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Anaerobic digestion of livestock and poultry waste has been confined to the low efficiency and the accumulation of harmful heavy metals. An effective way can be expected for the nanomaterials or biochar-based materials rich in the trace element selenium (Se). Particularly, selenium nanoparticles (SeNPs) have attracted much more interests in recent years, due to their low toxicity, high biocompatibility, and excellent physicochemical properties. Therefore, the SeNPs have been widely used in the various fields, such as environmental remediation, agricultural production, clinical medicine, and chemical manufacturing. Generally, the SeNPs can be synthesized by different approaches (e.g. biological, physical, and chemical ones). This study aims to explore the effects of hydrochar-based nano selenium on methane production and arsenic removal from mesophilic and thermophilic anaerobic digestion of swine manure. The Bacillus subtilis subspecies stercoris strain XP from our laboratory was added into the preparation of bio-nano selenium. Bio-nano selenium and garden wastes (i.e., bark, branches, and wood chips of arboreal trees) were applied to prepare the hydrochar-based nano selenium (SeHC) through hydrothermal carbonization. And then the physicochemical properties of SeHC were further analyzed to facilitate the subsequent applications. Scanning electron microscopy (SEM), mapping imaging, and energy-dispersive X-ray spectroscopy (EDX) were applied to characterize the resulting materials. Batch experiments of anaerobic digestion were carried out to verify the preparation. Swine manure containing arsenic (4.43 mg/kg) was taken as the research object. The SeHC was also added for the reinforcement. Three treatment groups were also applied, including hydrochar (HC), bio-nano selenium (Se), and SeHC. A systematic investigation was implemented to explore the effects of different treatments on methane production of swine manure and the removal rate of arsenic under mesophilic (37°C) and thermophilic (44°C) anaerobic digestions. Meanwhile, the treatment group without any addition of hydrochar or selenium was considered as the control (CK). The results showed that the SeHC shared a multi-dimensional spatial structure, where the spherical nano-selenium particles with a diameter of 100~200 nm were successfully loaded on the surface of SeHC. The BET (Brunauer-Emmett-Teller) surface area of SeHC was significantly (P<0.05) enhanced by 15.1%, compared with the HC without selenium modification. Fourier Transform Infrared Spectroscopy (FT-IR) indicated that much many more types of surface functional groups (e.g. N-H, C=O, C-O, and C-X) were found in the SeHC. Moreover, the Gompertz model fitting showed that the thermophilic fermentation coupled with SeHC treatment group was more conducive to the anaerobic methanization. In terms of the mesophilic and thermophilic anaerobic conditions, the final cumulative methane production (P’) and the maximum methane production rate (Rm) of the SeHC treatment group were significantly promoted by 39.37%, 11.70%, 72.20%, and 75.54%, respectively, compared with the CK group. Meanwhile, the treatment of SeHC shared the better efficiency in the removal of arsenic under anaerobic digestion. The removal rate was ranked in the descending order of the SeHC, Se, HC, CK. Specifically, the maximum removal rate was 5.3% and 10.7% in the mesophilic and thermophilic digestion, respectively. In summary, the SeHC coupled with the thermophilic anaerobic digestion can be expected to improve the anaerobic digestion for the rapid removal of harmful substances, such as arsenic. The findings can also provide a theoretical reference to develop the hydrochar-based nano selenium in the environmental and bioenergy production. [ABSTRACT FROM AUTHOR] more...

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) more...

Nano-selenium, as a kind of new functional nanomaterials, has attracted wide attention from all over the word. Compared with inorganic selenium, organic selenium or elemental selenium, nano-selenium has a lot of outstanding features, including high biological activity, low toxicity, and large surface area. Biosynthetic process is regarded as a relatively efficient and environment-friendly pathway to produce nanomaterials. Our previous study found that Bacillus subtilis subspecies stercoris strain XP, as a biocontrol bacteria strain, not only had strong resistance to selenium or salt, but also had strong ability of transform inorganic selenium with higher toxicity into selenium nanoparticle (SeNP) with higher bioactivity and safety. Furthermore, the strain XP has been confirmed to have higher safety and bioactivity compared to those identified strains. But so far, the SeNP yield from selenite reduction by strain XP metabolism is inefficient, which seriously hinders the wide application of this technology. As we all known, fermentation process parameters have great influence on the selenite reduction and SeNP yield. Choosing appropriate parameters can increase in the SeNP production, as well as reduce the cost of SeNP synthesis. Response surface methodology (RSM) has been considered to be an effective method of process parameter optimization. In this study, the synthesis conditions (e.g., selenite concentration, speed of cultivation, dosage of inoculation) were further optimized to improve the biological efficiency of SeNP synthesis by strain XP. The fermentation conditions were optimized by single factor test, Box-Behnken design (BBD), and response surface methodology. Firstly, the effects of different initial Se (IV) concentrations (1-8 mmol/L) in the culture medium, shaker speeds (120-200 r/min), and the amounts of strain XP inoculation (0.5-10%) on SeNP production were tested by single factor experiment. The production of SeNP increased first and then decreased with gradual increase of initial Se (IV) concentrations. With the shaking speed going up from 120 r/min to 200 r/min, SeNP production also increased first and then decreased. When the inoculum amount of strain XP was between 0.5% and 10%, the yield of SeNP enhanced rapidly along with the increase of inoculum amount. The results showed that each selected experiment parameter had a strong influence on the SeNP production within their scopes: 1-4 mmol/L Se(IV), 120-180 r/min, and 2.5%-10%, respectively. Based on it, the optimal range of each indicator was confirmed. Meanwhile, the above three factors were taken as the influencing factors and SeNP production was used as the response index. Secondly, the Box-Behnken response surface methodology (RSM) was applied to optimize the fermentation conditions of strain XP used for SeNP biosynthesis. Finally, the optimal theoretical value of fermentation condition obtained through response surface experiments were verified by actual experiments. The results indicated that the optimal fermentation condition for SeNP biosynthesis by Bacillus subtilis XP were as follows: initial Se (IV) concentration of 3.4 mmol/L, shaker speed of 157 r/min, and inoculum amount of 9.9%. The SeNP production was 1.82 mmol/L under the optimum condition, which was increased by more than 60% over that under normal condition. Moreover, the seed germination experiment was conducted for confirming the bio-activity of SeNP biosynthesis under optimized culture condition. Application of SeNP could effectively stimulate the Indian lettuce seed vigor and promote the germination process. [ABSTRACT FROM AUTHOR] more...

Copyright of Journal of Ecology & Rural Environment is the property of Journal of Ecology & Rural Environment Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) more...

Low selenium areas of China are covering about 72% of the land area. People who are seriously deficient in selenium always suffering a variety of diseases due to that they could not get enough selenium from the local food. Therefore, it is significant to solve the problems caused by the selenium deficiency in human body with scientific methods. Plant-based foods provide an indispensable source of carbohydrates and minerals for animals and human. Selenium in the environment can be absorbed and transformed into organic species by plants, which is a safe and effective way to meet the people's demand of selenium. Mineral nutrients required for plant growth almost come from the soil that is suitable for microbial survival, also, microorganism not only play an important role in promoting plant growth but also is advantageous to the plants absorbing and utilizing selenium in the soil effectively. In this paper, the research progress of selenium transformation in animals, plants, and microorganism were reviewed to give people some enlightenments for further improving the present situation of selenium deficiency in animals and human. [ABSTRACT FROM AUTHOR] more...