A dual bacterial alliance removed erythromycin residues by immobilizing on activated carbon

Mechanistic insight into enhancement of undissolved rice husk biochar on Tetracycline biodegradation by strain Serratia marcescens basing on electron transfer response

Undissolved biochar (UBC) plays a key role in persistently affecting bacterial characteristics after loss of dissolved biochar. However, its potential role as electron shuttle mediating tetracycline (TC) removal by bacteria is less understood. Result demonstrated UBC (700°C) coupled strain MSM2304 resulted in 72.19 % of TC biodegradation (37.76 % in free cells). UBC improved nutrients usage of TOC and TN to enhance cells proliferation, and facilitated biofilms formation and secretion of redox-active-related extracellular polymeric substances (EPS) including protein (40 % higher) and humus (30 % higher). Moreover, UBC optimized cells oxidative stress indicators including reactive oxygen species (40 % lower), total antioxidant capacity (30 % higher), superoxide dismutase (35 % higher), and catalase (30 % higher) during TC exposure. Importantly, UBC not only accelerated electron transfer from intracellular into extracellular by stimulating cytochrome C reductase activity and cytochrome C development, also decreased extracellular electron transfer resistance between MSM2304 and TC from 231.7 to 109.5 Ω, proved by cyclic voltammetry and electrochemical impedance spectra of EPS, and helped quinone moieties formation on UBC through CO and CC or CO production determined by FTIR and XPS. These findings indicate UBC could be as electron shuttle and contribute to provide a better understanding of interactions between biochar and microorganism.

Characterization of modified rape straw biochar in immobilizing Aspergillus sydowii W1 pellets and evaluation on its role as a novel composite for di(2-ethylhexyl) phthalate degradation

Di(2-ethylhexyl) phthalate (DEHP) is one of the most widely used plasticizers, which has harmful biological effects and poses a serious threat to ecological environments and human health. In this study, a novel strain Aspergillus sydowii W1 was reported with DEHP degradation ability. Under the optimal conditions of 35°C and pH 6.0, strain W1 degraded 68.48 % of 50 mg/L DEHP within 120 h, while the biochar immobilized W1 can enhance the removal efficiency by 15.33 %. The immobilized W1 also showed excellent performance in DEHP polluted wastewater with concentration of 50 mg/L, and its removal rate reached 85.72 % within 144 h. Interestingly, the fermented broth of strain W1 has the activity of hydrolyzing DEHP, and the highest value of crude enzyme activity was at 35°C and pH 8.5. In addition, nine metabolic products of DEHP degraded by strain W1 were identified by HPLC-MS/MS and GC-MS. In combination with these intermediates and related enzymatic analysis, two possible catabolism pathways of DEHP degradation by strain W1 were concluded. This study confirmed that immobilized W1 is an effective composite for removing DEHP in water environment and also strengthened our understanding on the DEHP degradation process of A. sydowii.

Effects of compound immobilized bacteria on remediation and bacterial community of PAHs-contaminated soil

Immobilized microorganism technology is expected to enhance microbial activity and stability and is considered an effective technique for removing soil polycyclic aromatic hydrocarbons (PAHs). However, there are limited high-efficiency and stable bacterial preparations available. In this study, alkali-modified biochar (Na@CBC700) was used as the adsorption carrier, sodium alginate (SA) and polyvinyl alcohol (PVA) as embedding agents, and CaCl2 as the cross-linking agent to prepare immobilized Acinetobacter (CoIMB) through a composite immobilization method. The CoIMB preparation was optimized using response surface methodology and applied to PAH-contaminated soil remediation. Results indicated that CoIMB exhibited improved mechanical strength and microbial activity, achieving degradation rates of 2-5 rings PAHs up to 82.41 %, averaging 1.5 times higher than CK. High dose CoIMB treatment enhanced soil microbial community diversity, enriching Acinetobacter, and increased the abundance of functional genes related to fatty acid metabolism and energy metabolism (K00249, K01897, K00059). This composite immobilized bacterial particle provides a novel, broad-spectrum, and cost-effective solution for remediating organic pollutants in soil environments.

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.

Immobilization of Peniophora incarnata F1 in PVA-SA-biochar matrix and its degradation performance and mechanism for erythromycin degradation

Erythromycin is becoming one of the most common contaminants detected in surface water and wastewater, which poses a potential risk to ecological systems and human health. Until now, there is still no effective way to eliminate it. Herein, a novel and efficient erythromycin-degrading fungus Peniophora incarnata F1, capable of utilizing erythromycin as its sole source of carbon and energy, was isolated from contaminated sludge. Moreover, a fungal immobilization system was developed using polyvinyl alcohol (PVA), sodium alginate (SA) and rape straw biochar (RB) to enhance the removal ability of erythromycin. Under optimal conditions of 30 °C and pH 6.0, the removal rate of erythromycin with PVA-SA-RB@F1 within 5 d reached 89.90%, which is 31.43% higher than that of free strain F1 (58.47%). Furthermore, eight biodegradation products of erythromycin were identified, and five compounds were firstly reported. Based on these metabolites, we inferred erythromycin was transformed to simple products mainly by dehydration, desugar, dehydrogenation, ester bond hydrolysis and carbon chain cleavage reactions. Finally, PVA-SA-RB@F1 were applied to wastewater contained 10 mg/L and 50 mg/L erythromycin, with the removal rates of 100% and 64.97%, respectively. These results show that PVA-SA-RB@F1 can be used as an effective tool to remove erythromycin in water environment. Therefore, this study provides a feasible strategy for bioremediation of erythromycin polluted environment.

Preparation of microbial agent immobilized composites for Cr(VI) removal from wastewater

Because of its extreme toxicity and health risks, hexavalent chromium [Cr(VI)] has been identified as a major environmental contaminant. Bioreduction is considered as one of effective techniques for cleaning up Cr(VI)-contaminated sites, but the remediation efficiency needs to be enhanced. Here, a novel immobilized microbial agent was produced by immobilizing Bacillus cereus ZY-2009 with sodium alginate (SA) using polyvinyl alcohol (PVA) and activated carbon (AC). To evaluate the decrease of Cr(VI) by immobilized bacterial agents, batch tests were conducted with varying immobilization conditions, immobilization carriers, and dosages of medication. The removal of Cr(VI) by the agent prepared by the composite immobilization method was better than that by the adsorption and encapsulation methods. The optimal preparation conditions were the fraction of magnetic PVA was 5.00%, the fraction of SA was 4.00%, the fraction of CaCl2 was 4.00%, and the calcification time was 12 h. The experimental results indicated that PVA/SA/AC agents accelerated the reduction rate of Cr(VI). The removal rate of Cr(VI) by immobilized cells (90.5%) under ideal conditions was substantially higher than that of free cells (11.0%). This novel agent had a large specific surface area and a rich pore structure, accounting for its high reduction rate. The results suggest that the PVA/SA/AC immobilized Bacillus cereus ZY-2009 agent has great potential to remove Cr(VI) from wastewater treatment systems.

Study on the biodegradation characteristics and mechanism of tetracycline by Serratia entomophila TC-1

Microbial degradation is an important solution for antibiotic pollution in livestock and poultry farming wastes. This study reports the isolation and identification of the novel bacterial strain Serratia entomophila TC-1, which can degrade 87.8 % of 200 mg/L tetracycline (TC) at 35 °C, pH 6.0, and an inoculation amount of 1 % (v/v). Based on the intermediate products, a possible biological transformation pathway was proposed, including dehydration, oxidation ring opening, decarbonylation, and deamination. Using Escherichia coli and Bacillus subtilis as biological indicators, TC degraded metabolites have shown low toxicity. Whole-genome sequencing showed that the TC-1 strain contained tet (d) and tet (34), which resist TC through multiple mechanisms. In addition, upon TC exposure, TC-1 participated in catalytic and energy supply activities by regulating gene expression, thereby playing a role in TC detoxification. We found that TC-1 showed less interference with changes in the bacterial community in swine wastewater. Thus, TC-1 provided new insights into the mechanisms responsible for TC biodegradation and can be used for TC pollution treatment.

Chronic toxic effects of erythromycin and its photodegradation products on microalgae Chlorella pyrenoidosa

The photodegradation products (PDPs) of antibiotics in the aquatic environment received increasing concern, but their chronic effects on microalgae remain unclear. This study initially focused on examining the acute effects of erythromycin (ERY), then explored the chronic impacts of ERY PDPs on Chlorella pyrenoidosa. ERY of 4.0 - 32 mg/L ERY notably inhibited the cell growth and chlorophyll synthesis. The determined 96 h median effective concentration of ERY to C. pyrenoidosa was 11.78 mg/L. Higher concentrations of ERY induced more serious oxidative damage, antioxidant enzymes alleviated the oxidative stress. 6 PDPs (PDP749, PDP747, PDP719, PDP715, PDP701 and PDP557) were identified in the photodegradation process of ERY. The predicted combined toxicity of PDPs increased in the first 3 h, then decreased. Chronic exposure showed a gradual decreasing inhibition on microalgae growth and chlorophyll content. The acute effect of ERY PDPs manifested as growth stimulation, but the chronic effect manifested as growth inhibition. The malonaldehyde contents decreased with the degradation time of ERY at 7, 14 and 21 d. However, the malonaldehyde contents of ERY PDPs treatments were elevated compared to those in the control group after 21 d. Risk assessment still need to consider the potential toxicity of degradation products under long-term exposure.

Construction and application of highly efficient waste cooking oil degrading bacteria consortium in oily wastewater

The treatment of cooking oil wastewater is an urgent issue need to be solved. We aimed to screen for efficient oil-degrading bacteria and develop a new microbial agent for degrading waste cooking oil in oily wastewater. Three extremely effective oil-degrading bacteria, known as YZQ-1, YZQ-3, and YZQ-4, were found by the enrichment and acclimation of samples from various sources and separation using oil degradation plates. The 16S rRNA sequencing analysis and phylogenetic tree construction showed that the three strains were Bacillus tropicus, Pseudomonas multiresinivorans, and Raoultella terrigena. Under optimal degradation conditions, the maximal degradation rates were 67.30 ± 3.69%, 89.65 ± 1.08%, and 79.60 ± 5.30%, respectively, for YZQ-1, YZQ-3, and YZQ-4. Lipase activity was highest for YZQ-3, reaching 94.82 ± 12.89 U/L. The best bacterial alliance was obtained by adding equal numbers of microbial cells from the three strains. Moreover, when this bacterial alliance was applied to oily wastewater, the degradation rate of waste cooking oil was 61.13 ± 7.30% (3.67% ± 2.13% in the control group), and COD removal was 62.4% ± 5.65% (55.60% ± 0.71% in the control group) in 72 h. Microbial community analysis results showed YZQ-1 and YZQ-3 were adaptable to wastewater and could coexist with local bacteria, whereas YZQ-4 could not survive in wastewater. Therefore, the combination of YZQ-1 and YZQ-3 can efficiently degrade oil and shows great potential for oily wastewater treatment.