Long-Chain Hydrocarbons from Nonthermal Plasma-Driven Biogas Upcycling.

The burgeoning necessity to discover new methodologies for the synthesis of long-chain hydrocarbons and oxygenates, independent of traditional reliance on high-temperature, high-pressure, and fossil fuel-based carbon, is increasingly urgent. In this context, we introduce a nonthermal plasma-based strategy for the initiation and propagation of long-chain carbon growth from biogas constituents (CO2 and CH4). Utilizing a plasma reactor operating at atmospheric room temperature, our approach facilitates hydrocarbon chain growth up to C40 in the solid state (including oxygenated products), predominantly when CH4 exceeds CO2 in the feedstock. This synthesis is driven by the hydrogenation of CO2 and/or amalgamation of CHx radicals. Global plasma chemistry modeling underscores the pivotal role of electron temperature and CHx radical genesis, contingent upon varying CO2/CH4 ratios in the plasma system. Concomitant with long-chain hydrocarbon production, the system also yields gaseous products, primarily syngas (H2 and CO), as well as liquid-phase alcohols and acids. Our finding demonstrates the feasibility of atmospheric room-temperature synthesis of long-chain hydrocarbons, with the potential for tuning the chain length based on the feed gas composition.

Catalyst-Free Carbon Dioxide Conversion in Water Facilitated by Pulse Discharges.

By inducing CO2-pulsed discharges within microchannel bubbles and regulating thus-forming plasma microbubbles, we observe high-performance, catalyst-free coformation of hydrogen peroxide (H2O2) and oxalate directly from CO2 and water. With isotope-labeled C18O2 as the feedstock, peaks of H218O16O and H216O2 observed by ex situ surface-enhanced Raman spectra indicate that single-atom oxygen (O) from CO2 dissociations and H2O-derived OH radicals both contribute to H2O2 formation. The global plasma chemistry modeling suggests that high-density, energy-intense electron supply enables high-density CO2- (aq) and HCO2- (aq) formation and their subsequent coupling to produce oxalate. The enhanced solvation of CO2, facilitated by the efficient transport of CxOy ionic species and CO, is demonstrated as a crucial benefit of spark discharges interacting with water at the bubble interface. We expect this plasma microbubble approach to provide a novel power-to-chemical avenue to convert CO2 into valuable H2O2 and oxalic acid platform chemicals, thus leveraging renewable energy resources.

Guidelines on reporting treatment conditions for emerging technologies in food processing.

In the last decades, different non-thermal and thermal technologies have been developed for food processing. However, in many cases, it is not clear which experimental parameters must be reported to guarantee the experiments' reproducibility and provide the food industry a straightforward way to scale-up these technologies. Since reproducibility is one of the most important science features, the current work aims to improve the reproducibility of studies on emerging technologies for food processing by providing guidelines on reporting treatment conditions of thermal and non-thermal technologies. Infrared heating, microwave heating, ohmic heating and radiofrequency heating are addressed as advanced thermal technologies and isostatic high pressure, ultra-high-pressure homogenization sterilization, high-pressure homogenization, microfluidization, irradiation, plasma technologies, power ultrasound, pressure change technology, pulsed electric fields, pulsed light and supercritical CO2 are approached as non-thermal technologies. Finally, growing points and perspectives are highlighted.

The antimicrobial efficacy of plasma-activated water against Listeria and E. coli is modulated by reactor design and water composition.

AIMS: This study aimed to compare the efficacy of plasma-activated water (PAW) generated by two novel plasma reactors against pathogenic foodborne illness organisms. METHODS AND RESULTS: The antimicrobial efficacy of PAW produced by a bubble spark discharge (BSD) reactor and a dielectric barrier discharge-diffuser (DBDD) reactor operating at atmospheric conditions with air, multiple discharge frequencies and Milli-Q and tap water, was investigated with model organisms Listeria innocua and Escherichia coli in situ. Optimal conditions were subsequently employed for pathogenic bacteria Listeria monocytogenes, E. coli and Salmonella enterica. DBDD-PAW reduced more than 6-log of bacteria within 1 min. The BSD-PAW, while attaining high log reduction, was less effective. Analysis of physicochemical properties revealed that BSD-PAW had a greater variety of reactive species than DBDD-PAW. Scavenger assays designed to specifically sequester reactive species demonstrated a critical role of superoxide, particularly in DBDD-PAW. CONCLUSIONS: DBDD-PAW demonstrated rapid antimicrobial activity against pathogenic bacteria, with superoxide the critical reactive species. SIGNIFICANCE AND IMPACT OF STUDY: This study demonstrates the potential of DBDD-PAW produced using tap water and air as a feasible and cost-effective option for antimicrobial applications, including food safety.

Platinum nanoparticles inhibit intracellular ROS generation and protect against cold atmospheric plasma-induced cytotoxicity.

Platinum nanoparticles (PtNPs) have been investigated for their antioxidant abilities in a range of biological and other applications. The ability to reduce off-target cold atmospheric plasma (CAP) cytotoxicity would be useful in Plasma Medicine; however, little has been published to date about the ability of PtNPs to reduce or inhibit the effects of CAP. Here we investigate whether PtNPs can protect against CAP-induced cytotoxicity in cancerous and non-cancerous cell lines. PtNPs were shown to dramatically reduce intracellular reactive species (RONS) production in U-251 MG cells. However, RONS generation was unaffected by PtNPs in medium without cells. PtNPs protect against CAP induced mitochondrial membrane depolarization, but not cell membrane permeabilization which is a CAP-induced RONS-independent event. PtNPs act as potent intracellular scavengers of reactive species and can protect against CAP induced cytotoxicity. PtNPs, showing no significant biocorrosion, may be useful as a catalytic antioxidant for healthy tissue and for protecting against CAP-induced tissue damage.

Inactivation Efficacies and Mechanisms of Gas Plasma and Plasma-Activated Water against Aspergillus flavus Spores and Biofilms: a Comparative Study.

Atmospheric cold plasma (ACP) treatment is an emerging food technology for product safety and quality retention, shelf-life extension, and sustainable processing. The activated chemical species of ACP can act rapidly against microorganisms without leaving chemical residues on food surfaces. The main objectives of this study were to investigate the efficiency and mechanisms of inactivation of fungal spores and biofilms by ACP and to understand the effects of the gas-mediated and liquid-mediated modes of application against important fungal contaminants. Aspergillus flavus was selected as the model microorganism. A. flavus spores were exposed to either gas plasma (GP) or plasma-activated water (PAW), whereas gas plasma alone was used to treat A. flavus biofilms. This study demonstrated that both GP and PAW treatments independently resulted in significant decreases of A. flavus metabolic activity and spore counts, with maximal reductions of 2.2 and 0.6 log10 units for GP and PAW, respectively. The characterization of the reactive oxygen and nitrogen species in PAW and spore suspensions indicated that the concentration of secondary reactive species was an important factor influencing the antimicrobial activity of the treatment. The biofilm study showed that GP had detrimental effects on biofilm structure; however, the initial inoculum concentration prior to biofilm formation can be a crucial factor influencing the fungicidal effects of ACP.IMPORTANCE The production of mycotoxin-free food remains a challenge in both human and animal food chains. A. flavus, a mycotoxin-producing contaminant of economically important crops, was selected as the model microorganism to investigate the efficiency and mechanisms of ACP technology against fungal contaminants of food. Our study directly compares the antifungal properties of gas plasma (GP) and plasma-activated water (PAW) against fungi as well as reporting the effects of ACP treatment on biofilms produced by A. flavus.

Cold atmospheric plasma induces silver nanoparticle uptake, oxidative dissolution and enhanced cytotoxicity in glioblastoma multiforme cells.

Silver nanoparticles (AgNP) emerged as a promising reagent for cancer therapy with oxidative stress implicated in the toxicity. Meanwhile, studies reported cold atmospheric plasma (CAP) generation of reactive oxygen and nitrogen species has selectivity towards cancer cells. Gold nanoparticles display synergistic cytotoxicity when combined with CAP against cancer cells but there is a paucity of information using AgNP, prompting to investigate the combined effects of CAP using dielectric barrier discharge system (voltage of 75 kV, current is 62.5 mA, duty cycle of 7.5kVA and input frequency of 50-60Hz) and 10 nm PVA-coated AgNP using U373MG Glioblastoma Multiforme cells. Cytotoxicity in U373MG cells was >100-fold greater when treated with both CAP and PVA-AgNP compared with either therapy alone (IC50 of 4.30 µg/mL with PVA-AgNP alone compared with 0.07 µg/mL after 25s CAP and 0.01 µg/mL 40s CAP). Combined cytotoxicity was ROS-dependent and was prevented using N-Acetyl Cysteine. A novel darkfield spectral imaging method investigated and quantified AgNP uptake in cells determining significantly enhanced uptake, aggregation and subcellular accumulation following CAP treatment, which was confirmed and quantified using atomic absorption spectroscopy. The results indicate that CAP decreases nanoparticle size, decreases surface charge distribution of AgNP and induces uptake, aggregation and enhanced cytotoxicity in vitro.

Effects of Nonthermal Plasma Technology on Functional Food Components.

Understanding the impact of nonthermal plasma (NTP) technology on key nutritional and functional food components is of paramount importance for the successful adoption of the technology by industry. NTP technology (NTPT) has demonstrated marked antimicrobial efficacies with good retention of important physical, chemical, sensory, and nutritional parameters for an array of food products. This paper presents the influence of NTPT on selected functional food components with a focus on low-molecular-weight bioactive compounds and vitamins. We discuss the mechanisms of bioactive compound alteration by plasma-reactive species and classify their influence on vitamins and their antioxidant capacities. The impact of NTP on specific bioactive compounds depends both on plasma properties and the food matrix. Induced changes are mainly associated with oxidative degradation and cleavage of double bonds in organic compounds. The effects reported to date are mainly time-dependent increases in the concentrations of polyphenols, vitamin C, or increases in antioxidant activity. Also, improvement in the extraction efficiency of polyphenols is observed. The review highlights future research needs regarding the complex mechanisms of interaction with plasma species. NTP is a novel technology that can both negatively and positively affect the functional components in food.

Surface attachment of active antimicrobial coatings onto conventional plastic-based laminates and performance assessment of these materials on the storage life of vacuum packaged beef sub-primals.

Two antimicrobial coatings, namely Sodium octanoate and Auranta FV (a commercial antimicrobial composed of bioflavonoids, citric, malic, lactic, and caprylic acids) were used. These two antimicrobials were surface coated onto the inner polyethylene layer of cold plasma treated polyamide films using beef gelatin as a carrier and coating polymer. This packaging material was then used to vacuum pack beef sub-primal cuts and stored at 4 °C. A control was prepared using the non-coated commercial laminate and the same vacuum packaged sub-primal beef cuts. During storage, microbial and quality assessments were carried out. Sodium octanoate treated packages significantly (p < 0.05) reduced microbial counts for all bacteria tested with an increase of 7 and 14 days, respectively compared to control samples. No significant effect on pH was observed with any treatment. The results suggested that these food grade antimicrobials have the potential to be used in antimicrobial active packaging applications for beef products.

Non-thermal atmospheric plasma induces ROS-independent cell death in U373MG glioma cells and augments the cytotoxicity of temozolomide.

BACKGROUND: Non-thermal atmospheric plasma (NTAP) is an ionised gas produced under high voltage that can generate short-lived chemically active species and induce a cytotoxic insult in cancer cells. Cell-specific resistance to NTAP-mediated cytotoxicity has been reported in the literature. The aim of this study was to determine whether resistance against NTAP could be overcome using the human glioma cell line U373MG. METHODS: Non-thermal atmospheric plasma was generated using a Dielectric Barrier Device (DBD) system with a maximum voltage output of 120 kV at 50 Hz. The viability of U373MG GBM cells and HeLa cervical carcinoma cells was determined using morphology, flow cytometry and cytotoxicity assays. Fluorescent probes and inhibitors were used to determine the mechanisms of cytotoxicity of cells exposed to the plasma field. Combinational therapy with temozolomide (TMZ) and multi-dose treatments were explored as mechanisms to overcome resistance to NTAP. RESULTS: Non-thermal atmospheric plasma decreased cell viability in a dose (time)-dependent manner. U373MG cells were shown to be resistant to NTAP treatment when compared with HeLa cells, and the levels of intracellular reactive oxygen species (ROS) quantified in U373MG cells were much lower than in HeLa cells following exposure to the plasma field. Reactive oxygen species inhibitor N-acetyl cysteine (NAC) only alleviated the cytotoxic effects in HeLa cells and not in the relatively NTAP-resistant cell line U373MG. Longer exposures to NTAP induced a cell death independent of ROS, JNK and caspases in U373MG. The relative resistance of U373MG cells to NTAP could be overcome when used in combination with low concentrations of the GBM chemotherapy TMZ or exposure to multiple doses. CONCLUSIONS: For the very first time, we report that NTAP induces an ROS-, JNK- and caspase-independent mechanism of cell death in the U373MG GBM cell line that can be greatly enhanced when used in combination with low doses of TMZ. Further refinement of the technology may facilitate localised activation of cytotoxicity against GBM when used in combination with new and existing chemotherapeutic regimens.

Multipoint near-infrared spectrometry for real-time monitoring of protein conformational stability in powdered infant formula.

Powdered infant formula (PIF) can be the sole source of nutrition for babies and infants. Monitoring conformational changes in protein during manufacture of PIF is critical in order to maintain its nutritional value. This study presents the development of a calibration model for monitoring conformational changes in PIF protein by applying a novel multipoint near-infrared (NIR) spectrometry. NIR spectra were collected for PIF and PIF proteins, casein and whey protein isolate, before and after heat treatment. Results show that principal component analysis showed discrimination between native protein at room temperature and protein conformational changes caused at elevated temperature. Partial least squares regression analysis showed good calibration models with correlation coefficients ranging between 87% and 99% for the prediction of protein quality. This novel multipoint NIR spectrometry could serve as a simple in-line tool to rapidly monitor protein quality during processing stages, contributing to product nutritional value.

Survival of Listeria Strains and Shelf Life Determination of Fresh Blueberries (Vaccinium corymbosum) Treated with Cold Atmospheric Plasma.

Fresh blueberries are delicate, hand-picked, packaged, and refrigerated fruits vulnerable to spoilage and contamination. Cold atmospheric plasma (CAP) is a promising antimicrobial technology; therefore, this study evaluated the CAP treatment effect on acid-tolerant Listeria innocua and Listeria monocytogenes and evaluated changes in the quality of the treated fruit. Samples were spot-inoculated with pH 5.5 and 6.0 acid-adapted Listeria species. Samples were treated with gliding arc CAP for 15, 30, 45, and 60 s and evaluated after 0, 1, 4, 7, and 11 days of storage at 4 °C and 90% humidity for the following quality parameters: total aerobic counts, yeast and molds, texture, color, soluble solids, pH, and titratable acidity. CAP treatments of 30 s and over demonstrated significant reductions in pathogens under both the resistant strain and pH conditions. Sixty-second CAP achieved a 0.54 Log CFU g-1 reduction in L. monocytogenes (pH 5.5) and 0.28 Log CFU g-1 for L. monocytogenes (pH 6.0). Yeast and mold counts on day 0 showed statistically significant reductions after 30, 45, and 60 s CAP with an average 2.34 Log CFU g-1 reduction when compared to non-CAP treated samples. Quality parameters did not show major significant differences among CAP treatments during shelf life. CAP is an effective antimicrobial treatment that does not significantly affect fruit quality.

Advances in 3D culture systems for therapeutic discovery and development in brain cancer.

This review focuses on recent advances in 3D culture systems that promise more accurate therapeutic models of the glioblastoma multiforme (GBM) tumor microenvironment (TME), such as the unique anatomical, cellular, and molecular features evident in human GBM. The key components of a GBM TME are outlined, including microbiomes, vasculature, extracellular matrix (ECM), infiltrating parenchymal and peripheral immune cells and molecules, and chemical gradients. 3D culture systems are evaluated against 2D culture systems and in vivo animal models. The main 3D culture techniques available are compared, with an emphasis on identifying key gaps in knowledge for the development of suitable platforms to accurately model the intricate components of the GBM TME.

Three-Dimensional (3D) in vitro cell culture protocols to enhance glioblastoma research.

Three-dimensional (3D) cell culture models can help bridge the gap between in vitro cell cultures and in vivo responses by more accurately simulating the natural in vivo environment, shape, tissue stiffness, stressors, gradients and cellular response while avoiding the costs and ethical concerns associated with animal models. The inclusion of the third dimension in 3D cell culture influences the spatial organization of cell surface receptors that interact with other cells and imposes physical restrictions on cells in compared to Two-dimensional (2D) cell cultures. Spheroids' distinctive cyto-architecture mimics in vivo cellular structure, gene expression, metabolism, proliferation, oxygenation, nutrition absorption, waste excretion, and drug uptake while preserving cell-extracellular matrix (ECM) connections and communication, hence influencing molecular processes and cellular phenotypes. This protocol describes the in vitro generation of tumourspheroids using the low attachment plate, hanging drop plate, and cellusponge natural scaffold based methods. The expected results from these protocols confirmed the ability of all these methods to create uniform tumourspheres.

The antimicrobial effects of mist spraying and immersion on beef samples with plasma-activated water.

The use of plasma-activated water (PAW) as an antimicrobial agent to inactivate Salmonella Typhimurium on chilled beef during meat washing was evaluated. Two meat washing methods, spraying and immersion, were evaluated at contact times of 15, 30 and 60 s and meat storage times of 0, 1 and 7 days. The temperature of PAW was elevated to 55 °C for washing as it increased the microbial inactivation compared to ambient temperature. At the contact time of 60 s and meat storage time of 7 days, PAW spraying and immersion achieved 0.737-log10 and 0.710-log10 reductions against Salmonella Typhimurium, respectively; there were no significant differences between both washing methods, with spraying being preferred for commercial implementation. Compared to untreated and water-treated samples, meat washing with PAW alone improved the S. Typhimurium inactivation and did not cause negative impacts on the lightness and hue angle values, TBARS value, water holding capacity and pH. However, PAW reduced the redness, yellowness and chroma values with the decreased oxymyoglobin values of 44.1% at the storage time of 1 day. PAW spraying at 55 °C followed by additional water washing at 25 °C for 60 s achieved 0.696-log10 reduction and mitigated a reduction in (i) the redness value, from 11.3 to 18.2, (ii) the yellowness value, from 9.19 to 11.1, and (iii) the chroma value, from 14.5 to 21.3, without displaying colour differences (∆E), as detected by human eyes, compared to water-treated samples. Moreover, the content of myoglobin forms was maintained by additional water washing.

Inulin for surimi gel fortification: Performance and molecular weight-dependent effects.

Inulin is a prebiotic carbohydrate widely used in food industry due to its health benefits and unique rheological properties. For the first time, this study explores the potential of natural inulin as a sustainable food additive to enhance surimi gel characteristics, specifically focusing on understanding its molecular weight effects. The good solubility of inulin facilitates the conversion of α-helix to other secondary conformations which are favorable for protein denaturation and aggregation during gelation. Moreover, the abundant -OH groups at the surface of inulin can boost the chemical forces within surimi proteins to reinforce the gel network. Compared to short-chain inulin, long-chain inulin can alleviate proteolysis, enhance hydrophobic interactions and intertwine with myosin molecules, thereby reinforcing the gel network. A more viscous long-chain inulin solution formed within surimi gels fills the space between aggregated proteins and facilitates the lock of water molecules, improving the water-holding capacity (WHC). Thus, an addition of 12 % long-chain inulin leads to an enhanced hardness of surimi gel from 943 to 1593 and improved WHC from 72 % to 85 %. A new inulin-myosin interaction mechanism model is also proposed to provide useful guidelines for surimi processing and expanding the application of inulin within the food industries.

A polymeric hydrogel electrocatalyst for direct water oxidation.

Metal-free electrocatalysts represent a main branch of active materials for oxygen evolution reaction (OER), but they excessively rely on functionalized conjugated carbon materials, which substantially restricts the screening of potential efficient carbonaceous electrocatalysts. Herein, we demonstrate that a mesostructured polyacrylate hydrogel can afford an unexpected and exceptional OER activity - on par with that of benchmark IrO2 catalyst in alkaline electrolyte, together with a high durability and good adaptability in various pH environments. Combined theoretical and electrokinetic studies reveal that the positively charged carbon atoms within the carboxylate units are intrinsically active toward OER, and spectroscopic operando characterizations also identify the fingerprint superoxide intermediate generated on the polymeric hydrogel backbone. This work expands the scope of metal-free materials for OER by providing a new class of polymeric hydrogel electrocatalysts with huge extension potentials.

Efficacy of Chitosan Oligosaccharide Combined with Cold Atmospheric Plasma for Controlling Quality Deterioration and Spoilage Bacterial Growth of Chilled Pacific White Shrimp (Litopenaeus vannamei).

A novel food processing technique based on the combination of cold atmospheric plasma (CAP) and chitosan oligosaccharide treatment (COS) was developed to enhance antibacterial performance and extend the shelf life of Pacific white shrimp (Litopenaeus vannamei). Effects of different treatments on the microbial community composition, physicochemical properties, and post-storage behaviors of Pacific white shrimp were evaluated during chilled storage for up to 10 days. Results showed that the synergistic effects of COS and CAP could be obtained, largely inhibiting the growth of microorganisms. The content of total volatile basic nitrogen (TVB-N), total viable counts (TVC), and pH value in treated groups were lower than in the control group and the loss of moisture content, water activity, and sensory score were observed. Compared to the control group, shrimp was on the verge of spoilage on the 6th day of storage, while the COS-CAP-treated shrimp had a 4-day lag period. Moreover, the COS and CAP could effectively inhibit the growth of Aliivibrio, the predominant microbial group in the ultimate storage period. This study suggests that the combined utilization of COS and CAP could be a high-efficacy technique for extending the shelf-life of shrimp.

Emulsions containing composite (clove, oregano, and cinnamon) essential oils: Phase inversion preparation, physicochemical properties and antibacterial mechanism.

Natural essential oils (EOs), especially those combining different individual EOs (also termed composite EOs) with enhanced performance, are becoming healthy, market-sought food preservatives/additives. This study aims to provide insights into the challenge regarding EOs processing due to their low solubility and the elusive mechanism under the enhanced bio-reactivity of composite EOs. A unique oil/water interacting network was created by phase-inversion processing, which enhances EO solubilization and emulsification to form composite EO formulations (EOFs) containing ordinary cinnamon, oregano and clove EOs. These EOFs mainly contained cinnamaldehyde, carvacrol and eugenol and exhibited excellent post-storage stability. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability of EOFs (at 15.880 µL/mL) was > 88%, and the Ferric reducing antioxidant power (FRAP) was 1.8 mM FeSO4·7H2O. The minimum inhibitory concentration (MIC) of EOFs against E. coli and S. aureus was ∼7.940 µL/mL. The EOFs could cause quick deterioration of bacterial structures, demonstrating high efficacy in bacteria-killing and anti-biofilm formation.

Oxidative stress induced by plasma-activated water stimulates astaxanthin production in Phaffia rhodozyma.

Astaxanthin is used extensively in the nutraceutical, aquaculture, and cosmetic industries. The current market necessitates higher astaxanthin production from Phaffia rhodozyma (P. rhodozyma) due to its higher cost compared to chemical synthesis. In this study, a bubble discharge reactor was developed to generate plasma-activated water (PAW) to produce PAW-made yeast malt (YM) medium. Due to oxidative stress induced by PAW, strains cultured in 15 and 30 min-treated PAW-made medium produced 7.9 ± 1.2 % and 12.6 ± 1.4 % more carotenoids with 15.5 ± 3.3 % and 22.1 ± 1.3 % more astaxanthin, respectively. Reactive oxygen species (ROS) assay results showed that ROS generated by plasma-water interactions elevated intracellular ROS levels. Proteomic analysis revealed increased expression of proteins involved in the cellular response to oxidative stress as well as carotenoid biosynthesis, both of which contribute to higher yields of astaxanthin. Overall, this study supports the potential of PAW to increase astaxanthin yields for industrial-scale production.