Pulsed light (PL) is an emerging non-thermal sterilization technology, which inactivates microorganisms by short and high-intensity flash. In recent years, pulsed light technology has been widely used in food, medical and biosafety fields. The purpose of this study was to explore the inactivation mechanism of pulsed light on Bacillus subtilis NG-2.

I. Research background and significance

Bacillus subtilis NG-2 is a common soil bacterium with strong stress resistance and environmental adaptability. However, in some cases, such as food processing and biosafety, it needs to be effectively inactivated. As a new sterilization method, pulsed strong light technology has the advantages of rapidity, high efficiency and environmental protection. It has important theoretical and practical significance for the study of the inactivation mechanism of Bacillus subtilis NG-2.

Second, the principle of pulsed strong light technology

Pulsed bright light technology uses high-intensity, short-pulse flash to inactivate microorganisms. Its principle mainly includes photothermal effect, photochemical effect and photosensitization. Under the irradiation of pulsed strong light, the water, pigments and proteins in the microbial cells absorb light energy and convert it into heat energy, resulting in increased intracellular temperature and protein denaturation, thereby destroying the cell structure and achieving the purpose of inactivation.

III. Experimental materials and methods

Materials: Bacillus subtilis NG-2, pulsed light equipment, culture medium, etc.

Methods: The growth curve and the number of viable bacteria of Bacillus subtilis NG-2 were irradiated by pulsed light with different energy densities. At the same time, the effects of pulsed light on the morphological structure and biochemical characteristics of Bacillus subtilis NG-2 were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and fluorescence spectroscopy.

IV. Results and discussion

Inactivation effect: The inactivation rate of Bacillus subtilis NG-2 gradually increased with the increase of the energy density of pulsed strong light. When the energy density reaches a certain value, the complete inactivation of the bacteria can be achieved.

Changes in morphology and structure: SEM and TEM observations showed that the cell wall and cell membrane of Bacillus subtilis NG-2 were seriously damaged, the intracellular material leaked, and the cell morphology changed significantly after pulsed strong light irradiation.

Changes in biochemical characteristics: Fluorescence spectroscopy analysis showed that after pulsed strong light irradiation, the nucleic acid and protein structures of Bacillus subtilis NG-2 were damaged, resulting in a decrease in fluorescence intensity.

Based on the above results, it can be concluded that the inactivation mechanism of Bacillus subtilis NG-2 by pulsed strong light mainly includes photothermal effect and photochemical effect. Under the irradiation of pulsed strong light, the water, pigments and proteins in the cell absorb light energy and convert it into heat energy, resulting in an increase in intracellular temperature and protein denaturation, thereby destroying the cell structure. At the same time, high-energy flash may also trigger photochemical reactions of biological macromolecules in the cell, further destroying the cell structure and function.

V. Conclusions and Outlook

This study revealed the inactivation mechanism of pulsed glare on Bacillus subtilis NG-2, providing a theoretical basis for the application of pulsed glare technology in food, medical and biosafety fields. In the future, we can further explore the inactivation effect and mechanism of pulsed glare on other types of microorganisms, optimize the parameter setting of pulsed glare equipment, improve inactivation efficiency and reduce energy consumption. At the same time, we also need to pay attention to the safety and stability of pulsed glare technology in practical applications.