Volume 53, Nº 6 (2017)

The data on features of the hydrolytic cleavage of chitosan by different groups of specific and nonspecific enzymes are summarized. Alternative approaches to the production of chitooligomers and their derivatives are also briefly considered.

Microalgae cultivation for biofuels production and other applications has gained considerable interest recently. Despite their simple structures, microalgae can accumulate significant amounts of neutral lipids per dry cell weight compared to other energy crops. Neochloris oleoabundans is a promising microalga known for its high lipid content and biomass growth rate compared to other species cultivated for biofuels synthesis; therefore, it is considered as a suitable candidate for biodiesel synthesis. This review paper covers several key aspects associated with the cultivation and applications of the microalga N. oleoabundans. Biomass composition, factors affecting the growth, and biomass and lipid productivities of this species were addressed. In addition, different growth conditions as well as alternative readily available nutrient media to support the growth of N. oleoabundans were presented in this review.

Defensins are abundant in cells and tissues that are involved in host defense against microbial infections. zfDB3 (zebrafish β-defensin 3) is one of 3 copies of defensin β-like genes from zebrafish (Danio rerio). Here we focus on mzfDB3, which is the gene encoding for the zebrafish β-defensin 3 mature peptide. A codon-optimized mzfDB3 gene with a 6×His-tag at the 3′-end was inserted into the pPICZαA expression vector and transformed into Pichia pastoris X-33 cells. The recombinant zebrafish β-defensin 3 mature peptide (rmzfDB3) was induced with 1.0% methanol at 29°C for 72 h and purified by immobilized metal affinity chromatography. MALDI-TOF/TOF analysis confirmed the expected purified product (rmzfDB3, 5.9 kDa). Fermentation supernatant, which contained rmzfDB3, showed antibacterial activity against Grampositive (i.e., Listeria monocytogenes, Staphylococcus aureus, and Bacillus cereus) and Gram-negative (i.e., Escherchia coli BL21, Vibrio parahaemolyticus, Salmonella lignieres, and Pseudomonas aeruginosa) bacteria.

Rapeseed proteins were processed by an enzyme complex isolated from king crab hepatopancreas in order to obtain a hydrolysate for use as fish fry feed. The amino acid composition of the obtained protein preparation was close to the amino acid composition of fishmeal traditionally used in the production of fish feed. SDS-PAGE, HPLC, and mass spectrometric analysis of the products of enzymatic hydrolysis of rapeseed proteins showed that the proteins were hydrolyzed to a high degree. The composition of the hydrolysates depended on the hydrolysis time and included free amino acids (27% of the total weight of the protein mix after 3 h of hydrolysis and 56% after 21 h of hydrolysis), short peptides (2 to 20 amino acid residues), and small amounts of protein fragments with a molecular weight of approximately 14 kDa, as shown by by SDS-PAG electrophoresis.

Changes in the activity of Na⁺/K⁺-ATPase and content of membrane lipids (phospholipids) in the gills and hepatopancreas of the blue mussel Mytilus edulis L. have been studied during a sharp temperature increase under aquarian managed conditions. The most pronounced changes were recorded in mollusk gills. A correlation of changes in the activity of membrane-bound Na⁺/K⁺-ATPase and phospholipid content (mainly phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine, and lysophosphatidylcholine) was revealed; this correlation evidences their mutual involvement in compensation for the temperature effect to help mussels adapt to sharp temperature changes.

The effect of potassium sorbate, sodium benzoate, and sodium nitrite used as preservatives in the food industry in the production of such mytotoxins as citrinin cyclopiazonic and mycophenolic acids by the contaminating fungi Penicillium citrinum, P. commune, and P. brevicompactum, respectively, was investigated. It was shown that the effect of preservatives used at concentrations relevant to the food industry on the synthesis of mycotoxins depended on the species-specific biochemical and physiological features of the cultures. The growth of P. brevicompactum was inhibited to the highest degree by sodium nitrite and potassium sorbate, and the growth of P. commune was so inhibited by sodium benzoate. It was established that the introduction of 0.015% sodium nitrite into the medium resulted in 1.3- and 1.4-fold reductions of the production of citrinin and mycophenolic acid, respectively, while the production of cyclopiazonic acid did not change in comparison with the control. The introduction of 0.015% sodium benzoate caused a more than 1.5-fold increase of the concentration of citrinin, cyclopiazonic, and mycophenolic acids, and the addition of 0.02% potassium sorbate increased the production of cyclopiazonic and mycophenolic acids by 1.7 and 2.6 times, respectively.

The effect of hydrogen peroxide treatment on the salt tolerance of wild-type Arabidopsis thaliana L. plants (Col-0) and plants transformed with the bacterial salicylate hydroxylase gene (NahG) was studied. The base tolerance to salt stress caused by 200 mM of NaCl in solution culture was higher in plants with the NahG genotype in comparison with the wild-type plants. Growth inhibition was observed for wild-type plants under the action of exogenous hydrogen peroxide, which was not observed for the NahG transformants; salt tolerance increased in the both types of plants after treatment, which was assessed based on the growth indicators and the ability to preserve the chlorophyll pool following NaCl treatment. The content of endogenous Н2О2 in the leaves of wild-type plants increased significantly following exogenous hydrogen peroxide treatment and salt stress, while it practically did not change in the leaves of the NahG genotype. The SOD activity increased in both genotypes after treatment with exogenous hydrogen peroxide, and remained at an elevated level after salt stress in comparison with the nontreated plants. Furthermore, the catalase activity increased in leaves of the salicylate-deficient genotype but not in the Col-0 genotype. The guaiacol peroxidase activity increased in plants of both genotypes under the action of hydrogen peroxide and salt stress, with the NahG plants demonstrating a higher degree of increase. The Н₂О₂ treatment facilitated the increase of the proline content in leaves of the plants of both genotypes under conditions of salt stress. It was concluded that there were hydrogen peroxide signal transduction pathways in Arabidopsis plants that were salicylic acid independent and that the antioxidant system functioned more effectively in salicylate-deficient Arabidopsis plants.