[The effect of pH, aeration, and temperature on arachidonic acid synthesis by Mortierella alpina].

The effects of pH, aeration, and temperature on the growth of fungal strain Mortierella alpina LPM-301 and the synthesis of lipids and arachidonic acid in glycerol-containing medium were studied. Arachidonic acid production in the stationary growth phase was found to depend considerably on the pH value; it reached the optimum at pH 6.0 and was irreversibly inhibited at a pH of 3.

The stoichiometry and energetics of oxygenic phototrophic growth.

The values of gross metabolic flows in cells are essentially interconnected due to conservation laws of chemical elements and interrelations of biochemical coupling. Therefore, the overall stoichiometry of cellular metabolism, such as the biomass quantum yield, the ratio between linear and circular flows via the electron transport chain, etc., can be calculated using balances of metabolic flows in the network branching points and coupling ratios related to ATP formation and expenditures.

The effect of lipid content on the elemental composition and energy capacity of yeast biomass.

Oleaginous yeasts (18 strains) were grown in ethanol media under various cultivation conditions (33 biomass samples). It was found that lipid and lipid-free fractions of dry biomass have elemental composition and biomass reductivity very close to values which can be considered as biological constants. The energy content of dry biomass strongly depended on the total lipid content.

The problem of the eukaryotic genome size.

The current state of knowledge concerning the unsolved problem of the huge interspecific eukaryotic genome size variations not correlating with the species phenotypic complexity (C-value enigma also known as C-value paradox) is reviewed. Characteristic features of eukaryotic genome structure and molecular mechanisms that are the basis of genome size changes are examined in connection with the C-value enigma. It is emphasized that endogenous mutagens, including reactive oxygen species, create a constant nuclear environment where any genome evolves.

EDTA-dependent assimilation of glucose and organic acids by an EDTA-degrading bacterium.

Bacterial strain VKM B-2445 is characterized by ethylenediaminetetraacetate (EDTA) requirement for cell growth. This strain could not grow on glucose and organic acids as the sole sources of carbon and energy, but it was able to metabolize these substrates added to EDTA medium. EDTA initiated assimilation of glucose, succinate, fumarate, malate, and citrate and supplied nitrogen for the biomass production from these substrates.

[Genomic noncoding sequences and the size of eukaryotic cell nucleus as important factors of gene protection from chemical mutagens].

An improved quantitative model describing a protective function of eukaryotic genomic noncoding sequences was developed. In this new model, two factors affecting gene protection from chemical mutagens are considered: (1) the ratio of the total lengths of coding and noncoding genomic sequences and (2) the volume of the cell nucleus. An increase in the noncoding DNA in the genome reduces the number of mutagen-damaged nucleotides in the coding region, whereas an increase in the volume of the nucleus decreases the flow of mutagens per unit of nuclear volume that attacks its surface.

[Synthesis of bacteriochlorophyll a by the purple nonsulfur bacterium Rhodobacter capsulatus].

The ability of purple nonsulfur bacteria Rhodobacter capsulatus B10 to synthesize bacteriochlorophyll under phototrophic and dark conditions was studied. The modes for cultivation in the dark with oxygen limitation in a continuous culture at D = 0.1 h(-1) were selected.

[Noncoding sequences of the eukaryotic genome as an additional protection of genes from chemical mutagens].

A quantitative model was developed that detects a new function of noncoding sequences in the eukaryotic genome, namely, the protection of coding sequences from chemical (mainly endogenous) mutagens. It was shown that, under common ecological conditions, the number of nucleotides damaged by mutagens in coding sequences of the genome is inversely proportional to the size of their noncoding counterparts. Noncoding sequences can differently protect single genetic loci from chemical mutagens by the formation of specific spatial structures of the protected loci in the interphase nuclei.

[Bacterial degradation of EDTA].

Degradation of EDTA (ethylenediaminetetraacetic acid) or metal-EDTA complexes by cell suspensions of the bacterial strain DSM 9103 was studied. The activity of EDTA degradation was the highest in the phase of active cell growth and decreased considerably in the stationary phase, after substrate depletion in the medium. Exponential-phase cells were incubated in HEPES buffer (pH 7.

[Mass-energy balance of the growth of phototropic purple bacteria].

The principles of the theory of mass-energy balance of the growth of cellular populations are described. Based on this theory, the effect of biochemical parameters of cell metabolism on the efficiency of phototrophic growth of bacterial culture was studied. The metabolism of phototrophic bacteria was subdivided into constructive and energetic partial metabolisms.

Application of mass and energy balance regularities in fermentation. Reprinted from Biotechnology and Bioengineering, Vol. XX, No. 10, Pages 1595-1621 (1978).

Material and energy balances for fermentation processes are developed based on the facts that the heat of reaction per electron transferred to oxygen for a wide variety of organic molecules, the number of available electrons per carbon atom in biomass, and the weight fraction carbon in biomass are relatively constant. Mass-energy balance equations are developed which relate the biomass energetic yield coefficient to sets of variables which may be determined experimentally. Organic substrate consumption, biomass production, oxygen consumption, carbon dioxide production, heat evolution, and nitrogen consumption are considered as measured variables.

Continuous growth of Candida utilis under periodic change of growth-limiting substrate.

A periodic change of limitation by glucose and ammonia was effected during continuous cultivation of Candida utilis. Values of feed parameters providing periodic nitrogen limitation were established. Cell biomass yield, macromolecular composition and parameters of individual cells (cell mass, budding percentage and cell-wall polysaccharide per surface square unit) were examined.

Bistat--a novel method of continuous cultivation.

Bistat is the method of continuous cultivation developed on the basis of pH-auxostat. It provides the stability of cultivation in each point of mu(S) dependence. This article describes the principle of bistat operation, the theory of bistat dynamics, its instrumentation, and some experimental results.

Estimation of available efficiency of microbial growth on methanol and ethanol.

The balances of reductivity and high-energy bonds (HEB) during microbial growth on glucose (a standard substrate), methanol, and ethanol are reported. Also, numerical values for the quantities of HEB formation in the respiratory metabolism, HEB consumption in the constructive metabolism, as well as in a number of the other intracellular processes are evaluated. Estimations of maximum cell yields by mass and energy are made during growth on methanol and ethanol with regard to peculiar features of different microbe metabolism.

Mass-energy balance for microbial product synthesis-biochemical and cultural aspects.

Interrelations between the rates of the product synthesis, cell biomass growth, respiration, and organic substrate consumption have been studied by the mass-energy balance method. This method is based on the utilization of a special unit of substance reducity, namely redoxon. Biochemical parameters have been found which are involved in these interrelations and which describe the processes of high-energy bond gain and energy expenditure during metabolism.

[Relationship between energetics and reduction level of organic substances as an important factor in metabolic energy balance].

The reduction level of any chemical compounds is measured by special units--redoxones. In organic compounds the energetic value of redoxon is almost constant. Application of this concept makes it possible to simplify considerably the energetic calculations in biochemistry and to develop a common approach considering metabolism as the transfer of redoxons along the reactions network from the initial source of the redoxons to the biomass substance.

[Effect of cell metabolism on the rate of medium addition during pH stabilized cultivation].

The rate of base or acid addition to the culture broth for maintenance of the present pH-value is a quantity reflecting the metabolic activity of the cell population. This quantity is proportional to the biomass growth rate with the proportionality coefficient depending on the cell consumption of ionized substrates from the environment, cell biomass, electric charge, and content of ionized metabolic products in the medium. The equation for this relationship has been found and the effect of the above, factors on the titration rate has been calculated.

[Ionic balance during cultivation of cell populations in a spatially homogeneous medium].

In culture medium many ionic reactions proceed. Extracellular substances and the cell proper participate in these reactions. For the analysis of ionic processes proceeding in this system the classical approach of physical chemistry is broadened, the effect of flow and cells being taken into account.

[Growth efficiency and the specific rate of the yeast Hansenula polymorpha during continuous cultivation on methanol].

The growth of Hansenula polymorpha DL-1 in the chemostat (under methanol limitation) and turbidostat was measured. Cultivation with different specific rates of growth mu made it possible to determine the maximum yield of biomass Ys(max)=0.425 and the level of expendables required to maintain Ms=0.

Dependence of cell yield and specific growth rate of Candida boidinii on temperature during continuous cultivation.

Investigation of the dependence of cell yield of Candida boidinii in a chemostat and specific growth rate in a turbidostat on temperature was carried out using methanol as substrate. Each of the curves obtained had only one maximum, the optimum temperature for yield (Ys) and for specific growth rate (micron) being somewhat different. With deviation of temperature from the corresponding optimum the micron value decreases more sharply than that of Ys.