Characterization of modified rice straw biochar in immobilizing Bacillus subtilis 168 and evaluation on its role as a novel agent for zearalenone-removal delivery

Development of multifunctional immobilized bacterial agents for multi-pesticides degradation and environment remediation

The proliferation of weeds, pests, and plant diseases in crop cultivation has driven the increased application of herbicide lactofen, insecticide acetamiprid, and fungicide carbendazim, contributing to environmental pollution. Microorganisms are requently employed to remove pesticide residues from the environment. However, Liquid bacterial agents encounter difficulties in transportation and preservation during application and the current immobilized bacterial agents have a single degradation function. This study developed immobilized bacterial agents containing the lactofen-degrading strain Bacillus sp. Za, the acetamiprid-degrading strain Pigmentiphaga sp. D-2, and the carbendazim-degrading strain Rhodococcus sp. djl-6. Preparation conditions, including activated carbon concentration, sodium alginate (SA), CaCl2, and immobilization time, were optimized using the response surface method (RSM). The degradation performance of the immobilized bacteria was evaluated, with degradation rates exceeding 70% for all three pesticides under conditions of 30 °C, pH 7.0, and 6% inoculation over 48 h. The immobilized bacterial agents were stored at pH 7.0 and 4 °C for 180 days, maintaining a preservation rate of 51.26% with a viable cell count of 1.04 × 108 CFU/g. These agents effectively remediated soil and water contaminated with multi-pesticides, achieving degradation rates of 92.50% and 98.50% for lactofen, 91.05% and 99.89% for acetamiprid, 88.43% and 98.99% for carbendazim within 21 in soil and 7 days in water, respectively. This study provides essential technical support for developing microbial agents capable of degrading multi-pesticides residues, with significant potential applications in agriculture and environmental protection.

Effect of lignin carbon material on phosphorus solubilisation performance of Bacillus megaterium

Secondary salinisation significantly compromises soil quality because of the over-application of chemical fertilisers. The combined application of biochar and microorganisms enhanced soil physicochemical properties and improved soil remediation efficiency. However, different types of biochar had varying effects on microbial growth and reproduction. A phosphate-solubilising bacterial agent (BM-LPC) was obtained by low-temperature carbonisation/activation lignin-based porous carbon (LPC) in situ culture/adsorption Bacillus megaterium (BM). The maximum soluble phosphorus capacity of BM-LPC was 744.29 mg/L when 1 % LPC was added. This was a 22 % increase compared with BM alone. The maximum adsorption of BM by LPC was 3.66 × 109 colony-forming units (CFU)/g. At 150 days, the viable bacterial count of BM-LPC was 2.09 × 109 CFU/g. The abundances of -OH, -COOH, -NH2, and CO groups on the surface of LPC provided a stable environment for BM, which in turn, enhanced the solubilisation of phosphorus and extended the viability of BM. The findings of this study can help increase the added value of industrial lignin and provide a theoretical basis for soil remediation research.

MgO anchored N-doping biochar enhances the bensulfuron-methyl biodegradation by Acinetobacter YH0317: Higher reactive oxygen species level and bacterial viability

Bensulfuron-methyl (BSM) is a typical broad-spectrum sulfonylurea herbicide and the runoff of BSM residues from agricultural regions poses a significant threat to the ecosystem. Here we develop a bacteria-material hybrid system constructed by Acinetobacter YH0317 and Mg(NO3)2 modified biochar (MBC) for efficiently degrading BSM under various conditions including pH and temperature. Results showed that BSM biodegradation efficiency by YH0317&MBC (96.7 %) was significantly higher than YH0317&BC (79.5 %) and YH0317 (43.9 %) at 15 °C after 7 d of incubation. The addition of MBC significantly increased the reactive oxygen species (ROS) level, which was significantly higher than group YH0317. Moreover, the bacterial viability, extracellular polymeric substances (EPS) production, and membrane permeability of YH0317 were also enhanced with the addition of MBC. The electron paramagnetic resonance (EPR) and quenching experiments revealed that singlet oxygen (1O2) was the dominant active substance produced by MBC. The YH0317&MBC could effectively remove the BSM, and reduce the oxidative stress to soybean, which was beneficial to the growth of soybean through hydroponic experiment. This study establishes a microorganism-material system that efficiently removes BSM in aquatic environments and emphasizes the importance of ROS in pollution removal by the hybrid system.

Integrated remediation and detoxification of triclocarban-contaminated water using waste-derived biochar-immobilized cells by long-term column experiments

Triclocarban (TCC), an antibacterial agent commonly used in personal care products, is one of the top ten contaminants of emerging concern in various environmental media, including soil and contaminated water in vadose zone. This study aimed to investigate TCC-contaminated water remediation using biochar-immobilized bacterial cells. Pseudomonas fluorescens strain MC46 (MC46), an efficient TCC-degrading isolate, was chosen, whereas agro-industrial carbonized waste as biochar was directly used as a sustainable cell immobilization carrier. According to the long-term TCC removal performance results (160 d), the biochar-immobilized cells consistently exhibited high TCC removal efficiencies (84-97%), whereas the free MC46 removed TCC for 76-94%. At 100 days, the detachment of the MC46 cells from the immobilized cell column was observed. The micro-Fourier-transform infrared spectroscopy results indicated that extracellular polymeric substance (EPS) was produced, but polysaccharide and protein fractions were washed out of the column. The lipid fraction of EPS adhered to the biochar, promoting TCC sorption for long-term treatment. The shortening of MC46 cells improved the tolerance of TCC toxicity. The TCC-contaminated water was successfully detoxified by the biochar-immobilized MC46 cells. Overall, the waste-derived biochar-immobilized cell system proposed in this study for the removal of emerging contaminants, including TCC, is efficient, economical, and aligned with the sustainable development concept of value-added utilization of waste.

Novel cow dung-doped sludge biochar as an efficient ozone catalyst: Synergy between graphitic structure and defects induces free radical pathways

A composite material, cow dung-doped sludge biochar (Zn@SBC-CD), was synthesized by one-step pyrolysis using ZnCl2 as an activating agent and applied to a catalytic ozonation process (COP) for methylene blue (MB) removal. SEM, XRD, FTIR, XPS and BET analyses were performed to characterize the biochar (BC) catalysts. Zn@SBC-CD had high graphitization degree, abundant active sites and uniform distribution of Zn on its surface. Complete removal of MB was achieved within 10 min, with a removal rate much higher than that of ozone alone (32.4%), implying the excellent ozone activation performance of Zn@SBC-CD. The influence of experimental parameters on MB removal efficiency was examined. Under the optimum conditions in terms of ozone dose 0.04 mg/mL, catalyst dose 400 mg/L and pH 6.0, COD was completely removed after 20 min. Electron paramagnetic resonance (EPR) analysis revealed radical and non-radical pathways were involved in MB degradation. The Zn@SBC-CD/O3 system generated superoxide anion radicals (•O2-), which were the main active species for MB removal, through adsorption, transformation, and transfer, Furthermore, Zn@SBC-CD exhibited good reusability and stability in cycling experiments. This study provides a novel approach for the utilization of cow dung and sludge in synthesis of functional biocatalysts and application in organic wastewater treatment.

Simultaneous achievement of removing bensulfuron-methyl and reducing CO2 emission in paddy soil by Acinetobacter YH0317 immobilized boron-doping biochar

Herbicide residue and greenhouse gas (GHG) emission are two main problems in the paddy rice field, which have barely been considered simultaneously. Herein, a bensulfuron-methyl (BSM)-degrading bacterium named Acinetobacter YH0317 was successfully immobilized on two kinds of biochars and subsequently applied in the paddy soil. The BSM removal rate of Acinetobacter YH0317 immobilized boron-doping biochar (BBC) was 80.42% after 30 d, which was significantly higher than that of BBC (39.05%) and Acinetobacter YH0317 (49.10%) applied alone. BBC acting as an immobilized carrier could enable Acinetobacter YH0317 to work in harsh and complex environment and thus improve the BSM removal efficiency. The addition of Acinetobacter YH0317 immobilized BBC (TP5) significantly improved the soil physicochemical properties (pH, SOC, and NH4+-N) and increased the diversity of soil microbial community compared to control group (CG). Meanwhile, Acinetobacter YH0317 immobilized BBC reduced the CO2-equivalent emission by 41.0%. Metagenomic sequencing results revealed that the decreasing CO2 emission in TP5 was correlated with carbon fixation gene (fhs), indicating that fhs gene may play an important role in reducing CO2 emission. The work presents a practical and supportive technique for the simultaneous achievement on the soil purification and GHG emission reduction in paddy soil.

Adsorption characterization of tetracycline antibiotics on alkali-functionalized rice husk biochar and its evaluation on phytotoxicity to seed germination

This work presented adsorption characteristics of tetracycline antibiotics (TCs) on KOH-functionalized rice husk biochar pyrolyzed at 700 °C (KBC700) and evaluation on phytotoxicity of TCs-adsorbed aqueous phase to seed germination. Specifically, KBC700 gained eightfold rise in specific surface area by KOH activation. Predominant monolayer chemisorption helped KBC700 control TCs, and spontaneous and exothermic features were identified by thermodynamic studies. KBC700 could efficiently work in a wide pH range (4.5 ~ 9.5), as well as in simulated eutrophic water and co-existing cationic solution. Humic acid exerted negative impact on TCs disposal. Outstanding regeneration capability and stability were also found during adsorption-desorption cycles. Mechanism discussion implied predominant pore filling and π-π interaction accompanied by hydrogen bonding and electrostatic interaction involved in TCs-removal process. Importantly, less phytotoxicity to seed germination was found in TCs-adsorbed aqueous phase. Collectively, these findings contribute to adsorption properties recognition and subsequent application for KOH-modified rice rusk biochar in environmental TCs remediation.

Biochar-assisted degradation of oxytetracycline by Achromobacter denitrificans and underlying mechanisms

Contamination of the environment with large amounts of residual oxytetracycline (OTC) and the corresponding resistance genes poses a potential threat to natural ecosystems and human health. In this study, an effective OTC-degrading strain, identified as Achromobacter denitrificans OTC-F, was isolated from activated sludge. In the degradation experiment, the degradation rates of OTC in the degradation systems with and without biochar addition were 95.01-100% and 73.72-99.66%, respectively. Biochar promotes the biodegradation of OTC, particularly under extreme environmental conditions. Toxicity evaluation experiments showed that biochar reduced biotoxicity and increased the proportion of living cells by 17.36%. Additionally, biochar increased the activity of antioxidant enzymes by 34.1-91.0%. Metabolomic analysis revealed that biochar promoted the secretion of antioxidant substances such as glutathione and tetrahydrofolate, which effectively reduced oxidative stress induced by OTC. This study revealed the mechanism at the molecular level and provided new strategies for the bioremediation of OTC in the environment.

Enhanced removal efficiency of bensulfuron-methyl by a novel boron doping biochar-based Acinetobacter YH0317 at a lower temperature

Biochar-based bacteria are regarded as an efficient strategy for remediating organic pollutants in aquatic environments. Herein, a strain named Acinetobacter YH0317 that could degrade bensulfuron-methyl (BSM) at a lower temperature (15 °C) was isolated from a paddy rice field with long-term BSM application. Then Acinetobacter YH0317 was loaded on unmodified biochar (BC) and boron doping biochar (BBC). Results showed that BBC-based YH0317 significantly enhanced the removal efficiency of BSM (71.8-99.1%) compared with BC-based YH0317 (41.9-44.0%) and YH0317 alone (18.1-20.7%) in 24 h. BBC promoted the growth of YH0317 and secretion of extracellular secretions by providing a carrier and shelter for YH0317. The electrochemical analysis suggested BBC improved the electron transfer rate, which ultimately facilitated the removal of BSM. Hydroponic experiments indicated that BBC-based YH0317 effectively improved the growth of soybean. This work reports a novel BBC-based Acinetobacter YH0317 that could effectively remediate BSM contamination in the water environment.