Carton sterilization by u.v.-C excimer laser light: recovery of Bacillus subtilis spores on vegetable extracts and food simulation matrices

Abstract

Aims: To determine the recovery of Bacillus subtilis spores loaded onto preformed cartons and irradiated with u.v.-excimer laser (248 nm) light. Methods and Results: Bacillus subtilis spores irradiated with u.v.-excimer laser light retained phase brightness, but were blocked at various stages of germination. In the presence of germinant, the majority of spores began to lose phase brightness but only after an extended lag period (ca 90 min). After 6 h ca 9% of the spores had elongated but failed to form new cells, approx. 12% had undergone partial phase darkening (grey spores), 15% remained phase bright whilst the remainder had turned fully phase dark but failed to elongate. No enhanced recovery of u.v.-treated spores (with intact or permeabilized coats) occurred in media containing hen egg white lysozyme or vegetable extracts (celery, carrot, swede or turnip). However, recovery did occur when irradiated spores were incubated for 26 d, semiaerobically, within cartons containing nutrient broth or milk. Conclusions: The germination ability of B. subtilis spores is altered following u.v.-excimer laser treatment. Recovery of treated spores was found in liquid systems but not on agar plates supplemented with vegetable extracts or lysozyme. Significance and Impact of the Study: The potential recovery of u.v.-excimer laser-treated spores in a range of carton-packed food systems requires further investigation.

In Vitro Bactericidal Effects of 625, 525, and 425 nm Wavelength (Red, Green, and Blue) Light-Emitting Diode Irradiation

“…[1][2][3][4][5] UV is used extensively for disinfection of drinking water, treatment of plants, and in clinical and industrial facilities to prevent bacterial infection. 6,7 The sterilization efficiency of UV systems depends upon different parameters such as wavelength range and microbial concentration.…”

Decontamination of N95 and surgical masks using a treatment based on a continuous gas phase-Advanced Oxidation Process

“…The Advanced Oxidation process has previously been applied for degrading pollutants in water treatment [22] with the gas-phase treatment (gAOP) receiving less attention. Yet, a gAOP process has a history of use in carton packaging decontamination whereby UV-C (254 nm) mediated degradation of 1% v/v hydrogen peroxide can support >5 log CFU inactivation of Bacillus endospores [23][24][25]. More recently, gAOP has been applied to inactivate pathogens such as Listeria monocytogenes on fresh fruit and vegetables [21,26].…”

Synergistic effect of UV, laser and microwave radiation or conventional heating on E. coli and on some spoilage and pathogenic bacteria

“…Use of pulsed ultraviolet laser light for the cold pasteurization of bovine milk has been investigated (Smith, Lagunas-Solar, & Cullor, 2002). Also UV excimer lasers have been used to inactivate Bacillus subtilis spores to sterilise packaging cartons (Warriner, Kolstad, Rumsby, & Waites, 2002) and packaging surfaces (Warriner et al, 2000) related to the food industry.…”