Experimental study of some Siberian and Baikal endemic species of hydrobionts: Comparative analysis of oxyphility and frigophility

Adaptive features of some hydrobionts of the Baikal and Siberian faunas have been studied. It is revealed that the studied groups of invertebrates living in near-Baikal water bodies and streams are less stable to the action of some abiotic factors than representatives of the Baikal endemic fauna. Some of the hypotheses proposed to explain the “immiscibility” of Baikal endemics and Siberian ubiquists are questioned.     

Characteristics of Cyclodextrin Production Using Cyclodextrin Glucanotransferases from Various Groups of Microorganisms

Cyclodextrin glucanotransferases (CGTases; EC 2.4.1.19) from newly isolated mesophilic, thermophilic, alkalophilic, and halophilic bacilli, as well as from thermoactinomycetes, were purified to homogeneity, and some of their physicochemical and biochemical characteristics (cyclizing, disproportionating, and hydrolytic activities) were studied. Cyclodextrin (CD) production in the presence and absence of compounds favoring formation of complexes had certain specific features. We were able to demonstrate that CGTases of mesophilic and thermophilic strains form mixtures of -, -, and -CDs, whereas the enzymes from halophilic and alkalophilic microorganisms preferentially catalyze the formation of -CD.     

Combined use of eBeam irradiation and the potential probiotic Lactobacillus rhamnosus Vahe for control of foodborne pathogen Klebsiella pneumoniae

The implementation of electron beam radiation coupled with the use of probiotics is one of the newest food processing technologies that may be used to ensure food safety and improve shelf life of food products. The purpose of this study was to evaluate the effect of 50–150-Gy electron beam irradiation on the antimicrobial activity of the putative probiotic strain Lactobacillus rhamnosus Vahe. Low-dose electron beam irradiation of lactobacilli cells was performed using the Advanced Research Electron Accelerator Laboratory’s electron accelerator, and the agar well diffusion method and Verhulst logistic function were used to evaluate the effect of radiation on anti–Klebsiella pneumoniae activity of the cell free supernatant of L. rhamnosus Vahe cells in vitro. Our results suggest that 50–150-Gy electron beam irradiation decreases the viability of the investigated lactobacilli, but does not significantly change the probiotic’s activity against K. pneumoniae. Results indicate that the combined use of irradiation and L. rhamnosus Vahe might be suggested for non-thermal food sterilizing technologies.     

Light avoidance in Baikalian amphipods as a test response to toxicants

The dependence between the time of escape of Eulimnogammarus vittatus from light and toxicants in the medium has been studied. It has been shown that these amphipods display the most rapid response to light in pure Baikal water. Toxicants slow down the movement of E. vittatus in the dark. A similar effect has been observed during the experiments with heavy metals, detergents, and petroleum products. The results indicate a good prospect for using this reaction as a test response during the biological assay of toxic contamination with the help of E. vittatus.     

Transglycosylation of Stevioside by Cyclodextrin Glucanotransferases of Various Groups of Microorganisms

Cyclodextrin glucanotransferases (CGTases, EC 2.4.1.19) produced by mesophilic, thermophilic, alkaliphilic, and halophilic bacilli were used for transglycosylating stevioside (in order to remove bitterness and aftertaste), with cyclodextrins (CDs) being used as donors. It was shown that CGTases produced by extremophilic microorganisms are effective biocatalysts. Optimum temperature and pH of these enzymes were 45°C and pH 6.5–7.5, respectively. The optimum stevioside-to-CD ratio and total concentration of dry matter for the synthesis of the best-tasting product were 1 : 1 (w/w) and 11.6%, respectively.     

Some growth peculiarities and membrane characteristics of probiotic strains of Escherichia coli

It is found that the probiotic strains of Escherichia coli, G35 N 59 isolated from “Okarin” and from “ASAP” drug formulas, and the commensal strain 5–1 isolated from healthy human intestine, manifest higher specific growth rates, lower acidifying capacity during glucose fermentation in the external medium, and lower rates of decrease in redox potential in comparison with the wild-type strain (MC4100). At the same time, despite similar values of their membrane potentials, these bacteria differ essentially in total and N,N′-dicyclohexylcarbodiimide-sensitive rates of energy-dependent transmembrane H⁺ and K⁺ transport and display a low level of H₂ production. It is suggested that the difference between their membrane characteristics reflects changes in the activity of proton-translocating F₀F₁-ATPase and is crucial for bacterial growth and probiotic activity of E. coli.