Fossil resources-free sustainable development can be achieved through a transition to bioeconomy, an economy based on sustainable biomass-derived food, feed, chemicals, materials, and fuels. However, the transition to bioeconomy requires development of new energy-efficient technologies and processes to manipulate biomass feed stocks and their conversion into useful products, a collective term for which is biorefinery. One of the technological platforms that will enable various pathways of biomass conversion is based on pulsed electric fields applications (PEF). Energy efficiency of PEF treatment is achieved by specific increase of cell membrane permeability, a phenomenon known as membrane electroporation. Here, we review the opportunities that PEF and electroporation provide for the development of sustainable biorefineries. We describe the use of PEF treatment in biomass engineering, drying, deconstruction, extraction of phytochemicals, improvement of fermentations, and biogas production. These applications show the potential of PEF and consequent membrane electroporation to enable the bioeconomy and sustainable development.

Nanosecond pulsed electric field (nsPEF) is a novel modality for permeabilization of membranous structures and intracellular delivery of xenobiotics. We hypothesized that oxidative effects of nsPEF could be a separate primary mechanism responsible for bioeffects. ROS production in cultured cells and media exposed to 300-ns PEF (1–13 kV/cm) was assessed by oxidation of 2′,7′-dichlorodihydrofluoresein (H2DCF), dihidroethidium (DHE), or Amplex Red. When a suspension of H2DCF-loaded cells was subjected to nsPEF, the yield of fluorescent 2′,7′-dichlorofluorescein (DCF) increased proportionally to the pulse number and cell density. DCF emission increased with time after exposure in nsPEF-sensitive Jurkat cells, but remained stable in nsPEF-resistant U937 cells. In cell-free media, nsPEF facilitated the conversion of H2DCF into DCF. This effect was not related to heating and was reduced by catalase, but not by mannitol or superoxide dismutase. Formation of H2O2 in nsPEF-treated media was confirmed by increased oxidation of Amplex Red. ROS increase within individual cells exposed to nsPEF was visualized by oxidation of DHE. We conclude that nsPEF can generate both extracellular (electrochemical) and intracellular ROS, including H2O2 and possibly other species. Therefore, bioeffects of nsPEF are not limited to electropermeabilization; concurrent ROS formation may lead to cell stimulation and/or oxidative cell damage.

Using of pulsed electric fields (PEF) for killing of microorganisms in liquid foods is a promising new nonthermal food processing and preservation technology. However, to implement and optimize this technology, a good understanding of the actual mechanisms that govern microbial inactivation by this technique is required. Here, fundamentals of cell electroporation, which is considered as underlying phenomenon of food processing technology, are discussed. The whole process of the cell electroporation (food processing) by PEF is divided into the following four main stages: (1) building the transmembrane potential up by the applied external electric field, (2) creation of small metastable hydrophilic pores, when the transmembrane potential has been built up; (3) evolution of the pore population-the change in the number and/or sizes of poresduring an electric treatment; and (4) post-treatment stage consisting of the processes that take place after the electric treatment (leakage of intracellular compounds, pore shrinkage and disappearance, etc.). The current knowledge of the processes taking place during each of the above stages as well as the factors influencing them is discussed. Theoretical considerations are illustrated with the experimental data available.

Here, the sizes of the pores created by square-wave electric pulses with the duration of 100 μs and 2 ms are compared for pulses with the amplitudes close to the threshold of electroporation. Experiments were carried out with three types of cells: mouse hepatoma MH-22A cells, Chinese hamster ovary (CHO) cells, and human erythrocytes. In the case of a short pulse (square-wave with the duration of 100 μs or exponential with the time constant of 22 μs), in the large portion (30-60%) of electroporated (permeable to potassium ions) cells, an electric pulse created only the pores, which were smaller than the molecule of bleomycin (molecular mass of 1450 Da, r≈0.8 nm) or sucrose (molecular mass of 342.3 Da, radius-0.44-0.52 nm). In the case of a long 2-ms duration pulse, in almost all cells, which were electroporated, there were the pores larger than the molecules of bleomycin and/or sucrose. Kinetics of pore resealing depended on the pulse duration and was faster after the shorter pulse. After a short 100-μs duration pulse, the disappearance of the pores permeable to bleomycin was completed after 6-7 min at 24-26°C, while after a long 2-ms duration pulse, this process was slower and lasted 15-20 min. Thus, it can be concluded that a short 100-μs duration pulse created smaller pores than the longer 2-ms duration pulse. This could be attributed to the time inadequacy for pores to grow and expand during the pulse, in the case of short pulses.

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