Maximum Growth Yield Research Articles

Isolation and characterization of a thermotolerant methanol-utilizing yeast.

A yeast capable of growth on methanol as its sole carbon-energy source was isoalted from soil samples and identified as a strain of Hansenula polymorpha. A continuous enrichment culture at 37 C with a simple mineral salts medium was used to select this organism. The isolate, designated DL-1, has a maximal specific growth rate of 0.22 per h, at pH 4.5 to 5.5 and temperatures of 37 to 42 C, in simple mineral salts medium with methanol (0.5%), biotin, and thiamine. Growth occurred in a chemostat at temperatures up to 50 C, with strong growth at 45 C. The maximal growth yield of the yeast on methanol was 0.36 g of dry cell weight per g of methanol, and the yield on oxygen was 0.37 g of dry cell weight per g of O(2). Protein content of the isolate is 46%, and total nucleic acid content varies from 5.0 to 7.0% with increasing growth rate from 0.08 to 0.20 per h. The amino acid profile of this yeast protein indicates that it could serve as a good source of food protein. Feeding studies with rats show the yeast to have no toxic effects.

Isolation and Characterization of a Thermotolerant Methanol-Utilizing Yeast

A yeast capable of growth on methanol as its sole carbon-energy source was isoalted from soil samples and identified as a strain of Hansenula polymorpha. A continuous enrichment culture at 37 C with a simple mineral salts medium was used to select this organism. The isolate, designated DL-1, has a maximal specific growth rate of 0.22 per h, at pH 4.5 to 5.5 and temperatures of 37 to 42 C, in simple mineral salts medium with methanol (0.5%), biotin, and thiamine. Growth occurred in a chemostat at temperatures up to 50 C, with strong growth at 45 C. The maximal growth yield of the yeast on methanol was 0.36 g of dry cell weight per g of methanol, and the yield on oxygen was 0.37 g of dry cell weight per g of O(2). Protein content of the isolate is 46%, and total nucleic acid content varies from 5.0 to 7.0% with increasing growth rate from 0.08 to 0.20 per h. The amino acid profile of this yeast protein indicates that it could serve as a good source of food protein. Feeding studies with rats show the yeast to have no toxic effects.

The effect of temperature on spore germination and growth of Mucor miehei in submerged culture.

Mucor miehei was grown in submerged culture at 30, 37, 40, 42.5, 45, and 48 °C. Maximum growth yield occurred at 48 °C.The effect of temperature on spore germination was examined. No spores germinated within 8 h at temperatures below 36.7 °C or above 53.5 °C. The optimum temperature for spore germination was 45 °C.Growth occurred at the marginal temperatures of 20 °C and 25 °C only when the spores were pre-germinated at 37 °C

ATP Pool and Growth Yield in Selenomonas ruminantium

SUMMARY: The ATP pool in Selenomonas ruminantium growing in continuous culture under carbohydrate-limited conditions was low (averaging 2.3 nmoles/mg dry wt bacteria) and appeared independent of growth rate over the range of optimum growth. The high maximum growth yield (Y gluc62) previously found for another strain of selenomonad was confirmed and growth on glucose plus pyruvate gave a calculated value for Y pyr of about 21. A tentative scheme is suggested for production of ATP from electron-transfer reactions which would make the value for Y ATP for high growth-yield rumen anaerobic bacteria nearer to the accepted value of 10 than the values found using previously suggested modes of ATP formation.

Extended culture: the growth of Candida utilis at controlled acetate concentrations.

AbstractExtended culture, a special type of semicontinuous culture, permits prolonged maintenance of a constant or programmed environment in a growing culture by a controlled addition of one or more substrates. Differences between extended culture and continuous culture data are a measure of differences in the properties of cell populations with different cell age distributions but identical steady‐state environments. Both extended culture and continuous culture were used to study the growth kinetics of Candida utilis (ATCC 9226) under conditions of substrate inhibition at controlled concentrations of sodium acetate in a carbon‐limited mineral salts medium supplemented with 0.01 g/1 yeast extract. Acetate concentrations ranged from 1.2 g/l to 10.8 g/l (expressed as acetic acid), while yeast concentrations varied from 0.3 to 7.8 (g dry cells)/1. Rate parameters such as growth yields (Y), specific growth rates (μ), and linear growth rates (K), were calculated by computer from the data and theory presented herein. Specific growth rates as high as 0.54/hr were observed, although extended culture growth was more nearly linear than exponential in these experiments. Growth yields usually varied between 0.2 and 0.4 (g dry cells)/(g acetate), although values were as high as 0.8 for a brief period during one experiment. Growth yields at a given acetate concentration were correlated by an equation of the form 1/Y = 1/YG + m/μ. A maintenance coefficient (m) of 0.17 (g acetate)/(g dry cell‐hr) was observed at acetate concentrations of 4.5 and 10. g/1. A typical maximum growth yield (YG) of 0.51 (g dry cell)/(g acetate) was obtained at 4.5 g/1 acetate, but an unusually high YG of 1.33 was found at 10. g/1 acetate. Oxygen uptake measurements are compared with these cell yield measurements. Linear growth rates in expended culture were correlated by the equation K = 0.89–0.70 (S/S0) where K has units of (g dry cell)/(l‐hr), S is the instantaneous acetate concentration, and S0 is the initial acetate concentration. The extended culture kinetic data are shown to be substantially different from continuous culture kinetic data. Reason for these differences are discussed in light of diffrences in the cell age distributions, as well as possible differences in experimental conditions.

The effect of temperature on the metabolism of baker's yeast growing on continuous culture.

SUMMARY: Glucose-limited cultures of baker's yeast growing at 25° had a maximum growth rate, saturation constant and yield constant of 0.22 hr−1, 129 μg./ml. and 0.225, respectively, whereas when growing at 38° the corresponding values were 0.25 hr−1, 300 μg./ml. and 0.204. In continuous culture, with the dilution rate fixed at 0.1 hr−1 there were no differences observed in viability, incidence of respiratory deficient mutants, cytochrome spectra or mean cell dry weights, between cultures grown at 25 and 38°. The culture grown at 25° had a smaller mean cell volume, greater yield value and nitrogen utilization. Ethanol, pyruvate and α-ketoglutarate were secreted to a greater degree in cultures grown at 38°. Yeast grown at 25° had a smaller capacity to produce carbon dioxide but greater ability to take up oxygen. Enzymes associated with glycolysis, alcohol production, tricarboxylic acid cycle and respiratory chain in organisms cultured continuously at 25 and 38° showed few important differences. The most obvious ones were those involving α-ketoglutarate as a substrate, especially α-ketoglutarate dehydrogenase. There were only small differences in adenosine phosphates and nicotinamide nucleotides. At 25° the ratio NAD/NADH was 1.5 but for organisms grown at 38° the ratio was 1.1.

Yield coefficients of Thiobacillus neapolitanus in continuous culture.

Thiobacillus neapolitanus, when grown in continuous culture with thiosulfate limiting growth, possessed an apparent maximal molar growth yield of 8.0 g (dry weight) per mole of thiosulfate. The substrate requirement for energy of maintenance was the highest yet reported, amounting to 21.8 mmoles of thiosulfate per g per hr. The molar growth yield, corrected for this maintenance energy requirement, was 13.9 g (dry weight) per mole of thiosulfate. It was concluded that substrate-level phosphorylation during sulfite oxidation accounted for about 45% of the adenosine triphosphate (ATP) requirement for CO(2) assimilation and maintenance during growth on limiting thiosulfate, that three sites of energy conservation exist in the electron-transport chain terminating in oxygen, and that 7.8 moles of ATP are required to fix and assimilate 1 mole of CO(2) into cell material.

Factors influencing the fermentation and growth of an atypical strain of Actinomyces naeslundii.

An atypical strain of Actinomyces naeslundii (A.T.C.C. 10049) has been studied in fermentation and growth experiments. The organism is a homolactic facultative bacterium requiring CO2 for growth. Anaerobically it fixes CO2 and formate, acetate, lactic, and succinic acids are the products of glucose fermentation, but when CO2 is limiting, the fermentation is essentially homolactic. In the presence of oxygen, glucose is oxidized to acetate and CO2, although CO2 and other unknown factors are still required to induce growth. Under aerobic conditions the maximum growth yields are obtained. Attempts to substitute the CO2 requirement with malate or fumaric acid were partially successful, supporting the conclusion that CO2 functioned in part as a hydrogen accepotor. But CO2 was still required to obtain the maximum growth, consequently CO2 functions as a growth requirement in a second unknown manner. Factors influencing the course of these fermentations are described.

NUTRITION AND GROWTH OF SEVERAL BLUE‐GREEN ALGAE

LITTLE ATTENTION has been given to the more general features of the physiology of the blue-green algae. Specific attention has been given to nitrogen fixation (e.g., Allison et al., 1937; Burris and Wilson, 1946; Fogg, 1947) and limited aspects of photosynthesis (e.g., Emerson and Lewis, 1942; Frenkel et al., 1950; Duysens, 1952; Brown and Webster, 1953). Nutritional requirements have been investigated, notably by Fogg (1949), Gerloff et al. (1950, 1952) and Allen (1952). However, no study has been carried to the point of developing a blue-green alga as a reliable tool organism for physiological studies. There have been two obstacles to such development. One may be attributed to the difficulties of isolation and the lack of species in pure culture which suspend readily and submit to simplicity of manipulation possible with green algae such as Chlorella and Scenedesmus. A second difficulty arises from inadequate provision of carbon dioxide inherent in most of the culture methods used. Nutritional requirements have been defined in terms of the maximum growth yield obtained in cultures in cotton-stoppered flasks. Methods have not been developed for routine study of growth rate, a characteristic far more useful and interpretable for physiological work. The' present paper presents a development of culture media and methods which has led to description of the salient growth characteristics of three blue-green algae: Anabaena variabilis, Anacystis nidulans, and Nostoc muscorum G. Fragmentary data on three other blue-green algae are included. MATERIALS AND METHODS.-Because of the uncertainties of taxonomy of the simpler algae the species used will be described in terms of their history. 1. Anabaena variabilis (Kiitzing). Filamentous, but filaments very short in turbulent culture; isolated by and obtained from R. C. Hecker as Cylindrospermum sp. (1950); revised identification by E. G. Pringsheim. 2. Anacystis nidulans. Twoto four-cell filaments, but unicellular in turbulent culture; established as a unicellular culture by one of us (WK) and purified by M. B. Allen, tentative identification by F. Drouet; original description not found. 3. Nostoc muscorum G (Kiitzing). Filamentous, but filaments short in turbulent culture; obtained from G. C. Gerloff. 4. Nostoc muscorum A (Kiitzing). Filamentous, forming clumps even in turbulent culture; isolated by and obtained from F. E. Allison. 5. Anabaena cylindrica (Lemmerman) . Fila-