[Dependence of DNA-polymerase I supersynthesis on the specific growth rate of Escherichia coli CM 5199].
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Culture Media↗
Biomedical subjects
A N Shkidchenko
Publications and source records attributed to A N Shkidchenko.
[Autostabilization of factors limiting the growth of microbial populations in open systems].
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Bacteria↗
[Physiologic-biochemical changes in the yeast Candida tropicalis during cultivation in an autothermostat regime].
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Adaptation, Physiological↗
[Certain aspects of transformation of 21-acetate of the Reichstein substance "S" by the culture of Tieghemella orchidis].
The transformation of acetate from the Reichstein substance "S" by the culture of Tieghemella orchidis was studied upon a single and fractional addition of the substrate. The effect of streptomycin sulphate, Tween-80, ethanol (steroid solvent) and steroid solution on the respiratory activity of the culture was investigated upon a single and fractional addition of the steroid. During transformation the respiratory activity of the culture decreased--by the end of the process (18-20 hours) it fell 2-2.5-fold upon a single addition of the steroid (1 g/l) and by 20% upon a fractional addition of the steroid (2 g/l). In the latter case the respiratory activity dropped step-by-step if the concentration of the steroid was 1.4-1.6 g/l; simultaneously the transformation activity declined.
Acetates↗
[Autoselection in Candida utilis yeasts in a chemostat culture].
Long-term continuous cultivation of Candida utilis in the conditions of chemostat, with the growth rate being limited with phosphates, was accompanied by autoselection. The culture obtained had a higher growth rate and differed by some physiological characteristics from the parent culture. The content of intracellular phosphates varied from 1.9 to 0.55% per dry weight, depending on the concentration of phosphates in the growth medium. At the threshold concentration (0.007 g/litre), phosphates were not virtually utilized by the culture. Specific time of transitional processes depends on the value of interfering effect.
Bacteriological Techniques↗
[Study of the stability association of oil-degrading microorganisms in an open system].
Investigation of the stability of an association of active hydrocarbon-oxidizing microorganisms grown on diesel fuel showed that not all members of the association were competitive in an open flow system. The abundance of some strains considerably decreased during cultivation. One of the strain groups had consistently high cell titers, both in the medium and on a support. This prompts the authors to use these strains as degraders of diesel fuel.
Alcaligenes↗
[Biodegradation of oil products by degrader strains and their associations in liquid media].
The degrading activities of selected bacterial strains and their associations directed towards fuel oil and diesel fuel in liquid media were studied. Two-member associations composed preferably by Rhodococcus and Pseudomonas strains demonstrated the highest degrading efficiencies. No enhancement was achieved when the number of association members was increased to three, four, or five strains. The population stability of any member strain was found to depend on the association composition.
Bacteria↗
[NMR spin-echo study of the lyophilized biomass of Candida utilis yeasts at different growth stages].
Characteristics of the mobile water fraction isolated from some intracellular structures of freeze-dried cells of Candida utilis were studied as a function of the growth phase by the NMR spin-echo method. Part of the mobile water fraction in the log phase decreases down to ten percent of the biomass weight as compared with 2,5-4% in the stationary phase and in the beginning of the lag phases. Mobility of this water is invariable. A considerable decrease of the mobile water fraction is observed in the post-stationary phase too. A decrease of the mobile water fraction correlates with a decrease of the durability of C. utilis cells and is connected probably with some defects in the membrane structure of the cells and their incomplete development in the log phase of the growth.
Candida↗
[Study of petroleum-degrading activity of microflora from the shoreline region of the Caspian Sea].
Soil samples from the shore of Baku Bay (Caspian Sea), were studied. The content of oil products in the samples amounted to 2.7-8.0 wt%. The total counts of microorganisms were 1.8 x 10(6) cells per g soil, which is by two orders of magnitude lower compared to soils free from oil pollution. In addition, the diversity of microflora is considerably narrower. The samples were used to isolate pure cultures of microbial degraders capable of assimilating 24 to 32% of the oil introduced into liquid nutrient medium in six days. It was demonstrated that the fraction composition of residual oil changed and both light and heavy oil fractions were degraded.
Biodegradation, Environmental↗
[Selection of microorganisms capable of degrading petroleum and petroleum products at decreased temperatures].
Of 150 cultures capable of degrading petroleum at +6 degrees C, 40 strains growing in the liquid mineral nutrient medium containing petroleum (2%) as a sole source of carbon were selected. Of them, 13 cultures displaying a petroleum degradation rate exceeding 25% were selected. Abilities of these cultures and their associations to utilize fuel oil and its components--oils and benzene resins--were studied. The culture exhibiting degradation rates of fuel oil, its oils, benzene resins, and petroleum amounting to 17, 26, 10, and 51%, respectively, was selected. This culture can be used for cleanup of petroleum pollution under cold climatic conditions.
Bacteria↗
[Study of the relationship between the free water fraction in dried Candida utilis and the phosphorus content of cells].
The relationship between the free water fraction and the phosphate content in lyophilized yeast cells of Candida utilis was studied. The yeast were cultivated continuously and periodically, their growth rate being limited by phosphates. The decrease in the phosphate pool from 2% to 0.56% was followed by an increase in the fraction of free water by 6.3 times.
Candida↗
[Use of malt extract as a nitrogen source for continuous cultivation of Candida utilis].
The effect of an aqueous extract from malt sprouts on the growth and development of fodder yeast was investigated during their continuous cultivation. The extract can be used as a nitrogen source during continuous cultivation of fodder yeast. It is supposed that the extract contains compounds capable to inhibit yeast growth. The extract should be added to the nutrient medium in the amount of 4 g/l of dry weight.
Candida↗
[Dynamics of consumption and threshold concentration of glucose during the culture of Torulopsis latvica].
The rate of glucose utilization is lower if Torulopsis latvica is grown on a medium with gradual addition of glucose cf. the complete growth medium. The threshold concentration of glucose, causing a decrease of the respiration activity of the culture, increases in the course of the growth of the microbial population. A correlation is established between the growth phases of the microbial population and the threshold concentration of glucose.
Candida↗
[Estimation of the hydrocarbon-oxidizing activity of microorganisms].
A method allowing the microorganisms growing on substrates with a low water solubility (oil, fuel oil, resins, and asphalthenes) to be isolated and counted was developed. An advantage of the method is its ability to estimate the oil-utilizing activity of each strain visually according to the decolorized zones formed during its growth on oil products. The sizes of these zones indicate which oil-degrading strain is most active.
Bacteria↗
[Low-temperature microbial degradation of crude oil products differing in the extent of condensation].
Out of the 30 strains capable of oil degradation at 4-6 degrees C, four were selected by the ability to degrade 40% of the oil substrate present in the growth medium: Rhodococcus spp. DS-07 and DS-21 and Pseudomonas spp. DS-09 and DS-22. We studied the activity of these strains as degraders of oil products of various condensation degrees (crude oil, masut, petroleum oils, benzene resins and ethanol-benzene resins) at 4-6 degrees C. The maximum degrees of degradation of masut and ethanol-benzene resins were observed in Pseudomonas spp. DS-22 (17.2% and 5.2%, respectively). The maximum degradation of petroleum oils and benzene resins was observed in Rhodococcus spp. DS-07 (40% and 16.6%, respectively). The strains provide a basis for developing biodegrader preparations applicable to bioremediation of oil-polluted sites under the conditions of cold climate.
Benzene↗
[Correlation between the cellular content of mobile water and the viability of lyophilized yeast cells].
Spin-echo NMR studies showed that lyophilized yeast cells contain isolated mobile water (IMW), whose content varied from 0.25% (of the dry weight of cells) in the lyophilized exponential-phase yeast cells to 3.8% in the lyophilized lag-phase and stationary-phase yeast cells. The viability rate of yeast cells varied from 20% in the lyophilized preparation of exponential-phase cells to 86% in the lyophilized preparation of early-stationary-phase cells. In the lyophilized preparation of yeast cells grown in a chemostat mode at a constant specific rate, the content of IMW depended on the growth-limiting factor, being minimal in the case of growth limitation by carbon source. In the latter case, the viability rate of cells was also minimal. The data obtained show that there is a correlation between the IMW content and the viability rate of yeast cells in lyophilized preparations.
Candida↗
[Physiological aspects of intensifying yeast growth].
The possibilities of intensifying yeast growth during flow cultivation via an increase in the rate of medium flow and the concentration of carbon-containing substrate are considered. It is found that stabilization of optimum specific substrate loads provides maximum economic coefficient of the process. Stabilization of optimum specific loads of carbon-containing substrates during a three-stage flow cultivation of yeasts in a medium with n-alkanes allowed the throughput of a battery of fermenters to be elevated 1.84-fold. Alternation of flow chemostatic and turbidostatic yeast cultures was accompanied by a fivefold increase in the maximum specific growth rate.
Bioreactors↗
[Effect of excess ethanol on the growth of yeasts of the genus Candida during continuous cultivation].
The effect of flow rates and a specific ethanol load on the growth of Candida utilis and Candida krusei was studied in the process of one-step and three-step cultivation. The productive capacity of fermenters and the economic coefficient of yeast biomass production were shown to depend on the ability of microbial populations to assimilate a certain quantity of a carbon substrate per unit time. When a specific ethanol load exceeds the optimal one, the respiratory activity of a population and the economic coefficient of growth fall down whereas the accumulation of metabolites in the cultural broth increases. The steady state of biomass can be maintained in the process of continuous cultivation by inhibiting the yeast growth with an excess of ethanol.
Candida↗