Polysaccharide processing by means of low-temperature Electron Beam Plasma (EBP) is a promising alternative to the time-consuming and environmentally hazardous chemical hydrolysis in oligosaccharide production. The present paper considers mechanisms of the EBP-stimulated destruction of crab shell chitin, cellulose sulfate, and microcrystalline cellulose, as well as characterization of the produced oligosaccharides. The polysaccharide powders were treated in oxygen EBP for 1–20 min at 40 °C in a mixing reactor placed in the zone of the EBP generation. The chemical structure and molecular mass of the oligosaccharides were analyzed by size exclusion and the reversed phase chromatography, FTIR-spectroscopy, XRD-, and NMR-techniques. The EBP action on original polysaccharides reduces their crystallinity index and polymerization degree. Water-soluble products with lower molecular weight chitooligosaccharides (weight-average molecular mass, M_w = 1000–2000 Da and polydispersity index 2.2) and cellulose oligosaccharides with polymerization degrees 3–10 were obtained. The ¹H-NMR analysis revealed 25–40% deacetylation of the EBP-treated chitin and FTIR-spectroscopy detected an increase of carbonyl- and carboxyl-groups in the oligosaccharides produced. Possible reactions of β-1,4-glycosidic bonds’ destruction due to active oxygen species and high-energy electrons are given.

Applications of nonequilibrium low-temperature oxygen electron-beam plasma (EBP) for the controllable processing of biopolymers (crab shell chitosan and softwood lignocellulose) are described. Water-soluble chitooligosaccharides with weight-average molecular mass Mw = 800-2000 Da and polymerization degree varying from dimers to heptamers were obtained after the EBP-stimulated chitosan destruction; trimers being the most predominant. Water solutions of the EBP-produced chitosan oligomers enhanced the seeds germination and stimulated green mass formation in barley Hordeum vulgare. The EBP processing of lignocellulose resulted in its amorphization and formation of additional oxygen containing functional groups at the surface of the biomaterial.

Design of a hybrid plasma-chemical reactor in which strongly non-equilibrium low-temperature plasma is generated by joint action of a continuous electron beam and RF-gas discharge on gaseous media at moderate pressures (0.1–10 Torr) is described. Several versions of the reactor in a co-axial configuration were tested on the special experimental setup. Main characteristics of the reaction zone were studied as functions of electron beam and gas discharge parameters, plasma-generating media properties and peculiarities of the working process features. Temperature regimes of the materials processing were reliably controlled by the electron beam parameters. The reactor was applied to thin films and dispersed powders of natural polysaccharides (chitosan) and biomaterials (wood) processing to produce valuable low-molecular and bioactive compounds. In hybrid plasma of oxygen, the active particles responsible for the materials modification effects are atomic oxygen, ozone and singlet oxygen. Special software simulating the reactor operation and material treatment processes in plasmas of oxygen was developed and experimentally verified.

A novel technique of phytoactive water-soluble chitooligosaccharide (COS) production in low-temperature plasma is described. Design, operation, and control of plasma chemical reactors used to produce COS from the powder of high molecular weight chitosan are presented. The electron beam plasma is strongly non-equilibrium and chemically active; plasma was excited by injecting the scanning electron beam into reaction volume filled with aerosol, containing oxygen and chitosan powder. Plasma chemical processes, responsible for the raw chitosan destruction and techniques of these processes to obtain control of products of optimal molecular weight, are considered. COS, in amounts sufficient for laboratory tests with some plants, were produced. Tests showed that the addition of COS into the liquid growing medium at 0.25 and 1 mg/mL stimulates root growth in Arabidopsis thaliana seedlings (Col-0) by up to 40%, with respect to control plants. Foliar application of these COS formulations at 0.25 mg/mL on tomato plants (cv. Micro-Tom) also resulted in increases between 11.9% and 36% in two important plant productivity indicators (flower and fruit numbers) compared to the control plants. Being environmentally friendly (and resource saving) the electron beam plasma technology of renewable natural biopolymer processing can be considered as a competitive way to produce biostimulants for commercial agriculture.