Growth Of Candida Utilis Research Articles

Comparison of experimental methods for determination of the volumetric mass transfer coefficient in fermentation processes

Mass transfer in bioreactors has been examined. In the present work, dynamic methods are used for the determination of K L a values for water, model media and a fermentation broth (Candida utilis) in an airlift reactor. The conventional dynamic method is applied at the end of the microbial process in order to avoid an alteration in the metabolism of the microorganisms. New dynamic methods are used to determine K L a in an airlift reactor during the microbial growth of Candida utilis on glucose. One of the methods is based on the continuous measurement of carbon dioxide production while the other method is based on the relationship between the oxygen transfer and biomass growth rates. These methods of determining K L a does not interfere with the microorganisms action. A theoretical mass transfer model has been used for K L a estimation for the systems described above. Some differences between calculated and measured values are found for fermentation processes due to the model is developed for two-phase air-water systems. Nevertheless, the average deviation between the predicted values and those obtained from the relationship between oxygen transfer and biomass production rates are lower than 25% in any case.

Determination of biomass yield for growth of Candida utilis on glucose: Black box and metabolic descriptions

Similar to some complex chemical systems, many reactions are involved in a microbial process. One of the initial tasks for both systems consists of considering the stoichiometric relations among the different chemical reactants. In the present work, a methodology to establish the stoichiometric relations in microbial processes is shown. The yield of biomass from the C-source can be calculated from these relations by using two types of system descriptions found in the literature, the black box model and metabolic description. The former represents microbial growth by means of a chemical reaction which contains the accumulating compounds. The description is based on element, electric charge and Gibbs energy balances. The metabolic model also describes the intracellular biochemical reactions. The model is based on the specification of a set of reactions which contain all the accumulating and catalytic species. In the present work, the biomass yield is calculated for the Candida utilis–glucose system by using both models. Results are compared with the measured yield and the available data in the literature, showing a good agreement.

Continuous growth ofCandida 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. The cyclic regime was found to result in culture synchrony. Parameters obtained on the basis of cell counts displayed a high sensitivity to changes in limitation where as the remaining parameters were less sensible.

Studies on the growth of Candida utilis on d-galacturonic acid and the products of pectin hydrolysis

Candida utilis was found to utilize d-galacturonic acid for cell growth, the incubation conditions being similar to those reported for growth on other substrates. At concentrations of d-galacturonic acid below 3 g l −1 cell yields were similar to those obtained using glucose, although at higher concentrations cell yields were reduced. Small, regular increases in the concentration of d-galacturonic acid substantially increased cell yields under the incubation conditions employed. Poly- d-galacturonic acid, hydrolysed by a fungal polygalacturonase [poly(1,4-α- d-galacturonide) glycanohydrolase, EC 3.2.1.15] prior to cell growth, yielded 27 g C. utilis cells/100 g substrate. Acid-hydrolysed pectin yielded 23 g cells/100 g substrate but no cell growth was found using pectin which had been degraded by alkali. The possibility of using pectin materials for the production of singlecell protein in a modified Symba process is discussed.

SCP from pineapple (Ananas sativa Schutt)

Pineapple cannery effluents are available nearly round the year. The effluents are rich in microbially utilizable nutrients and when supplemented with ammonia support good growth of Candida utilis and Hansenula sydowiorum. The latter strain produces 45.0 g/l, 21.9 g/l, 1.5%, and 6.4% of cell biomass, protein, DNA, and RNA respectively in batch fermentations of such a medium. Amino acid profile, digestibility, NPU, and actual feed experiments confirm the applicability of the product. Concomitantly, a 90% reduction in BOD5 value of the effluent can be effected during this process which otherwise proves to be troublesome.

Russian Article pp. 255–266

AbstractThe growth of the yeast Candida utilis VKM‐Y‐2332 was investigated during the cultivation on a mineral medium with addition of ethanol in the regime of the chemostat and the pH‐auxostat. The composition of the macroelements of the biomass produced by Candida utilis VKM‐Y‐2332 was studied.Stoichiometric equations of the growth process of the examined yeast strain on ethanol were presented.The growth of Candida utilis on ethanol and glucose was also characterized by the way of comparision.

Production and consumption of NADPH and NADH during growth of Candida utilis on xylose

Production and consumption of NADPH and NADH during growth of Candida utilis on xylose

Treatment variables and amino acid profile of acid-treated straw

Treatment variables such as acid treatment, hydrolysis time, and liquid-to-solid ratio were analysed for straw treated for possible use as animal feed. The acids used were 0·26 n and 0·5 n HCl, 0·5 n H 3PO 4, 0·28 n and 0·5 n H 2SO 4 and a combination of 0·15 n H 3PO 4 and 0·23 n HCl. The fermentability of acid-treated straw measured by the growth of Candida utilis was highest when 0·23 n HCl plus 0·15 n H 3PO 4 were used to hydrolyse the straw. The lowest cell growth occurred with 0·5 n HCl, while the rest of the acid treatments resulted in non-significant differences. The time of hydrolysis (10 or 30 min) and the liquid-to-solid ratios (3/1 or 5/1) had no significant effect on microbial growth. Different acids released different amounts of sugar during hydrolysis. In general, the higher the acidity the higher the sugar yield. There was an interaction between the acid treatment and the liquid-to-solid ratio. Overall, 30 min hydrolysis released more sugar than did hydrolysis for 10 min. In the HCl/H 3PO 4-treated straw the protein was increased two-fold after fermentation. The amino acid profile of the straw fermented with Aureobasidium pullulans was similar to that of alfalfa.

Resistance to Fluorouracil in Candida utilis: Effects on the Uptake of Pyrimidines and Amino Acids

5-Fluorouracil powerfully inhibits growth of Candida utilis. Isolates that are resistant to fluorouracil all have a reduced ability to transport uracil but most also have other defects. Their capacity to take up a wide range of amino acids is greatly reduced, as is their ability to alter rates of amino acid transport during nitrogen starvation. These isolates may be defective in the coupling of energy generation to transport systems.

Growth of Candida utilis on enzymatically hydrolysed cassava

Enzymatically hydrolysed cassava starch was used for C. utilis cultivation. Highly efficient starch hydrolysis was achieved with a 92% DE syrup obtained after 15–20h. Cyanide content fell during cassava processing to very low levels in the hydrolysate. Comparison of biomass yields and protein of C. utilis using molasses and cassava hydrolysate as substrates demonstrates the potential of the latter for yeast production.

Growth of Candida utilis on a mixture of monosaccharides, acetic acid and ethanol as a model of waste sulphite liquor.

Candida utilis cultivated under batch conditions in a synthetic medium with a mixture of different carbon sources utilized first D-glucose and then D-galactose, D-mannose, D-xylose, L-arabinose, ethanol and acetic acid. The effect of acetic acid was primarily a function of pH and the physiological state of the inoculum. At pH 4.5, acetic acid at a concentration of 1 g/l increased the specific growth rate, reduced time of cultivation and increased yield of the yeast dry weight. The yield from acetic acid was 61%. In the presence of a higher content of acetic acid (3--6 g/l) the yield was only 18--26%. The yield calculated only from monosaccharides increased but the yield with respect to total carbon sources was lower. The specific growth rate decreased as well. The addition of ethanol also resulted in an increase of the production and yield of the yeast dry weight but the cultivation time was prolonged. The simultaneous utilization of carbon sources of the studied mixture modelling a sulphite fermentation medium with ethanol is advantageous. However, due to physiology of the yeast, it is most suitable to cultivate a strain adapted to utilizable carbon sources in a continuous way, in the presence of their limiting concentrations in the cultivation medium.

Influence of acetate on the growth of Candida utilis in continuous culture.

Candida utilis was grown on acetate in chemostat cultures that were, successively, carbon and ammonia-limited (30° C; pH 5.5). With carbon(acetate)-limited cultures, the specific rate of oxygen consumption (qO2) was not a linear function of the growth rate but was markedly stimulated at the higher dilution rates, thus effecting a marked decrease in the YO value. This increased respiration rate, and decreased yield value, correlated closely with a marked increase in the extracellular acetate concentration. Under ammonia-limiting conditions, very low YO values were found, generally comparable with those found with carbon-limited cultures growing at the higher dilution rates, but these varied markedly with the extracellular acetate concentration. Thus, when the unused acetate concentration was raised progressively from about 5 g/l to about 21 g/l, the YO value decreased non-linearly from 11.4 to 5.8. When the extracellular acetate concentration was further increased to 25 g/l, growth was inhibited and the culture washed out. This relationship between respiration rate and the extracellular concentration of unused acetate was also markedly influenced by the culture pH value. Thus, with a fixed extracellular acetate concentration (16±2g/l) and dilution rate (0.14 h−1), lowering the culture pH value progressively from 6.9 to 5.1 effected a marked and progressive increase in the respiration rate. Further lowering of the culture pH to 4.8, however, caused a complete collapse of respiration. In contrast to this situation, progressively lowering the pH value of an acetatelimited culture from 6.9 to 4.5 affected only slightly the culture respiration rate, and growth was possible even at a pH value of 2.5. These results are discussed in the context of the possible mechanisms whereby acetate exerts its toxic effect on the growth of C. utilis.

Assay and regulation of S-adenosylmethionine synthetase in Saccharomyces cerevisiae and Candida utilis.

A simple and sensitive assay for S-adenosylmethionine (SAM) synthetase is described which depends on the quantitative separation of the product, [14CH3]S-adenosylmethionine, from the substrate, L-[14CH3]methionine, on a Bio-Rex 70 column. L-Methionine protects the enzyme during preparation of cell extracts by sonic treatment but causes repression of enzyme activity during growth of Candida utilis. The presence of 5 mM methionine in the growth medium repressed SAM synthetase specific activity threefold compared to the specific acitivity of the enzyme isolated from cells grown in unsupplemented medium. Conversely, the presence of methionine in the growth medium resulted in an 80-fold increase in the intracellular concentration of SAM as compared to the Sam accumulated intracellularly in unsupplemented cultures.

Piericiden A sensitivity, site 1 phosphorylation, and reduced nicotinamide adenine dinucleotide dehydrogenase during iron-limited growth of Candida utilis.

It has been reported that cells of Candida utilis, grown in continuous culture under iron-limited conditions, develop site 1 phosphorylation, without the appearance of piericidin sensitivity and without changes in the iron-sulfur centers of NADH dehydrogenase, on aeration in the presence of cycloheximide, as well as on increasing the supply of iron during growth. These findings were reinvestigated in the present study. The parameters and properties followed during these transitions were sensitivity of NADH oxidation to piericidin, presence or absence of coupling site 1, EPR signals appearing on reduction with NADH or dithionite, the specific activities of NADH oxidase, NADH-ferricyanide reductase, and NADH-5-hydroxy-1,4-naphthoquinone (juglone) reductase, and the kinetic behavior of NADH dehydrogenase in the ferricyanide assay. Monitoring the rates of oxidation of NADH in submitochondrial particles with artificial oxidants, observing the kinetics of the ferricyanide assay, and measuring the concentration of iron-sulfur centers elicited by EPR permitted ascertaining the type of NADH dehydrogenase present and its relative concentration in different experimental situations. It was found that on gradually increasing the concentration of iron during continuous culture (transition from ironlimited to iron- and substrate-limited growth), as well as on aeration of iron-limited cells, coupling site 1, piericidin sensitivity, NADH-ferricyanide activity, and iron-sulfur centers 1 and 2 increased concurrently, with concomitant decline of NADH-juglone reductase activity. Cycloheximide prevented all these changes. Iron-sulfur centers 3 plus 4 underwent relatively little increase during these transitions. It is concluded that in both of these experimental conditions a replacement of the type of NADH dehydrogenase present in exponential phase cells by that characteristic of stationary phase cells occurs and that the appearance of site 1 phosphorylation, piercidin sensitivity, and iron-sulfur centers 1 plus 2, all associated with the latter enzyme, is a consequence of this replacement. No evidence was found for the development of coupling site 1 without the appearance of piericidin sensir th

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 response by microorganisms to steady state growth in controlled concentrations of oxygen and glucose. I. Candida utilis

AbstractDissolved oxygen and glucose concentrations have been independently maintained at various concentrations for extended periods during growth of Candida utilis in continuous culture. Simultaneous observations of cytochrome concentration, growth rate, rates of uptake of oxygen and glucose and rates of production of CO2, ethanol and acid have been made during steady states at various levels of oxygen and glucose. There is an inverse relationship between dissolved oxygen and cytochrome and between glucose cocentration and cytochrome.Studies of the transient state following a step change from high to low dissolved oxygen show that there is a lag of about 10 hr during which there is no change in the above parameters. This is followed by rapid oscillatory changes in cytochrome content and a change to a more fermentative metabolism.

Utilization of Rice Husk

or sulfuric acid, pulverization of rice husk became easy and its volume became one-fourth of the original. Xylose was obtained as crystal at the level of 4% yield from the extract of rice husk prepared through acid treatment after boilng in alkaline solution. The growth of Candida utilis in the extract of rice husk containing urea as a nitrogen source was slow and the ratio of sugar uptake was only 20%. By the addition of sweet potato juice and the culture of the yeast adapted previously to the medium, the ratios of sugar uptake and the yeast cells to the consumed sugar were elevated to the level of 90% and 140% respectively.

The operational flexibility of the phased culture technique, as observed by changes in the cell cycle of Candida utilis.

The operation of a continuous phasing technique was examined with regard to synchrony and growth of Candida utilis at different doubling times. A nitrogen-limited medium and an energy-limited medium were compared. Numbers of viable cells, dry mass, ribonucleic acid (RNA), deoxyribonucleic acid (DNA), various phosphorus-fractions, and protein were measured.In a nitrogen-limited medium the continuous phasing technique provided good synchrony (65%–80%), and permitted control and variation of the doubling time up to 9 h. Dry mass, various P-fractions, and DNA increased linearly during all cycle times. The cell doubling time was adjustable to the cycle time imposed by the technique. The nitrogen source was always assimilated within 4 h, whatever the length of the cycle employed. The associated pattern of changes in the amino acid pool, protein, and RNA contents of the cells, though characteristic, underwent some modifications with change in doubling time.An inverse relationship between the amount of nitrogen available to the cells for their reproduction and the corresponding doubling time was found.In an energy (glucose)-limited medium the technique appeared to be restricted to a doubling time where the energy source in the medium lasted until the end of the cell's life cycle. The degree of synchrony was 70–75%. A variation of the doubling time by the technique did not seem possible in glucose-limited medium since no adjustment of the growth rate to the imposed cycle time could be observed.