Non-specific degradation of chloroacetanilide herbicides by glucose oxidase supported Bio-Fenton reaction

Optimization of H2O2 Production in Biological Systems for Design of Bio-Fenton Reactors

The treatment of antibiotic wastewater, which is known for its micro-toxicity, inhibition, and poor biochemistry, poses significant challenges, including complex processes, high energy demands, and secondary pollution. Bio-Fenton, a novel Fenton technology, enables the in situ production of H2O2 at near-neutral pH, having low energy requirements and sustainable properties, and reduces the hazards of H2O2 transportation and storage. We preliminary self-designed a heterogeneous Bio-Fenton reactor. An aerobic SBBR system with pure algae, pure bacteria, and bacteria-algae symbiosis was first constructed to investigate the optimal process conditions through the effects of carbon source concentration, light duration, bamboo charcoal filling rate, and dissolved oxygen (DO) content on the H2O2 production and COD removal. Second, the reactor was constructed by adding iron-carrying catalysts to remove ROX and SDZ wastewater. The results demonstrated that the optimal operating parameters of aerobic SBBR were an influent carbon source concentration of 500 mg/L, a water temperature of 20 ± 2 °C, pH = 7.5, a dissolved oxygen content of 5 mg/L, a light-dark ratio of 12 h:12 h, a light intensity of 2500 Lux, an HRT of 10 h, and a bamboo charcoal filling rate of 33%. Given these conditions, the bacterial-algal system was comprehensively found to be the most suitable biosystem for this experiment. Ultimately, the dynamically coupled Bio-Fenton process succeeded in the preliminary removal of 41.32% and 42.22% of the ROX and SDZ from wastewater, respectively.

Magnetite-driven Bio-Fenton degradation of chloroacetanilide herbicides by a newly isolated hydrogen peroxide producing bacterium Desemzia sp. strain C1

The efficiency of the Fenton reaction is markedly contingent upon the operational pH related to iron solubility. Therefore, a heterogeneous Fenton reaction has been developed to function at neutral pH. In the present study, the Bio-Fenton reaction was carried out using magnetite (Fe(II)Fe(III)2O4) and H2O2 generated by a newly isolated H2O2-producing bacterium, Desemzia sp. strain C1 at pH 6.8 to degrade chloroacetanilide herbicides. The optimal conditions for an efficient Bio-Fenton reaction were 10 mM of lactate, 0.5% (w/v) of magnetite, and resting-cells (O.D.600 = 1) of strain C1. During the Bio-Fenton reaction, 1.8-2.0 mM of H2O2 was generated by strain C1 and promptly consumed by the Fenton reaction with magnetite, maintaining stable pH conditions. Approximately, 40-50% of the herbicides underwent oxidation through non-specific reactions of •OH, leading to dealkylation, dechlorination, and hydroxylation via hydrogen atom abstraction. These findings will contribute to advancing the Bio-Fenton system for non-specific oxidative degradation of diverse organic pollutants under in-situ environmental conditions with bacteria producing high amount of H2O2 and magnetite under a neutral pH condition.

Targeted Detoxification of Aflatoxin B1 in Edible Oil by an Enzyme-Metal Nanoreactor

Mycotoxin contamination is an important issue for food safety and the environment. Removing mycotoxins from food without losing nutrients and flavor components remains a challenge. In this study, a novel strategy was proposed for the targeted removal of aflatoxin B1 (AFB1) from peanut oil using an amphipathic enzyme-metal hybrid nanoreactor (PL-GOx-Fe3O4@COF) constructed with covalent organic frameworks (COFs) which can selectively adsorb AFB1. Due to the confined space provided by COFs and the proximity effect between GOx and Fe3O4, the detoxification of AFB1 is limited in the nanoreactor without affecting the composition and properties of the oil. The detoxification efficiency of AFB1 in the chemoenzymatic cascade reaction catalyzed by PL-GOx-Fe3O4@COF is six times higher than that of the combination of free GOx and Fe3O4. The AFB1 transformation product has nontoxicity to kidney and liver cells. This study provides a powerful tool for the targeted removal of mycotoxins from edible oils.

Understanding atrazine elimination via treatment of the enzyme-based Fenton reaction: Kinetics, mechanism, reaction pathway, and metabolites toxicity

The degradation kinetics and mechanism of atrazine (ATZ) via an enzyme-based Fenton reaction were investigated at various substrate concentrations and pH values. Toxicological assessment was conducted on ATZ and its degradation products, and the associated reaction pathway was examined. The in situ production of hydrogen peroxide (H2O2) was monitored within the range of 3-15 mM, depending on the increase in glucose concentration, while decreasing the pH to 3.2-5.1 (initial pH of 5.8) or 6.5-7.4 (initial pH of 7.7). The degradation efficiency of ATZ was approximately 2-3 times higher at an initial pH of 5.8 with lower glucose concentrations than at an initial pH of 7.7 with higher substrate concentrations during the enzyme-based Fenton reaction. The apparent pseudo-first-order rate constant for H2O2 decomposition under various conditions in the presence of ferric citrate was 1.9-6.3 × 10-5 s-1. The •OH concentration ([•OH]ss) during the enzyme-based Fenton reaction was 0.5-4.1 × 10-14 M, and the second-order rate constant for ATZ degradation was 1.5-3.3 × 109 M-1 s-1. ATZ intrinsically hinders the growth and development of Arabidopsis thaliana, and its inhibitory effect is marginal, depending on the reaction time of the enzyme-based Fenton process. The ATZ transformation during this process occurs through dealkylation, hydroxylation, and dechlorination via •OH-mediated reactions. The degradation kinetics, mechanism, and toxicological assessment in the present study could contribute to the development and application of enzyme-based Fenton reactions for in situ pollutant abatement. Moreover, the enzyme-based Fenton reaction could be an environmentally benign and applicable approach for eliminating persistent organic matter, such as herbicides, using diverse H2O2-producing microbes and ubiquitous ferric iron with organic complexes.

Cost-effective, scalable production of glucose oxidase using Casuarina equisetifolia biomass and its application in the bio-Fenton oxidation process for the removal of trace organic contaminants from wastewater

This study focuses on using Casuarina equisetifolia biomass for pilot-scale glucose oxidase production from Aspergillus niger and its application in the removal of trace organic contaminants (TrOCs) from municipal wastewater through the bio-Fenton oxidation. The cost of glucose oxidase was 0.005 $/U, including the optimum production parameters, 10% biomass, 7% sucrose, 1% peptone, and 3% CaCO₃ at 96 h with an enzyme activity of 670 U/mL. Optimized conditions for H₂O₂ were 1 M glucose, 100 U/mL glucose oxidase, and 120 mins of incubation, resulting in 544.3 mg/L H₂O₂. Thus, H₂O₂ produced under these conditions lead to bio-Fenton oxidation resulting in the removal of 36-92% of nine TrOCs in municipal wastewater at pH 7.0 in 360 mins. Therefore, this work establishes the cost-effective glucose oxidase-producing H₂O₂ as an attractive bioremediating agent to enhance the removal of TrOCs in wastewater at neutral pH.

Co-Immobilization of Enzymes and Metals on the Covalent-Organic Framework for the Efficient Removal of Mycotoxins

Mycotoxin is an important contaminant in food and the environment. The conventional methods for detoxification of mycotoxins are plagued by high chemical consumption, secondary pollution, and specific equipment required. In this study, we propose a chemoenzymatic cascade reaction for mycotoxin removal in an effective and green manner using an enzyme-metal hybrid catalyst synthesized by compartmental co-immobilized glucose oxidase (GOx) and Fe₃O₄ nanoparticles (NPs) on a flower-shaped covalent organic framework (COF). The GOx-Fe₃O₄@COF hybrid catalyst exhibits excellent activity in mycotoxin removal due to the enrichment of mycotoxins in COF and the cooperative catalysis between GOx and Fe₃O₄ NPs. The degradation efficiency of aflatoxin B₁ (AFB₁) in the chemoenzymatic cascade reaction catalyzed by GOx-Fe₃O₄@COF is 3.5 times higher than that in the Fenton reaction catalyzed by Fe₃O₄@COF. The GOx-Fe₃O₄@COF hybrid catalyst is highly active in a wide pH range of 3.0-7.0, overcoming the limitation of the Fenton reaction that can only perform below pH 3.0. This study provides a powerful tool for the efficient removal of mycotoxins.

Bio-Fenton-Assisted Biological Process for Efficient Mineralization of Polycyclic Aromatic Hydrocarbons from the Environment

The intensive production of fossil fuels has led to serious polycyclic aromatic hydrocarbon (PAH) contamination in water and soil environments (as PAHs are typical types of emerging contaminants). Bio-Fenton, an alternative to Fenton oxidation, which generates hydrogen peroxide at a nearly neutral pH condition, could ideally work as a pretreatment to recalcitrant organics, which could be combined with the subsequent biological treatment without any need for pH adjustment. The present study investigated the performance of a Bio-Fenton-assisted biological process for mineralization of three typical types of PAHs. The hydrogen peroxide production, PAH removal, overall organic mineralization, and microbial community structure were comprehensively studied. The results showed that the combined process could achieve efficient chemical oxygen demand (COD) removal (88.1%) of mixed PAHs as compared to activated sludge (33.1%), where individual PAH removal efficiencies of 99.6%, 83.8%, and 91.3% were observed for naphthalene (NAP), anthracene (ANT), and pyrene (PYR), respectively, with the combined process.