The process of pit formation in plants still has various questions unaddressed and unknown, which opens up many interesting and new research opportunities. The aim of this work was elucidation of the mechanism for the formation of bordered pits of the spruce (Picea abies (L.) Karst.) tracheid with exosomes participation and mechanical deformation of the cell wall. Sample sections were prepared from spruce stem samples after cryomechanical destruction with liquid nitrogen. The study methods included scanning electron microscopy and enzymatic treatment. Enzymatic treatment of the elements of the bordered pit made it possible to clarify the localization of cellulose and pectin. SEM images of intermediate stages of bordered pit formation in the radial and tangential directions were obtained. An asynchronous mechanism of formation of bordered-pit pairs in tracheids is proposed. The formation of the pit pair begins from the side of the initiator cell and is associated with enzymatic hydrolysis of the secondary cell wall and subsequent mechanical deformation of the primary cell walls. Enzymatic hydrolysis of the S1 layer of the secondary cell wall is carried out by exosome-delivered endoglucanases.

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Microbial dehydrogenase activity can help to determine the oxidizing capacity of activated sludge. Here we propose an innovative and automated express-method based on rapid determination of dehydrogenase activity. The measurement is based on the rate of methylene blue reduction by living microbial cells in suspension. A single analysis takes 10 min. The method was adapted for biofilms immobilized on the floating carriers of industrial bioreactors and the kinetics of biological oxidation by activated sludge and biofilms was compared. New parameters were proposed to characterize the biological oxidation under low oxygen levels. The obtained make it possible to quickly determine the dehydrogenase activity of activated sludge and biofilms and promptly monitor the effectiveness of industrial biological wastewater treatment.

The aim of the present work was to analyze the taxonomic diversity in the Kombucha bacterial consortium during long-term cultivation in the North (Arctic) of the European part of Russia. The high-performance sequencing showed that 99.1 % of the bacterial fraction of the fresh 7-d culture was Proteobacteria of mostly cellulose-producing genera with the order Acetobacterales being dominant and represented by the Komagataeibacter (87.3 %) and Gluconobacter (6.3 %). Aging of the Kombucha bacterial consortium from 20 to 90-d cultivation lead to the reduction of number of cellulose-producing bacteria and intense growth of cellulolytic bacteria including Clostridiales, Bacteroidetes, Actinomyces. Also the acidophilic microorganisms have been detected. The long-term growth of the Kombucha bacterial consortium can be considered as a succession of microbial communities.

This study investigates powdered cellulose materials, particularly nanocellulose derived from plant and bacterial sources. The nanocellulose was generated by hydrolyzing bleached sulphate softwood and hardwood pulp samples with strong acids. The original materials are present in the product lines of leading Russian pulp and paper companies. The bacterial cellulose was produced under laboratory conditions from Medusomyces gisevii. The dimensional parameters of the nanocellulose samples were evaluated using electron microscopy, and the degree of polymerization was measured by determining the viscosity of the cellulose solutions in cadoxene. The bleached softwood pulp had a nanocellulose particle length of 80–200 nm, a particle diameter of 80–100 nm, and a degree of polymerization of 60. The bleached hardwood pulp had a particle length of 80–150 nm, a particle diameter of 70–100 nm, and a degree of polymerization of 50. The bacterial nanocellulose had a particle length of 120–250 nm, a particle diameter of 70–120 nm, and a degree of polymerization of 110. Suspensions of various concentrations (from 1 to 10 %) were prepared from nanocellulose samples, which were subsequently used as reinforcing additives in cardboard samples. The additive was applied to the surface in one or two layers. Additives of nanocellulose preparations reduced the breaking length (from 9.6 to 40.4 %) along with an increase in cardboard density (from 6.3 to 23.8 %), tensile rigidity (from 14.0 to 25.0 %) and bursting strength (up to 31.9 %). The best results were obtained by applying a nanocellulose suspension of bleached softwood pulp to the board surface in two layers: a 9.6 % decrease in breaking length was observed with an increase in density of 23.8 %, tensile rigidity of 25.0 %, and bursting resistance of 31.9 % relative to the control sample. Therefore, the study showed the possibility of using nanocellulose suspensions derived from plants and bacterial sources by acid hydrolysis for the surface treatment of cardboard. For citation: Toptunov Е.А., Sevastyanova Yu.V., Vashukova K.S. Surface Treatment of Cardboard with Plant and Bacterial Derived Nanocellulose Suspensions. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 3, pp. 162–172. (In Russ.). https://doi.org/10.37482/0536-1036-2023-3-162-172

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