Pulsed electric fields (PEFs), which are generated by pulsed power technologies, are being tested for their applicability in food processing through protein conformational change and the poration of ...cell membranes. In this article, enzyme activity change and the permeabilization of agricultural products using pulsed power technologies are reviewed as novel, nonthermal food processes. Compact pulsed power systems have been developed with repetitive operation and moderate output power for application in food processing. Firstly, the compact pulsed power systems for the enzyme activity change and permeabilization are outlined. Exposure to electric fields affects hydrogen bonds in the secondary and tertiary structures of proteins; as a result, the protein conformation is induced to be changed. The conformational change induces an activity change in enzymes such as α-amylase and peroxidase. Secondly, the conformational change in proteins and the induced protein functional change are reviewed. The permeabilization of agricultural products is caused through the poration of cell membranes by applying PEFs produced by pulsed discharges. The permeabilization of cell membranes can be used for the extraction of nutrients and health-promoting agents such as polyphenols and vitamins. The electrical poration can also be used as a pre-treatment for food drying and blanching processes. Finally, the permeabilization of cell membranes and its applications in food processing are reviewed.
Sodium taurocholate cotransporting polypeptide (NTCP) is expressed at the surface of human hepatocytes and functions as an entry receptor of hepatitis B virus (HBV). Recently, we have reported that ...epidermal growth factor receptor (EGFR) is involved in NTCP-mediated viral internalization during the cell entry process. Here, we analyzed which function of EGFR is essential for mediating HBV internalization. In contrast to the reported crucial function of EGFR-downstream signaling for the entry of hepatitis C virus (HCV), blockade of EGFR-downstream signaling proteins, including mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase (PI3K), and signal transducer and activator of transcription (STAT), had no or only minor effects on HBV infection. Instead, deficiency of EGFR endocytosis resulting from either a deleterious mutation in EGFR or genetic knockdown of endocytosis adaptor molecules abrogated internalization of HBV via NTCP and prevented viral infection. EGFR activation triggered a time-dependent relocalization of HBV preS1 to the early and late endosomes and to lysosomes in concert with EGFR transport. Suppression of EGFR ubiquitination by site-directed mutagenesis or by knocking down two EGFR-sorting molecules, signal-transducing adaptor molecule (STAM) and lysosomal protein transmembrane 4β (LAPTM4B), suggested that EGFR transport to the late endosome is critical for efficient HBV infection. Cumulatively, these results support the idea that the EGFR endocytosis/sorting machinery drives the translocation of NTCP-bound HBV from the cell surface to the endosomal network, which eventually enables productive viral infection.
Inactivation of Bacillus subtilis spores on the surface of small spheres by dielectric barrier discharge (DBD) using relatively low AC high voltage (<10 kV0-p) for practical applications in the ...sterilization of small dried food was investigated. In this study the 6 and 10 mm gap distances were employed to place small dried foods inside the DBD, but a gap distance of more than 3 mm generally did not generate DBD at this applied voltage and atmospheric pressure. Therefore, the pressure was reduced to generate DBD and the relationship between discharge area rate and pressure was investigated using discharge area rate as the index. Low-pressure DBD (LPDBD) at 6 and 10 mm gap distances showed the maximum discharge area rates of 28% and 25% at 50 and 30 kPa, respectively. After 4 min treatment, B. subtilis spores on the surface of glass beads as the model of a small dried food were inactivated and the survival ratio decreased to 3.6 × 10−4 after the LPDBD treatment at 10 mm gap distance, and no viable cells were detected after the LPDBD treatment at 6 mm gap distance. Moreover, the humidification of the atmosphere was effective in improving the inactivation efficiency of LPDBD treatment, with which, B. subtilis spores were inactivated within 2 min of LPDBD treatment at 6 mm gap distance.
•Reducing the pressure allowed the generation of DBD in 6 and 10 mm gap distances using AC 10 kV0-p.•The relationship between the discharge area rate of PLDBD and pressure was concave down.•PLDBD treatment inactivated B. subtilis spores on the surface of glass beads.•The contribution of ozone produced by PLDBD to the inactivation of B. subtilis spores was small.•PLDBD treatment in humidified atmosphere inactivated B. subtilis spores within 2 min.
The engineering of pulsed electric field (PEF) reactors using carbon materials as the electrode was carried out to fundamentally eliminate the concern about the release of metallic ions into the ...treatment solution. PEF treatment using carbon cloth with a textile structure showed a strong inactivation effect on the inactivation Escherichia coli in a batch-type reactor. We also developed two continuous-flow-type PEF reactors: one allowed the treatment solution to flow parallel and the other perpendicular to the surface of the electrode. When the two reactors were compared, the latter showed higher sterilization capability. The effects of decreasing the flow rate of the treatment solution and increasing the electric field intensity on the inactivation of E. coli by PEF treatment were investigated. Although both improved the E. coli inactivation efficiency, the latter showed higher inactivation efficiency and a smaller increase in the temperature of the treatment solution. From the viewpoint of engineering for the pasteurization of liquid food, increasing the electric field intensity was more effective in the PEF treatment than decreasing the flow rate of the treatment solution. The continuous-flow-type PEF reactor with the carbon cloth electrode was applied to the pasteurization of sake, and although the sake yeast and Lactobacillus homohiochii in the sake were not inactivated to undetectable levels, they were significantly inactivated by continuous-flow PEF treatment.
•PEF treatment using carbon cloth as the electrode showed a strong inactivation effect.•A cross-flow reactor showed higher inactivation efficiency than a parallel-flow reactor.•Increasing the electric field intensity was effective for obtaining high inactivation efficiency.•Sake yeast and L. homohiochii in sake were significantly inactivated by continuous-flow PEF treatment.
In this study, a rotating nonthermal plasma (NTP) reactor was designed and its practical use for the inactivation of microorganisms on dried granular agricultural products such as black pepper was ...investigated. As the target microorganism to inactivate in the rotating NTP reactor, Aspergillus spores were artificially inoculated on whole black peppers. Inactivation treatments were carried out under several conditions. Rotating the NTP reactor facilitated the inactivation of the Aspergillus spores on the whole black peppers, and a decrease in the survival ratio of three orders (3 Log) was achieved after 4 min treatment. Using humidified gases for inactivation treatment in the rotating NTP reactor also facilitated the inactivation of the Aspergillus spores on the whole black peppers, and no viable spores of Aspergillus sp. were detected after 4 min treatment. The quality of the NTP- and dry-heat-treated whole black peppers was compared with that of untreated peppers in terms of the piperine content and antioxidative activity. The piperine contents of the NTP- and dry-heat-treated black peppers showed no significant difference, but the antioxidative activity in the NTP-treated peppers was higher than that in the dry-heat-treated peppers.
•A rotating non-thermal plasma (NTP) reactor was constructed and applied to the inactivation of Aspergillus sp. spores.•Rotating the NTP treatment reactor improved the inactivation efficiency of Aspergillus sp. spores.•The NTP treatment using humidified gases also enhanced the inactivation of Aspergillus sp. spores.•The antioxidative activity in NTP-treated whole black peppers remained relatively unaffected by the treatment.
Human T-cell leukaemia virus type-1 (HTLV-1) infection causes adult T-cell leukaemia (ATL). The viral protein HTLV-1 bZIP factor (HBZ) is constitutively expressed in ATL cells, suggesting that HBZ ...plays a major role in the pathogenesis of HTLV-1-associated disease. Here, we identified centromere protein B (CENP-B) as a novel interacting partner of HBZ. HBZ and CENP-B associate with their central regions in cells. Furthermore, overexpression of HBZ abrogated the DNA-binding activity of CENP-B to the α-satellite DNA region containing the CENP-B box motif, which in turn inhibited the CENP-B-mediated trimethylation of histone H3K9 in T-cells.
In this work, the bacterial inactivation effects of shock waves, ultraviolet (UV) light, and electric field produced by high-voltage pulsed discharge in liquid with needle-plate configurations were ...studied. The contributions of each effect on the bacterial killing ratio in the discharge process were obtained individually by modifying reactor type and usage of glass, quartz, and black balloons. The results showed that the location from the discharge center axis significantly influenced the effects of shock waves and electric fields, although the effect of UV light was not affected by the location in the reactor. The effects of shock waves and electric fields were improved by decreasing the distance from the discharge center axis. Under this experimental condition, the effects of shock waves, UV light, and electric fields produced by discharges on bacterial inactivation were approximately 36.1%, 30.8%, 12.7%, respectively. Other contributions seemed to be due to activated species.
•Bacterial inactivation effects of various substances from a discharge were studied.•Reactor location affects shock waves and electric fields, but not UV.•Effects of shock waves, electric fields improved with a short discharge center axis.
Longevity regulatory genes include the Forkhead transcription factor FOXO and the NAD-dependent histone deacetylase silent information regulator 2 (Sir2). Genetic studies demonstrate that Sir2 acts ...to extend lifespan in Caenorhabditis elegans upstream of DAF-16, a member of the FOXO family, in the insulin-like signaling pathway. However, the molecular mechanisms underlying the requirement of DAF-16 activity in Sir2-mediated longevity remain unknown. Here we show that reversible acetylation of Foxo1 (also known as FKHR), the mouse DAF-16 ortholog, modulates its transactivation function. cAMP-response element-binding protein (CREB)-binding protein binds and acetylates Foxo1 at the K242, K245, and K262 residues, the modification of which is involved in the attenuation of Foxo1 as a transcription factor. Conversely, Sir2 binds and deacetylates Foxo1 at residues acetylated by cAMP-response element-binding protein-binding protein. Sir2 is recruited to insulin response sequence-containing promoter and increases the expression of manganese superoxide dismutase and p27 kip1 in a deacetylase-activity-dependent manner. Our findings establish Foxo1 as a direct and functional target for Sir2 in mammalian systems.
Recently, pulsed power technologies, including pulsed electric fields (PEFs) and time-modulated plasmas, are starting to be applied actively in agriculture and food processing. In the applications, ...compact pulsed power generators with moderate peak power and repetitive operation are developed for controlling discharge plasmas and electric field distribution. These applications are mainly based on the biological effects of a spatially distributed electric field and the chemically active species in the plasma. The PEFs are caused by applying pulse voltage between the electrodes and contribute to form pores on the cell membrane or to change conformation of protein. When the applied voltage exceeds the discharge onset criterion, plasmas are generated through the avalanche process of electron accelerated with intense electric field in a gas or liquids medium. The plasmas produce chemically active species, UV radiation, an intense electric field in the vicinity of discharge channel and shock waves, which also have different biological effects. The agricultural applications of pulsed power can be categorized as two phases: pre-harvest and post-harvest phases. The pre-harvest phase consists of seed germination, seedling growth, plant growth and growth mode change from vegetative to reproductive. Pulsed power technologies are used to promotion of seed germination, plant growth enhancement through direct stimulation or indirect effect such as inactivation of bacteria in soil and liquid hydroponic media, and promotion of mushroom fruit body formation. The post-harvest phase consists of harvesting the agricultural produce, storing the products, transporting the products to consumers and food processing such as drying, pasteurization (sterilization of bacteria), permeabilization and fermentation. The pulsed power technologies are also used to keep freshness of agricultural produce through decontaminating airborne, inactivating bacteria and decomposition of plant hormone in the storage containers. The poration of cell membrane by PEF contributes improvement of extraction of juice, nutritional agents, and antioxidant metabolites such as polyphenols from agricultural products. In this review, at first, a basis of pulsed power system for agricultural applications and bio-effect by high-electric field exposure is outlined. After that, pre-harvest and post-harvest agricultural applications are described. The utilization of pulsed power technologies to contribute efficient food processing and improve food safety and quality is also described.
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