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Preparation and Application of Indoxacarb Degrading Bacteria Immobilized Sodium Alginate Microspheres
Scientia Agricultura Sinica 2022, 55(5): 920-931
Published: 01 March 2022
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【Objective】

The objective of this study is to prepare microsphere of degrading bacterium Pseudomonas stutzeri (ACCC 02521) with sodium alginate as carrier, and to establish the application conditions for degrading indoxacarb in farmland.

【Method】

Through the micro drop embedding ball forming method, bacteria were suspended and added into sodium alginate solution. After mixing, it was dropped into CaCl2 for granulation. It was washed with 0.9% NaCl after fixing at low temperature. The mass transfer performance and mechanical strength of degrading bacteria microspheres were measured to determine the optimal concentration of sodium alginate. The best formulation was obtained by single factor optimization. 1.0%-5.0% CaCl2, 40-200 g·L-1 bacteria or 20-100 g·L-1 preparation were dropped into 3.0% sodium alginate, respectively. The CaCl2 concentration, embedded bacteria and preparation dosage in the degrading bacteria microspheres were determined according to the degradation rate of indoxacarb. The morphology of microspheres, cell morphology and distribution of degrading bacteria were observed by scanning electron microscope. Quantitative degrading bacteria microspheres were put into different types of soil suspension, temperature, pH or treatment time. The effects of environmental factors on the release capacity, degradation effect and stability of degrading bacteria microspheres were evaluated by calculating the amount of released bacteria (CFU/mL) or the degradation rate of indoxacarb. Two days after the routine application of pesticides, the degrading bacteria microsphere preparation was applied. Topsoil was collected to detect the residue of indoxacarb, the field application of dose was determined, and the field application conditions of the preparation were determined. The residual concentrations of indoxacarb were detected and tracked by HPLC.

【Result】

The preparation was composed of 3.0% sodium alginate, 2.0% CaCl2 and 80 g·L-1 degrading bacteria. The particle size was about 3.0 mm. The degrading bacteria microspheres had uniform particle size, moderate mechanical strength, good mass transfer performance, degradation activity and storage stability. Scanning electron microscopy showed that the degrading bacteria were evenly distributed in sodium alginate microspheres and their morphology was normal. In the soil with 10-30℃ and pH of 6.0-8.0, the degrading bacteria were released stably, and the degradation rate of indoxacarb was more than 85%. The release performance was not affected by soil type, the stability was good, and was less affected by environmental conditions. When 90-900 kg·hm-2 of degrading bacteria microspheres were applied 2 d after field spraying of 150 g·L-1 of EC active ingredient 20 mg·L-1, the residual half-life (T1/2) of indoxacarb in soil was shortened to 2.49-3.32 d (7.53 d for blank control area); furthermore when 450 kg·hm-2 of degrading bacteria microspheres were applied 2 d after spraying indoxacarb with 5, 20 and 50 mg·L-1, the values of T1/2 was shortened from 6.03-7.45 d to 2.34-3.59 d.

【Conclusion】

The preparation of degrading bacteria P. stutzeri microspheres with sodium alginate as carrier has stable performance, can significantly degrade indoxacarb residues in farmland and shorten T1/2 time, provides technical and product support for bioremediation of soil pesticide residue pollution, and has the potential for further optimization and application.

Research Article Issue
Bioluminescent nanopaper for rapid screening of toxic substances
Nano Research 2018, 11(1): 114-125
Published: 02 August 2017
Abstract PDF (1.7 MB) Collect
Downloads:26

Environmental pollution is threatening human health and ecosystems as a result of modern agricultural techniques and industrial progress. A simple nanopaper-based platform coupled with luminescent bacteria Aliivibrio fischeri (A. fischeri) as a bio-indicator is presented here, for rapid and sensitive evaluation of contaminant toxicity. When exposed to toxicants, the luminescence inhibition of A. fischeri-decorated bioluminescent nanopaper (BLN) can be quantified and analyzed to classify the toxicity level of a pollutant. The BLN composite was characterized in terms of morphology and functionality. Given the outstanding biocompatibility of nanocellulose for bacterial proliferation, BLN achieved high sensitivity with a low cost and simplified procedure compared to conventional instruments for laboratory use only. The broad applicability of BLN devices to environmental samples was studied in spiked real matrices (lake and sea water), and their potential for direct and in situ toxicity screening was demonstrated. The BLN architecture not only survives but also maintains its function during freezing and recycling processes, endowing the BLN system with competitive advantages as a deliverable, ready-to-use device for large-scale manufacturing. The novel luminescent bacteria-immobilized, nanocelullose-based device shows outstanding abilities for toxicity bioassays of hazardous compounds, bringing new possibilities for cheap and efficient environmental monitoring of potential contamination.

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