Low-energy Electron Beam Treatment Research Articles

Electron Beam Susceptibility of Enteric Viruses and Surrogate Organisms on Fruit, Seed and Spice Matrices

The objective of this study was to use high-energy electron beam (HEEB) treatments to find surrogate microorganisms for enteric viruses and to use the selected surrogates as proof of concept to investigate low-energy electron beam (LEEB) treatments for enteric virus inactivation at industrial scale on frozen blueberries. Six food matrices inoculated with HAV (hepatitis A virus), MNV S99 (murine norovirus), bacteriophages MS2 and Qβ, and Geobacillus stearothermophilus spores were treated with HEEB at 10 MeV using 4, 8 and 16 kGy doses. G. stearothermophilus spores showed the highest inactivation on all matrices except on raisins, with a dose-dependent effect. HAV reached the maximum measurable log10 reduction (> 3.2 log10) when treated at 16 kGy on raisins. MNV showed the highest resistance of all tested microorganisms, independent of the dose, except on frozen blueberries. On frozen blueberries, freeze-dried raspberries, sesame seeds and black peppercorns, HAV showed a mean inactivation level in between those of MS2 and G. stearothermophilus. Based on this, we selected both surrogate organisms as first approximation to estimate HAV inactivation on frozen blueberries during LEEB treatment at 250 keV using 16 kGy. Reductions of 3.1 and 1.3 log10 were measured for G. stearothermophilus spores and MS2, respectively, suggesting that a minimum reduction of 1.4 log10 can be expected for HAV under the same conditions.

Decontamination of herbs and spices by gamma irradiation and low-energy electron beam treatments and influence on product characteristics upon storage

ABSTRACT Culinary herbs and spices are an important sector of the food industry worldwide, but are often characterized by high levels of microbial contaminations. Therefore, irradiation is often applied to control the microbial burden. In this study, two spice decontamination technologies were compared: the established gamma irradiation as well as a newly developed low energy electron beam (LEEB) treatment. The aim of the study was to evaluate the efficacy of microbial surface inactivation for both treatments and their influence on quality attributes. Allspice berries, caraway seeds, oregano, and rosemary leaves were used as model matrices. Both treatments were shown to effectively reduce Enterococcus faecium counts below the detection limit (>3.3–5.5 log10). No differences in color, water activity, chlorophyll, and carotenoid contents, as well as 31 terpenoic compounds were determined between LEEB and gamma treatments in comparison to the untreated reference, for storage times of up to 105 days. Untargeted fingerprinting (SPME-GC-HRMS) showed a clustering of LEEB-treated rosemary samples, but no significant differences for the other samples.

Surface Modification and Adhesion Mechanism of Isotactic Polypropylene with Low-Energy Electron-Beam Treatments.

Recently, smaller-size electron-beam (EB) accelerators have offered EB irradiation in laboratory systems. Therefore, polymer surface treatments with low-energy EB have been developed in the past years. For high adhesion strength, low-energy EB treatment is also a promising method in comparison to plasma surface treatment. In the plasma treatment, the mechanism of the effect on the adhesion properties has been proved and the excess treatments led to the formation of a weak boundary layer and reduction of adhesion strength. In contrast, the low-energy EB possesses high penetration ability. In this work, we focused on the surface treatments of isotactic polypropylene (it.PP) with low-energy EB irradiation for adhesion. The dependence of adhesion strength on the absorbed dose of electron beam was evaluated, and the mechanism of electron beam on the adhesion properties was investigated from various perspectives of surface properties and morphology. Compared to that of plasma-treated it.PP, the adhesion strength of it.PP with electron-beam irradiation increased drastically. We proved that the radical was generated in the substrates after electron-beam treatments and would form covalent bonds between adhesives and substrates, which achieved higher adhesion than plasma treatments. In addition, the electron beam reached effectively a deep region from the top surface of the substrates and provided larger adhesion strength.

Structural transformations in Mn–Zn ferrite under low-energy electron beam treatment

We present the results of Mn–Zn ferrite treatment by a low-energy electron beam in the forevacuum pressure range. We have studied secondary recrystallization in Mn–Zn ferrite under the effect of a low-energy electron beam. It has been shown that the treatment by a low-energy electron beam results in a larger grain size and a denser near-surface layer. Additionally, this type of treatment decreases concentration of oxygen and zinc in the near-surface layer and causes partial deferritization.

Role of DNA repair in Bacillus subtilis spore resistance to high energy and low energy electron beam treatments

Bacillus subtilis spore inactivation mechanisms under low energy electron beam (LEEB) and high energy electron beam (HEEB) treatment were investigated using seven mutants lacking specific DNA repair mechanisms. The results showed that most of the DNA repair-deficient mutants, including ΔrecA, ΔKu ΔligD, Δexo Δnfo, ΔuvrAB and ΔsbcDC, had reduced resistances towards electron beam (EB) treatments at all investigated energy levels (80 keV, 200 keV and 10 MeV) compared to their wild type. This result suggested DNA damage was induced during EB treatments. The mutant lacking recA showed the lowest resistance, followed by the mutant lacking Ku and ligD. These findings indicated that recA, Ku and ligD and their associated DNA repair mechanisms, namely, homologous recombination and non-homologous end joining, play important roles in spore survival under EB treatment. Furthermore, exoA, nfo, uvrAB, splB, polY1 and polY2, which are involved in nucleotide damage repair/removal, showed different levels of effects on spore resistance under EB treatment. Finally, the results suggested that HEEB and LEEB inactivate B. subtilis spores through similar mechanisms. This research will provide a better understanding of how EB technologies inactivate B. subtilis spores and will contribute to the application of these technologies as a non-thermal, gentle spore control approach.

Geobacillus and Bacillus Spore Inactivation by Low Energy Electron Beam Technology: Resistance and Influencing Factors.

Low energy electron beam (LEEB) treatment is an emerging non-thermal technology that performs surface decontamination with a minimal influence on food quality. Bacterial spore resistance toward LEEB treatment and its influencing factors were investigated in this study. Spores from Geobacillus and Bacillus species were treated with a lab-scale LEEB at energy levels of 80 and 200 keV. The spore resistances were expressed as D-values (the radiation dose required for one log10 reduction at a given energy level) calculated from the linear regression of log10 reduction against absorbed dose of the sample. The results revealed that the spore inactivation efficiency by LEEB is comparable to that of other ionizing radiations and that the inactivation curves are mostly log10-linear at the investigated dose range (3.8 – 8.2 kGy at 80 keV; 6.0 – 9.8 kGy at 200 keV). The D-values obtained from the wildtype strains varied from 2.2 – 3.0 kGy at 80 keV, and from 2.2 – 3.1 kGy at 200 keV. Bacillus subtilis mutant spores lacking α/β-type small, acid-soluble spore proteins showed decreased D-values (1.3 kGy at 80 and 200 keV), indicating that spore DNA is one of the targets for LEEB spore inactivation. The results revealed that bacterial species, sporulation conditions and the treatment dose influence the spore LEEB inactivation. This finding indicates that for the application of this emerging technology, special attention should be paid to the choice of biological indicator, physiological state of the indicator and the processing settings. High spore inactivation efficiency supports the application of LEEB for the purpose of food surface decontamination. With its environmental, logistical, and economic advantages, LEEB can be a relevant technology for surface decontamination to deliver safe, minimally processed and additive-free food products.

Low-energy electron-beam treatment as alternative for on-site sterilization of highly functionalized medical products – A feasibility study

Over the last decades, the medical device industry has grown significantly. Complex and highly functionalized medical devices and implants are being developed to improve patient treatment and to enhance their health-related quality of life. However, medical devices from this new generation often cannot be sterilized by standard methods such as autoclaving or sterilizing gases, as they are temperature sensitive, containing electronic components like sensors and microchips, or consist of polymers. Gamma irradiation for sterilization of such products is also problematic due to long processing times under highly reactive conditions resulting in material degradation or loss of functionality. Low-energy electron-beam treatment could enable irradiation sterilization of medical surfaces within seconds. This method is very fast in comparison to gamma irradiation because of its high dose rate and therefore degradation processes of polymers can be reduced or even prevented. Additionally, electron penetration depth can be precisely controlled to prevent damage of sensitive components like electronics and semiconductors.The presented study focuses on two key aspects: 1.) Can new and highly functionalized medical products in future be sterilized using low-energy electron-beam irradiation; and 2.) Is the low-energy electron-beam technology suitable to be set up on-site to speed up sterilization processing or make it available “just-in-time”. To address these questions, different test specimens were chosen with complex geometry or electronic functional parts to gather information about the limitations and chances for this new approach. The test specimens were inoculated with clinical relevant test organisms (Pseudomonas aeruginosa) as well as with approved radiation resistant organisms (Deinococcus radiodurans and Bacillus pumilus) to prove the suitability of low-energy electron-beam treatment for the above-mentioned medical products. The calculation of the D10 value for B. pumilus revealed equal efficacy when compared to standard high-energy irradiation sterilization. All of the above-mentioned germs were successfully inactivated by low-energy electron-beam treatment when test specimens were inoculated with a germ load > 10^6 CFU and treated with doses ≥ 10 kGy (for B. pumilus and P. aeruginosa) and > 300 kGy (for D. radiodurans) respectively. As an example, for specialized electronic components to be sterilized, an impedance sensor for cell culture applications was sterilized and unimpaired functionality was demonstrated even after five repeated sterilization cycles to a total dose of 50 kGy. To address the second aspect of on-site suitability of this technology, the product handling for low-energy electron-beam treatment had to be adapted to minimize the size of the electron-beam facility. Therefore, a mini electron-beam source was used and a specialized sample holder and 3D-handling regime were developed to allow reproducible surface treatment for complex product geometries. Inactivation of B. pumilus inoculated medical screws (> 10^6 CFU) was successful using the developed handling procedure. In addition, a packaging material (PET12/PE50) for medical products was investigated for its suitability for low-energy irradiation sterilization. Biocompatibility assessment revealed the material to be eligible for this application as even overdoses did not impair the biocompatibility of the material.With these results, the principal suitability of low-energy electron-beam treatment for sterilization of medical products containing electronics like sensors is demonstrated. The low-energy technology and the specialized 3D-handling regime allow the on-site setup of the technology in hospitals, medical practices or any other point of care.

Long-term stable surface modification of DLC coatings

Abstract The use of coatings based on diamond like carbon (DLC) for medical applications was established during the last years. Main advantages of these coatings are its high hardness, good wear and friction behavior and its biocompatibility. Using low-energy electron-beam treatment, we addressed the surface modification of DLC coatings. The aim was to generate new biofunctional surface characteristics that are long-term stable. Electron-beam modification resulted in significantly increased surface hydrophilicity, giving rise to the conclusion, that biological reaction on these surfaces will also be influenced by the modification. Furthermore, the stability of the surface modification was investigated. Therefore, the modified samples were stored for 8 weeks under ambient conditions. Additionally, the samples were stored in physiological saline solution at 37°C for 8 weeks. The stability of the modification was analyzed by contact angle measurement confirming no changes over the whole period of storage. In addition, the stability against standard cleaning and sterilization procedures was investigated. The durability of the modification to withstand these cleaning procedures was also proven. With these findings, the low-energy electron-beam modification seems to be a suitable tool for surface modification of DLC coatings. Thereby, the very good long-term stability is a great improvement in comparison to conventional surface modification methods like plasma treatment. In order to investigate the suitability of the modified coatings for biomedical applications, the cellular response was investigated using human fibroblasts, revealing a significantly reduced cell count on modified surfaces while maintaining their biocompatibility. By modification of the DLC surfaces, it is possible to adapt the cell adhesion on the treated surface areas. These findings demonstrate electron-beam treatment to be applicable for partial surface modification and functionalization within biomedical applications.

Rapid, room temperature sterilization of plastic container using low energy electron beam treatment

Rapid, room temperature sterilization of plastic container using low energy electron beam treatment

Low energy electron beam treatment of VOCs

Research on electron beam decomposition of volatile organic compounds (VOCs) in air was carried out to establish an advanced treatment technology for industrial off-gases. Benzene, toluene and o-xylene were selected as aromatic VOCs and dichloro-, trichloro- and tetrachloro-ethylene as chloroethenes. The experimental results showed that G-values of decomposition ranged from 1.0–2.2 in aromatic compounds and 30–60% of decomposed compounds were converted into aerosols. On the other hand, G-values of decomposition of chloroethenes increased with the initial concentration and number of chlorine atoms in a molecule, for example, the G-value at 180 and 1580 ppm of tetrachloroethylene were 22 and 172, respectively. The formation of aerosol was not observed in the decomposition of chloroethenes. An application of low energy electron accelerator for treatment of exhaust gases containing VOCs was also discussed.