Anna Alekseevna Sukhanova

Background.Golden potato cyst nematode (Globodera rostochiensis, GPCN) is a dangerous quarantine pest of potato, and efficacy of usual nematicides is often limited. One is possible solutions is development of formulations with gradual and controlled release of active ingredients by their encapsulation into biodegradable carriers. Isothiocyanates (ITCs) have been previously shown as effective nematicides. Purpose. The aim of this work was to develop and study granules composed of polycaprolactone (PCL) and bentonite loaded with ITCs (allyl isothiocyanate (AITC), benzyl isothiocyanate (BITC), and 2-phenylethyl isothiocyanate (PEITC)) against GPCN for soil application. Materials and methods. Granules of poly-ε-caprolactone with bentonite containing ITCs as nematicide agents were obtained by extrusion. The encapsulation efficiency of ITCs was determined by chromatography. Efficacy of the granules against GPCN was assessedin vitroby mortality of nematodes and in laboratory soil ecosystem on potato plants of two varieties, ‘Krasnoyarsky Ranniy’ and ‘Innovator’, by yield assessment. Results.In vitroexperiments confirmed the efficacy of PCL/bentonite/isothiocyanate granules in inhibiting the development of second-stage juveniles (J2) of GPCN. The PCL/(PEITC/bentonite) granules achieved 100% nematode mortality within 48 hours, acting 1 to 2 times faster than those containing BITC or AITC. In soil experiments with potato plants, treatment with the PCL/(PEITC/bentonite) granules reduced the number of cysts on roots by 4.2–5.0 times relative to the control; a result was comparable to that of the commercial reference product ‘Vydate® 5G’. Application of the PCL/(PEITC/bentonite) granules enhanced the yield of the ‘Innovator’ potato variety.

PLA- and PHB-based films were plasticized with triacetin (TA), triethyl citrate (TEC), tributyl-o-acetyl citrate (TBAC) in concentrations ranging from 1 to 10 wt.%. We found that introduction of TA and TEC affected the surface of PLA films, leading to the formation of closed pores and cavities, whereas TBAC did not noticeably affect the surface. Upon plasticization, the elongation at break of PLA films increased up to 30-fold. The introduction of plasticizers caused less than a two-fold change in the values for PHB films. The plasticized PLA and PHB films were characterized by lower melting points (around 143–144 °C and 166–167 °C, respectively) compared to the non-plasticized films (147 °C and 168 °C). Following incubation in aqueous model solutions (5% sodium chloride, 2% citric acid, 0.3% lactic acid), the plasticizers gradually migrated from the films into the environment, reaching 0.0034 mg∙mg–1. This migration led to a reduction in the films' mechanical properties: at pH 6.0, the tensile strength and elongation at break decreased by a factor of 1.3–1.5, while at pH 2.6, a fivefold decrease was observed. The shelf life of chicken fillets was extended up to one week without any obvious change in sensory characteristics. The plasticizer was detected in chicken fillets at a very low concentration (approximately 2.1 µg/g) on day 3 but was no longer detectable by day 7 of the experiment.

In this article, the granules based on polycaprolactone (PCL) and bentonite in the ratio of 75/25 and 50/50 were obtained as a promising carrier for long-term release of isothiocyanates (ITC). According to GC-MS and FTIR spectroscopy, it was found that concentration of ITC in granules increases with increase in clay ratio and depends on the ITC species. It is observed that the inclusion of ITC in PCL/bentonite granules increases the persistence of ITCs in the soil for up to 45 days and prevents their premature hydrolysis.

   Objectives. The work set out to describe conditions for the purification of a model fermentation broth for cultivating the lactic acid-containing micromycete Rhizopus oryzae from impurities of inorganic salts using ion-exchange resins under dynamic conditions.   Methods. The solutions collected for analysis were examined using precipitation titration to determine the concentration of chlorides along with a qualitative reaction with Nessler’s reagent to ascertain the presence of ammonium ions. The concentration of lactic acid was evaluated spectrophotometrically using iron(III) chloride. The total nitrogen content was determined by high-temperature catalytic combustion on a Formacs HT TOC/TN Analyzer (Netherlands). The content of trace elements and macroelements in the samples was determined using an iCAP 6300 Duo inductively coupled plasma emission spectrometer (United Kingdom).   Results. Purification of the model broth under the described conditions was carried out by successive filtration through the cation exchanger KU-2-8 in the H-form and subsequently through a mixture of weakly basic A847 and strongly basic AV-17-8 anion exchangers in the OH-form taken in a one-to-one ratio. The breakthrough of impurity ions into the solution was shown to occur after passing 30-fold and 10-fold volumes of the model broth relative to the volume of the cation-exchange and anion-exchange resins, respectively. The dynamic exchange capacity prior to breakthrough was determined as follows: 0.35 mmol-eq/cm³ for the anion-exchange column and 1.61 mmol-eq/cm³ for the cation-exchange column. The following parameters were defined as column regeneration modes: 3-fold excess of 2 M H₂SO₄, 10-fold excess of distilled H₂O for cation exchange; for anion exchange, 3-fold excess of 2 M NaOH and 20-fold excess of H₂O.   Conclusions. The conducted studies showed that purification of the model fermentation broth of Rhizopus oryzae can be successfully implemented using ion-exchange resins. The model fermentation broth passing successively through cation-exchange and anion-exchange columns was shown to be purified from impurities of mineral salts while maintaining the concentration of lactic acid.

Isothiocyanates (ITCs) are substances formed in the result of hydrolysis of glucosinolates and widely found in plants of the cruciferous and Solanaceae families. ITCs are used in agriculture, medicine and the food industry. This article describes the preparation of complexes based on 3 types of ITCs (allyl isothionate (AITC), benzyl isothionate (BITC) and 2-phenylethyl isothiocinate (PEITC)) and their effect on ecologotrophic groups (ETG) of forest soil microorganisms. It has been proved that the deposition of ITC in bentonite contributes to the prolonged release of AITC, BITC, PEITC and reduces the time of their hydrolysis in the soil. Application of free forms of ITC decreased the number of ammonifiers by 2.6 times (when AITC was added), increased the number of nitrogen fixers up by 1.2 times (when BITC was added), and decreased the number of actinomycetes by 21, 1.4 and 1.9 times when AITC, PEITC and BITC were used, respectively. The number of micromycetes increased only when PEITC and BITC were introduced into the soil. The introduction of ITC/bentonite complexes into the soil resulted in a significant decrease in the number of ammonifiers for AITC/bentonite and PEITC/bentonite samples. The introduction of AITC/bentonite complex into the soil increased the number of nitrogen fixers, actinomycetes and micromycetes. The deposition of PEITC and BITC in the bentonite also led to an increase in the number of micromycetes and nitrogen fixers, respectively, which is most likely due to their low concentrations in contrast to free ITC.

Studies on the producers of L-lactic acid are highly relevant at the moment due to the broad scope of its applications. This study was aimed at selecting culture parameters for a milk-derived thermophilic strain of Weizmannia coagulans that is capable of producing L-lactic acid. It was found that the strain productivity depends on the culture temperature, stirring rate, medium pH, used neutralizing agent, and glucose concentration. The culture in flasks and a fermenter revealed that in 56 hours, the strain is capable of producing up to 80.4 g/L of lactic acid at a corresponding average productivity of 1.44 g/(L×h) with a conversion of about 99%. The most optimal parameters to achieve the highest indicators were a temperature of 50 °С, medium pH of 6.5, and a stirring rate of 150 rpm. This strain was shown to be uninhibited by high glucose concentrations; conversely, it exhibited higher productivity at glucose concentrations of 100–120 g/L in the medium. Among the neutralizing agents used for pH adjustment, the Ca(OH)2 agent was selected, which has the least effect on the size of producer cells during fermentation and whose by-products are the least toxic. The obtained results indicate that further studies on the metabolic properties and genetic modification of this strain are required in order to increase productivity, reduce the inhibitory effect of the target product on the metabolism of the producer, and obtain elevated lactic acid titers in a short fermentation time.

   In this study, the characteristics of extruded granules based on biodegradable poly-ε-caprolactone and montmorillonite deposited with allylisothiocyanate and their effect on Globodera rostochiensis RoI were investigated. The prepared granules were characterized using Fourier-transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy. It was shown that encapsulation efficiency of allylisothiocyanate in montmorillonite depends on the conditions of complex preparation and ranges from 0.76 to 29.83%, and in poly-ε-caprolactone/montmorillonite/allylisothiocyanate granules after thermal processing it decreases down to 1.06 %. According to the results of Fourier-transform infrared spectroscopy it was found that allylisothiocyanate inclusion did not result in formation of new chemical bonds, but significantly affected the temperature of poly-ε-caprolactone degradation that decreased from 537 to 472 °С. In comparison with the thermogram of montmorillonite, the weight loss corresponding to dehydration at 100 °С decreased by 2.9 %, which probably means that part of the intramolecular water was replaced by allylisothiocyanate molecules encapsulated in montmorillonite. In the experiment with two potato varieties infested with nematode cysts it was shown that soil treatment with allylisothiocyanate solutions allows to decrease number of cysts of Globodera rostochiensis RoI compared to positive control (non-treated infested potato) in 1.5–3.0 times depending on the variety. Moreover, in contrast to allylisothiocyanate solutions, poly-ε-caprolactone/montmorillonite/allylisothiocyanate granules are more effective that makes them promising for applications in Globodera rostochiensis RoI control.

Oligomers of poly-3-hydroxybutyrate (PHB) were prepared by aminolysis of high molecular weight PHB with ethylenediamine and 1,4-diaminobutane. Polymer-oligomer blends (10, 30, and 50% content of the oligomers) were prepared as films by solution casting. As the content of oligomers increased, a gradual increase in the hydrophilicity of the polymer surface was observed, resulting reflected in the water contact angle decrease from 84° to 72–76°. In addition, a moderate decrease in elongation at break, Young's modulus, and tensile strength for the blends were observed as more oligomer was added to the film. Finally, the viability of NIH-3T3 mouse fibroblasts was higher compared to intact PHB when growing in non-prepared polymer/oligomer mixtures. These findings confirm the benefits of the introduction of a hydrophilic functionalized oligomer into the PHB matrix in terms of improving the biocompatibility of the resulting polymer/oligomer blends.

This work investigates the growth and productivity characteristics of such lactic-acid producing strains, as Lactobacillus delbrueckii subsp. bulgaricus 19-11 (VKPM B-2368), Lactobacillus acidophilus 5 Ds (VKPM B-2846) and Lactococcus lactis subsp. lactis (VKM B-1662) on standard MRS medium using glucose syrup as a carbon substrate. According to the results of batch cultivation of the selected strains in 5L fermenters for 72 h, the productivity was established to decrease in the Lactobacillus delbrueckii subsp. bulgaricus 19-11 > Lactobacillus acidophilus 5 Ds > Lactococcus lactis subsp. lactis series. L. delbrueckii subsp. bulgaricus 19-11 showed the maximum lactic-acid productivity of 1.94 g/(l×h) with a glucose conversion degree of 87%. After cultivation, a slight decrease in the content of nitrogen, potassium and sodium in the culture liquid of the studied strains was observed. In all strains, the content of other macronutrients (phosphorus, calcium, sulphur, magnesium, barium and iron) increased in proportion to the addition of glucose syrup during cultivation, which is directly related to their significant content in its composition. The Lactobacillus delbrueckii subsp. bulgaricus 19-11 and Lactobacillus acidophilus 5 Ds strains produced racemic (DL) lactic acid, whereas Lactococcus lactis subsp. lactis produced lactic acid with a 73% L-isomer content. The use of glucose syrup in biotechnological processes can contribute to the implementation of waste-free production in the respective enterprises.