Inactivation efficacy of 405 nm light emitting diodes (LEDs) on Salmonella Enteritidis at different illumination temperatures

Abstract

Salmonella Enteritidis is the major cause of foodborne salmonellosis affecting human health. The light emitting diodes (LEDs) is a novel approach to inactivate of the foodborne pathogens. The aim of this study was to determine the antibacterial effect of 405 nm LEDs illumination on S. Enteritidis and S. Enteritidis PT4. The irradiance of the 405 nm LEDs was 27.7 mW/cm 2 . Bacterial cultures suspended in tryptic soy broth were illuminated by 10-watt LEDs at a distance of 4.5 cm for 24 hours at 4 °C, 25 °C and 37 °C. Approximately 7-log reduction in colony forming unit (CFU) counts of both S. Enteritidis and S. Enteritidis PT4 at each temperature were observed following exposure after 7.5 hours to the LEDs, concluding that temperature did not affect the inactivation of the bacteria. The decimal reduction times (D-values) for the serotypes ranged from 55.78 to 67.88 min at 4, 25 and 37 °C after 405 nm LEDs illumination. No significant difference in D-values was observed among both the serotypes and temperatures, except for S. Enteritidis which had lower D-value at 4 °C. The LEDs technology has shown antibacterial efficacy and can be implemented in the food processing for reducing S. Enteritidis.

Curcumin and carvacrol mediated photodynamic inactivation with 405 nm light emitting diodes (LEDs) on Salmonella Enteritidis

“…Photodynamic inactivation (PDI) by LEDs has recently attracted the attention by researchers as a potential application for food preservation that can minimize food pathogens posing risks to consumer health (Gao and Matthews, 2020;Kim et al, 2017b). There are many studies showing the high antibacterial activity of LEDs between 405-420 nm against a wide variety of bacteria (Du et al, 2020;Keyvan et al, 2022a;Kim et al, 2015;Maclean et al, 2009) . Our previous work developed a 405 nm illuminating LEDs system for bacterial inactivation and examined its time-and temperature-dependent antibacterial activity against S. Enteritidis and S. Enteritidis PT4.…”

“…Carvacrol and curcumin were freshly dissolved each day in dimethyl-sulfoxide (DMSO) (Merck Millipore, 102952) (1:1, v: v) and later diluted in tryptic soy broth (TSB) (Oxoid, CM0876) before being applied. The minimal inhibition concentration (MIC) values of carvacrol (125.0 µg/mL) and curcumin (162.5 µg/mL) for S. Enteritidis and S. Enteritidis PT4, which were determined in our previous study (Keyvan et al, 2022a), were used to assess their photosensitizer activities in photodynamic inactivation experiments in this study. In the current study, we chose the amount of curcumin as two times the MIC value we found in the previous study.…”

“…A 405-nm LEDs light source was used for in vitro experiments. LEDs illumination system was designed and produced by using a 3D printer (Creality 3D CR-10S Pro V1, China) from acrylonitrile butadiene styrene (ABS) thermoplastic material according to the previous study conducted by Keyvan et al (2022aKeyvan et al ( , 2022b and Ghate et al (2013) with some modifications. The system consists of a light source (Shenzhen 10W 405 nm, China), a heat sink and a cooling fan (Arctic GmbH, Germany) assembly to avoid overheating.…”

“…The system consists of a light source (Shenzhen 10W 405 nm, China), a heat sink and a cooling fan (Arctic GmbH, Germany) assembly to avoid overheating. A photovoltaic power meter (Thorlabs PM100D/S130C sensor, USA) was used for light intensity measurements (Keyvan et al, 2022a;Sigma Aurum et al, 2019). In the current study, the 405 nm LEDs light dose was 49.0 mW/cm 2 .…”

“…Light-emitting diodes (LEDs) produce an antibacterial effect by PDI due to photosensitization of lightabsorbing compounds (a photosensitizer), which, in the presence of oxygen, lead to the formation of reactive oxygen species (ROS) such as singlet oxygen. The efforts to discover new compounds such as porphyrins, chlorins, phthalocyanines, fullerenes for PDI have grown dramatically in recent years (Benov, 2015;Keyvan et al, 2022a;Prasad et al, 2020). Therefore, this study aimed to evaluate the antibacterial activity of 405 nm LEDs application in the presence of carvacrol or curcumin against S. Enteritidis and S. Enteritidis PT4.…”