Comparative transcriptomic analysis reveals wavelength-dependent responses of Lactiplantibacillus plantarum under LED light irradiation

Lactiplantibacillus plantarum is widely used in food fermentation and probiotic applications owing to its metabolic versatility and environmental adaptability. Although light-emitting diode (LED) irradiation has emerged as a non-invasive strategy for modulating microbial physiology, its wavelength-dependent effects on L. plantarum remain unclear. We compared transcriptional responses of L. plantarum WCFS1 to red (630 nm), green (525 nm), and blue (470 nm) LEDs at 10 J/cm 2 and assessed extracellular metabolites, growth, intracellular reactive oxygen species (ROS), and oxidative DNA damage. Red and green irradiation primarily affected pathways associated with carbohydrate metabolism, nutrient transport, and arginine metabolism. Blue irradiation upregulated stress-related genes and pyrimidine metabolism while downregulating central carbon and fatty acid metabolism. Blue LEDs induced dose-dependent ROS accumulation, whereas red and green LEDs had no significant effect. Detectable 8-hydroxy-2′-deoxyguanosine accumulation occurred only under blue irradiation at 15 J/cm 2 , the highest fluence tested. LED irradiation also altered arginine depletion, glucose utilization, and lactic acid accumulation in a wavelength-dependent manner. Separate growth assays in defined medium showed reduced growth following blue irradiation. These findings demonstrate distinct wavelength-dependent metabolic and stress responses in L. plantarum and provide a basis for further investigation of LED-mediated modulation of lactic acid bacterial physiology.