized into urea, and the enzymes involved in its degradation were aminotransferase, methyltransferase, monooxygenase, and CN cleavage hydrolase. The strain was immobilized in polyurethane foam and used in AAS for the treatment of MNZ-containing municipal wastewater. The results showed that, using immobilized LZ-M, MNZ was completely removed, and the degradation efficiency of wastewater's chemical oxygen demand (COD) was increased from 11.7% to 83.31%. The extracellular polymer and ROS levels indicated that MNZ's toxicity on AAS was reduced. Furthermore, bioaugmentation stabilized its microbial community, and decreased MNZ resistance genes. These observations confirm that the immobilized fungi are effective in protecting AAS against antibiotic contamination in the treatment process of municipal wastewater.

Bioaugmentation improves the anaerobic co-digestion of cadmium-containing plant residues and cow manure.

Phytoremediation causes a large quantity of phytoremediation residues rich in heavy metals (HMs). This kind of plant residue can be used as a substrate for anaerobic digestion (AD) to reduce the content of HM-containing biomass, but high concentrations of HMs will inhibit the digestion efficiency and reduce the conversion efficiency of plant residues. Bioaugmentation may be an effective method to improve the degradation efficiency and methane yield of plant residues rich in HMs. In this study, a cellulose-degrading anaerobic bacteria Paracoccus sp. Termed strain LZ-G1 was isolated from cow dung, which can degrade cellulose and simultaneously adsorb Cd2+. The Cd2+ (10 mg/L)-adsorbtion efficiency and cellulose (463.12 g/kg)-degradation rate were 65.1 % and 60.59 %, respectively. In addition, using the strain LZ-G1 bioaugmented Cd2+-containing plant residues and cow manure mixed AD system, the system's biogas and methane production significantly increased (98.97 % and 142.03 %, respectively). During the AD process, the strain LZ-G1 was successfully colonized in the digestion system. Furthermore, the microbial community analysis revealed that LZ-G1 bioaugmentation alleviates the toxicity of free Cd2+ to the microbial community in the AD system, regulates and restores the archaea genus dominant in the methanogenesis stage, and restores the relative abundance of dominant bacteria associated with biomass hydrolysis. The restoration of the microbial community increased the biogas yield and methane production rate. Thus, bioaugmentation provides an easy and a feasible method for the actual on-site treatment of HM-rich phytoremediation residues.

Effects of sodium selenite spray on apple production, quality, and sucrose metabolism-related enzyme activity.

Selenium is an essential trace element that improves fruit quality and nutritional value. However, the effect of sodium selenite on apple quality and its relative sucrose metabolism activity remains unclear. In this study, we investigated the roles of selenite spraying, in improving Fuji apple quality and sucrose metabolism-related enzyme activity. Results showed that foliar spraying of sodium selenite significantly (P < 0.05) increased apple fruit yield and internal quality, but no significant effects on external quality. The apple yield, vitamin C content, sugar-acid ratio and total soluble sugar increased 4.4% to 11.7%, 4.68% to 20.86%, 3.07% to 31.57%, and 4.53% to 18.89%, respectively. Se content is 9.5-fold compared to the control. Significant correlations were observed between neutral invertase, sucrose synthase activity and sucrose phosphate synthase enzymes, and sucrose phosphate synthase enzyme was most crucial. Spraying sodium selenite of 100-150 mg/L could be appropriate for improving Fuji apple yield and quality.

Heavy metals interact with the microbial community and affect biogas production in anaerobic digestion: A review.

Heavy metals (HMs), which accumulate in digestion substrates, such as plant residues and livestock manure, can affect biogas yields during anaerobic digestion (AD). Low concentration of Cu2+ (0-100 mg/L), Fe2+ (50-4000 mg/L), Ni2+ (0.8-50 mg/L), Cd2+ (0.1-0.3 mg/L), and Zn2+ (0-5 mg/kg) promote biogas production, while high concentrations inhibit AD. Trace amounts of HMs are necessary for the activity of some enzymes. For example, Cu2+ and Cd2+ serve as cofactors in the catalytic center of cellulase and stimulate enzyme activity. High contents of Cd2+ and Cu2+ inhibit enzyme activity by disrupting protein structures. Trace amounts of HMs stimulate the growth and activity of methanogens, while high levels have toxic effects on methanogens. HMs affect the hydrolysis, acidification, and other biochemical reactions of organics in AD by changing the enzyme structure and they also impact methanogen growth. A better understanding of the impact of HMs on AD can provide valuable insights for improving the digestion of poultry manure and plant residues contaminated with HMs, as well as help mitigate HMs pollution. Although several studies have been conducted in this field, few comprehensive reviews have examined the effect of many common HMs on AD. This review summarizes the effects of HMs on the biogas production efficiency of AD and also discusses the effects of HMs on the activities of enzymes and microbial communities.

A comparative analysis of macronutrients intakes between resident and boarder-students / 中国学校卫生

Objective@#To investigate the differences in the intake of macronutrients between boarders and resident students in China, and to provide a scientific reference for relevant policies and preventive measures.@*Methods@#The difference of macronutrients level between boarders and resident students were analyzed with the multilevel model (MLM) by using the data from Chinese Health and Nutrition Survey and the indicators of Chinese Dietary Reference Intakes (DRIs) 2013.@*Results@#The daily intake of energy, carbohydrate, fat and protein were (1 597.59±557.15)kcal, (216.2±84.66)g, (57.88±31.96)g, (52.69±21.2)g respectively, with a rate of meeting DRIs of 17.32%, 84.17%, 50.30% for energy, carbohydrate and protein. There were significant differences in amount of energy, carbohydrate between boarders and resident students, but no significant difference in rate of meeting DRIs (15.09%, 87.28%, 17.54%, 83.86%, P>0.05 ). No difference in the amount of fat and protein intake between boarders and resident students, but the protein rate of meeting DRIs among resident students was significantly lower than that in boarders(34.91% vs 51.82%, χ2=4.45, P<0.01).@*Conclusion@#The results revealed an imbalanced intake of macronutrients among primary and secondary school students, which highlight the insufficiency in energy intake and the worse meeting rate of DRIs for protein among resident-student. The nutritional education targeting at boarder-students should be strengthened.

Process performance and methane production optimizing of anaerobic co-digestion of swine manure and corn straw.

During anaerobic digestion (AD) process, process parameters e.g., VFA, pH, COD removal … and kinetic parameters e.g., hydrolysis rate, lag phase and methane production potential… are the important indicator for illustrating AD process performance, however, the AD process performance based on these parameters remains poorly understood. To estimate process performance focusing on initial pH and substrate composition, the effects of initial pH and swine manure to corn straw ratio on biogas production and these parameters and linkages of these parameters were analyzed. Also, the methane production was optimized. The results revealed that the maximum methane yield and methane production rate were obtained with initial pH 7.5 and SM/CS ratio of 70:30. Kinetic parameters are coupled with process parameters, especially for COD removal rate, VS degradation rate, VFA and pH. Hydrolysis constant positively correlated with pH, COD removal rate and VS degradation rate, then impacted methane production and lag phase. Meanwhile, lag phase and the maximum methane production rate were directly determined by VFA and COD removal rate. The optimum initial pH and SM/CS ratio were 7.15 and 0.62, respectively, with a predicted maximum methane content of 55.12%. Thinking these findings together, they provide a scientific theory for estimating AD performance.

Effect of magnetite powder on anaerobic co-digestion of pig manure and wheat straw.

This study investigated the effects of different amounts of magnetite powder (i.e., 0g, 1.5g, 3g, 4.5g, 6g) on the anaerobic co-digestion of pig manure (PM) and wheat straw (WS). The variations in pH, alkalinity, cellulase activity (CEA), dehydrogenase activity (DHA) and methane production, were analyzed by phases. Correlation of the activities of the two enzymes with methane production was also analyzed, and the Gompertz model was used to evaluate the efficiency of anaerobic digestion (AD) with the addition of magnetite powder. The results showed that magnetite powder had significant effects on the anaerobic co-digestion of PM and WS. The maximum total methane production with the addition of 3g of magnetite powder was 195mL/g total solids (TS), an increase of 72.1%. The CEA and DHA increased with magnetite powder in the ranges of 1.5-4.5g, 1.5-6g, respectively, while the methane production showed a better correlation with DHA than with CEA. Using the Gompertz model, the efficiency of AD was optimal when adding 3g magnetite powder, with higher methane production potential (206mL/g TS), shorter lag-phase time (14.9d) and shorter AD period (44d).

Current status and future potential of energy derived from Chinese agricultural land: a review.

Energy crisis is receiving attention with regard to the global economy and environmental sustainable development. Developing new energy resources to optimize the energy supply structure has become an important measure to prevent energy shortage as well as achieving energy conservation and emission reduction in China. This study proposed the concept of energy agriculture and constructed an energy agricultural technical support system based on the analysis of energy supply and demand and China's foreign dependence on energy resources, combined with the function of agriculture in the energy field. Manufacturing technology equipment and agricultural and forestry energy, including crop or forestry plants and animal feces, were used in the system. The current status and future potential of China's marginal land resources, energy crop germplasm resources, and agricultural and forestry waste energy-oriented resources were analyzed. Developing the function of traditional agriculture in food production may promote China's social, economic, and environmental sustainable development and achieve energy saving and emission reduction.

Influence of initial pH on thermophilic anaerobic co-digestion of swine manure and maize stalk.

The contradictions between the increasing energy demand and decreasing fossil fuels are making the use of renewable energy the key to the sustainable development of energy in the future. Biogas, a renewable clean energy, can be obtained by the anaerobic fermentation of manure waste and agricultural straw. This study examined the initial pH value had obvious effect on methane production and the process in the thermophilic anaerobic co-digestion. Five different initial pH levels with three different manure ratios were tested. All digesters in different initial pH showed a diverse methane production after 35 days. The VFA/alkalinity ratio of the optimum reaction condition for methanogens activity was in the range of 0.1-0.3 and the optimal condition that at the 70% dung ratio and initial pH 6.81, was expected to achieve maximum total biogas production (146.32 mL/g VS).

Environmental Kuznets curve analysis of the economic development and nonpoint source pollution in the Ningxia Yellow River irrigation districts in China.

This study applies the environmental Kuznets curve to test the relationship between the regional economic growth and the different types of agricultural nonpoint source pollution loads in the Ningxia Yellow River irrigation area by using the Johnes export coefficient method. Results show that the pollution load generated by crop cultivation and livestock-breeding industries in the Ningxia Yellow River irrigation area shows an inverted U-shaped feature; however, this feature is absent in living-sewage pollution load. Crop pollution has shown a decreasing trend since 1997 because of the increased per capita income of farmers. Livestock-breeding pollution load reached its turning point when the per capita income of farmers reached 8386.74 RMB. Therefore, an increase in the per capita income of farmers corresponds to an increase in the livestock-breeding pollution load in the Ningxia Yellow River irrigation area.