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Oxalic acid, one of the common organic acids secreted by microorganisms, was used to modify the biochar of sludge (SB) and rice husk (RB), and the adsorption function of biochar was combined with the reductive property of oxalic acid to repair Cr(VI). The biochar materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform attenuated total reflection infrared spectroscopy (ATR-IR), and the mechanism of chromium hexavalent removal was studied. Adsorption experiments showed that the removal rate of Cr(VI) with the modified SB and RB was 1.68 and 2.19 mg/g within 4h, which was 7.4 and 33 times of that before modification. Oxalic acid modification can enhance the repair of Cr(VI) by biochar in three aspects: 1. increases the BET surface area (109.34-174.13%) and decrease the average pore width (86.3-93.7%) of biochar, which increases the adsorption sites. 2. the addition of reducing oxygen-containing functional groups improves biocahr reduction performance. 3. improve reduced and unreduced Cr ion forms stable minerals on the surface of biochar. Therefore, oxalic acid can not only improve the adsorption and reduction of Cr(VI) by biochar, but also further improve the fixation/passivation of Cr ion after reduction and reduce the migration of Cr ion

Food allergy (FA) is a global public health issue with growing prevalence. Increasing evidence supports the strong correlation between intestinal microbiota dysbiosis and food allergies. Probiotic intervention as a microbiota-based therapy could alleviate FA effectively. In addition to improving the intestinal microbiota disturbance and affecting microbial metabolites to regulate immune system, immune responses induced by the recognition of pattern recognition receptors to probiotic components may also be one of the mechanisms of probiotics protecting against FA. In this review, it is highlighted in detail about the regulatory effects on the immune system and anti-allergic potential of probiotic components including the flagellin, pili, peptidoglycan, lipoteichoic acid, exopolysaccharides, surface (S)-layer proteins and DNA. Probiotic components could enhance the function of intestinal epithelial barrier as well as regulate the balance of cytokines and T helper (Th) 1/Th2/regulatory T cell (Treg) responses. These evidences suggest that probiotic components could be used as nutritional or therapeutic agents for maintaining immune homeostasis to prevent FA, which will contribute to providing new insights into the resolution of FA and better guidance for the development of probiotic products. [ABSTRACT FROM AUTHOR]

Microorganisms have difficulty surviving and performing remediation functions in mixed systems with high concentrations of Pb and Cd. Biochar has the potential to assist microorganism remediation as an excellent adsorbent for heavy metals. In this study, pig manure biochar (PMB) was used to assist phosphorus solubilizing bacteria (PSB) to explore the mineralization protection and biofeedback mechanism of biochar on PSB under mixed stress of 1000 mg/L Pb2+ and 500 mg/L Cd2+. The adsorption results showed that the removal of Pb2+ and Cd2+ by PMB+PSB was 148.77% and 72.27% higher than that by PSB. Meanwhile, the non-bioavailable fraction of Cd2+ and acid-soluble fraction of Pb2+ in PMB+PSB were increased by 9% and 3%, respectively. Mineralogical and microbial secretion results confirm that showed that the acidic soluble fraction and non-bioavailable fraction were mostly Pb/Cd-carbonate and Pb/Cd-phosphate. The pore adsorption and precipitation (carbonate) of biochar were able to reduce the exposure of PSB to Pb/Cd and the background stress concentration, thus stimulating the biological positive feedback effect of PSB and forming a microenvironment in the cell periphery. The vesicle detoxification and extracellular polymeric substance protection mechanism of PSB were improved under biochar protection, and the individual size and activity of PSB cells were enhanced. Besides, citric acid release from PSB (28.85% increase) accelerated the dissolution of unstable Cd-carbonate, thereby releasing a large amount of Cd2+ to compete with Pb2+ for PO 4 3-. Thus, the protection of biochar and the positive feedback effect of PSB could reduce the biotoxicity of Cd2+ in the stress system by preferentially forming a stable Cd-phosphate. In addition, the excellent electrical conductivity and organic material adsorption of biochar increased the extracellular electron transport rate of microorganisms, which further accelerated the mineralization and immobilization of Pb2+ and Cd2+, so as to ensure the repair effect of PSB on heavy metals. [Display omitted] • Biochar and phosphorus-dissolving bacteria were used to repair PB/Cd mixed pollution. • Biochar stimulated the biological positive feedback effect of PSB. • Organic acid secretion is key to the transformation of heavy metals by PSB. • The CO32- of biochar is the basis for enhanced PSB remediation of mixed Pb/Cd. • The mechanism of Pb/Cd simultaneous immobilization by PSB on biochar was deduced. [ABSTRACT FROM AUTHOR]

Particle size, one of the predominant factors that affect the adsorption capacity of biochar, has been widely investigated. However, correlative studies on a coexistence system containing various ions together with differentiated particle sizes are scarce. In this study, samples of municipal solid waste (sludge) biochar (SB) with different particle sizes were separated and examined for the adsorption performance in bi-cation (Pb 2+ /Zn 2+ ) and multi-ion (Pb 2+ , Zn 2+ and Cl - ) systems. The results showed that the adsorption capacity is influenced by both particle size and ion configurations. The effective stabilization ability of a small size group can be attributed to the most non-bioavailable fraction. Meanwhile, the acidic soluble and non-bioavailable fraction of Pb 2+ /Zn 2+ reached more than 90%. The mixed adsorption experiment showed that Pb 2+ would compete for the adsorption sites of biochar with Zn 2+ , and Cl - intervention could improve the adsorption of Pb 2+ (2.33-6.93%) and Zn 2+ (16.52-18.01%) on biochar. Further, X-ray diffraction spectra and phosphorus concentration dynamics and kinetics simulations revealed that more abundant active sites in the formatted pyromorphite were able to be exposed in the presence of Cl - . The small-size portion of SB therefore exhibited excellent potential for the long-term heavy metal remediation under practical conditions of multi-ion systems in an actual environment., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)