A strategy for construction of industrial strains of distiller's yeast.

A procedure was developed for construction of industrial strains of distiller's yeast (Saccharomyces cerevisiae). It includes several steps: construction of congenic genetically marked haploid strains of opposite mating types starting from an industrial strain of hybrid nature, integrative transformation of the above haploid strains with a DNA fragment containing an expression cassette responsible for new technological facilities, and hybridization of transformants and isolation of final industrial homozygous strains under experimental conditions simulating commercial fermentation processes. This strategy permits the generation of strains that have desirable characteristics of traditional races of distiller's yeast along with new technological facilities determined by the particular expression cassette. Using this procedure, we have constructed an industrial strain with improved amylolytic activity. (c) 1995 John Wiley & Sons, Inc.

[Use of rifampicin for directed modification of the nucleotide composition of the cells of Bacillus megaterium and Candida utilis]. / Primenenie rifampitsina dlia napravlennogo izmeneniia nukleotidnogo sostava kletok Bacillus megaterium i Candida utilis.

The object of this work was to study the effect of rifampicin on the physiological state of Bacillus megaterium and Candida utilis in chemostat and batch cultures. When B. megaterium is cultivated in a medium containing 1 microgram of rifampicin per litre, its metabolism changes, the pool of free nucleotides rises, and the content of RNA drops in response to the specific action of the inhibitor. The modified state is observed throughout many generations. The action of the inhibitor is also non-specific: protein content falls and polyhydroxybutyric acid is accumulated. The morphology of B. megaterium cells changes: they become larger, their cell wall thickens, and the separation of cells from one another is complicated. At a high concentration (5 mg/l), rifampicin decelerates the growth of C. utilis and causes merely a minor non-specific inhibition.

[Nonspecific stress in Candida utilis under growth inhibition by a specific inhibitor]. / Nespetsificheskii stress u Candida utilis pri ingibirovanii rosta spetsificheskim ingibitorom.

The physiological state of Candida utilis chemostat cultures was studied when the growth was limited with glycerol at D from 0.047 to 0.35 hr-1, and compared with the same cultures inhibited with cycloheximide. This compound at a concentration of 1 mg/litre almost did not inhibit the growth, but the value of the growth yield decreased from 0.45 to 0.38; the content of protein fell, on the average, from 44 to 35% of the dry biomass weight; the content of polysaccharides increased from 22 to 30%; the content of nucleic acids and lipids did not change; the liberation of keto and amino acids into the medium slightly increased. The population became heterogeneous, the cells increased in size, the separation of daughter cells from the parent ones became complicated, and the number of vacuoles in the cells increased. All of these changes, apart from a significant decrease in the content of protein, are also typical of the action of various nonspecific growth inhibitors.

[Changes in the physiologic properties of a chemostat culture of Propionibacterium shermanii during growth limitation by a deficiency of sodium lactate]. / Izmenenie fiziologicheskikh svoistv khemostatnoi kul'tury Propionibacterium shermanii pri limitatsii rosta nedostatkom laktata natriia.

A chemostat curve has been constructed for changes in the Propionibacterium shermanii population density with an increase in the flow rate of the medium from 0.04 to 0.55 h-1 upon limitation of the growth with sodium lactate deficiency. The curve differs from the classic chemostat curve described with the Monod equation, thus indicating changes in metabolism at different growth rates. Fermentation of lactate to acetic and propionic acids by the culture is most complete at low flow rates of the medium (D = 0.04 h-1). The rates of oxidation processes increase at average flow rates (D = 0.1--0.33 h-1). Lactate is both fermented to yield volatile acids, and oxidized. The growth rate D = mu = 0.55 h-1 approaches the maximal one. The rate of fermentation by the culture at this growth rate decreases while the rate of oxidation increases. The ratio between the rates of these two processes shifts towards oxidation. The cells display now a very high synthetic activity: constructive metabolism of the cells is realized practically only at the account of the nitrogen from ammonium rather than the nitrogen of amino acids. The chemical composition of the cells along the chemostat curve is relatively constant. The content of protein and DNA does not change; the content of RNA slightly rises with an increase in the growth rate, and the protein synthesizing activity of RNA is directly proportional to D = mu.

[Growth of a Propionibacterium shermanii culture under varying aeration conditions]. / Rost kul'tury Propionibacterium shermanii pri razlichnykh usloviiakh aératsii.

The effect of aeration of growth of Propionibacterium shermanii BKM B-103 was studied. Aeration was found to stimulate growth of the culture in a complex medium containing sodium lactate as a source of carbon and energy. When the concentration of oxygen in the medium was raised, the economic coefficient increased, the Ks value for lactate assimilation decreased, and the value of mum did not change.

[Balanced and unbalanced growth of periodic and continuous cultures of Candida utilis]. / Sbalansirovannyu i nesbalansirovannyi rost periodicheskoi i nepreryvnoi kul'tury Candida utilis.

The paper presents mathematically treated data published in literature about the specific growth rate mu and the economic coefficient Y in Candida utilis at the exponential growth phase, at the transient state in chemical from the limitation of growth with a source of carbon and energy to the inhibition with low pH values, and at the stationary state in chemostat. Both parameters show attenuated oscillations in the first two cases, but are constant in the third case. The oscillations of mu and Y are synchronous and their interrelationship is directly proportional. The values of Y may be negative since the cell weight can decrease though the cell still assimilates the substrate. The specific rate of substrate assimilation in oscillations remains constant. Proteins can by synthesized at two different rates while the growth rate is one and the same.

[Transitional state of Candida utilis chemostat culture after shock caused by a low pH value of the medium during 1 generation]. / Perekhodnoe sostoianie khemostatnoi kul'tury Candida utilis posle shoka nizkim znacheniem pH sredy v techenie odnoi generatsii

Transitional states of Candida utilis BKM Y-1668 were found during its growth in conditions of chemostat at D of 0.1 hr(-1) and glycerol limit after a shock caused by an extreme pH value (2.2). The optical density of the cells, the amount of dry biomass and protein, the activity of respiration, the content of ATP, and the activity of ATPase decreased, the character of the decrease being that of damped oscillations. Qualitative changes were detected in the activity of respiration, oxygen uptake was not inhibited by cyanide. More glycerol and phosphorus are utilized in processes of vital activity. Therefore, a sharp change of pH values causes profound changes in the metabolism of the yeast cell.

[Effect of low pH values on the chemical composition of a chemostat culture of Bacillus megaterium]. / Vliianie nizkogo znacheniia pH na khimicheskii sostav khemostatnoi kul'tury

Inhibition of the growth of Bacillus megaterium was studied in the conditions of chemostat. Inhibition of the growth by hydrogen ions had almost no effect on the content of DNA, RNA, protein and polysaccharides, but the protein-synthesizing activity of RNA changed. The content of polyphosphates, of high and low molecular weight, depended on pH; the relationship was of a non-linear character. The total content of lipids increased with the concentration of hydrogen ions.