Yeast Candida Utilis Research Articles

In vivo 31P NMR studies on the role of the vacuole in phosphate metabolism in yeasts.

31P NMR was used to study the dynamics of phosphate pools during substrate utilization by aerobic and anaerobic suspensions of the yeast Candida utilis and by aerobic suspensions of the yeast Brettanomyces intermedius. In both yeast, the cytoplasmic pH was monitored; in C. utilis also the vacuolar pH could be measured. When glucose was used as a substrate for C. utilis, the vacuolar store of inorganic phosphorus (both orthophosphate and polyphosphate) was mobilized to replenish cytoplasmic phosphate which had become very low due to the build-up of high sugar phosphate levels. The hydrolysis of polyphosphate was glucose-dependent; it did not occur with ethanol as the substrate. After glucose depletion resynthesis of polyphosphate occurred only under aerobic conditions; anaerobic C. utilis cells continued to hydrolyze vacuolar polyphosphate. This difference between the aerobic and anaerobic suspension could be related to differences in cellular ATP levels. When ethanol was employed as a substrate, both Candida utilis and Brettanomyces intermedius exhibited a substantial increase in polyphosphate levels. These observations suggested a dual role for polyphosphate in yeasts both as a phosphate and an energy store. The cytoplasmic pH in C. utilis displayed characteristic responses to metabolic changes during glucose degradation. B. intermedius experienced a strong cytoplasmic acidification upon ethanol utilization due to acetic acid formation. The mechanism of transport of Pi across the vacuolar membrane in C. utilis appeared to be different from that reported for the plasma membrane.

“Petite-like” mutants of the petite-negative yeastCandida utilis after treatment with ethidium bromide

“Petite-like” colonies of the petite-negative yeastCandida utilis were obtained after the cells were treated with the mutagenic agent ethidium bromide (Eth-Br) (25 μg/ml). The lack of ability to grow on nonfermentable substrates like glycerol, lactate, and ethanol and the tetrazolium assay revealed the respiratory deficiency of two isolated colonies. The mutation frequency was 30 times higher than spontaneous mutation (3×10−5). Doubling time (td) and specific growth rate (μ) of “petite-like” respiration-deficient mutants were studied in complete medium. A td increase of 1.8 times over that of respiration-sufficient parental cells was attributable to the slower division rate of the “petite-like” cells. Assimilation and fermentation properties showed the absence of respiratory capacity. “Petite-like” colonies did not grow on nonfermentable carbon sources that parentalC. utilis readily utilize for growing.

Production of biomass from sulphite liquors in tower fermentor with forced circulation

Cultivation of the yeast Candida utilis on sulphite liquors was studied in a tower fermentor with ejector-type gas distributor and additional bubble bed showering. The aim of the work was to test the fermentor applicability for the cultivation process studied and to obtain data characterizing the fermentation in the tested unit. The effect of medium composition and dilution rate on selected cultivation parameters was determined in the fermentor with active volume 0.1 m3 and the hydrodynamic and energy characteristics of the apparatus were evaluated. The experimental results proved the fermentor to be suitable for the cultivation process studied. Favourable effect of the optimized fermentation medium was observed both on the values of characteristic cultivation parameters and on the efficiency of the utilization of energy supplied to the system.

"Critical size" in the yeast Candida utilis as influenced by physico-chemical parameters of cultivation.

The “critical size” of cells of budding yeasts was demonstrated to be influenced by physicochemical parameters of cultivation (temperature, aeration), type of substrate under conditions of nonlimited growth, “history” of the inoculum and its genealogical age, in addition to medium composition.

Comparison of ethanol feed-type on yeast growth at various po2 levels

The growth characteristics of the yeastCandida utilis in the individual stages of a multistage tower fermentor obtained with single- and multistream ethanol feeding were compared. In addition, various types of pure oxygen supply were tested for each type of ethanol feed. The results, obtained from steady-state continuous cultures, provided evidence that the two types of ethanol and oxygen supply significantly affect the cell growth rate, ethanol dissimilation rate, acetate excretion in the medium, biomass yield and productivity.

RNA removal from Candida utilis by chemical and thermal treatments

AbstractThe removal of the content of nucleic acids of fodder yeast (Candida utilis) by treatment with HCl or heat shock was investigatedAcid concentrations between 5 and 15% (on dried matter basis) were used. A maximal removal of the content of nucleic acids of 88% was realized wheńn was worked with 15% HCl, 90 °C during 30 minutes. But under this conditions were observed high demanges of protein and also of some essential amino acidsGood results for diminishing the content of nucleic acids were reached with the highest concentration of acid and a treatment during 20 minutesThe experiments with heat shock were carried out at 68 °C, different times for heating and different contents of yeastIn this way better results than for treatment with acid according to diminishing the content of nucleic acids and yield of protein and essential amino acids were reachedA removal of over 80% of the content of nucleic acids was achieved in all cases.

Stimulation by pH of cell cycle initiation in the yeast Candida utilis

The effect of shifting pH of the growth medium on cell cycle initiation by the yeast Candida utilis was studied. The yeast was grown by the phased method of cultivation with nitrogen source (ammonium) in growth limiting concentrations and with a phasing period (imposed doubling time) of 6 h. The pH of the culture during the phased growth was maintained between 2.0 and 2.1. The rate of cell cycle initiation as determined by the rate of bud emergence was 24% per hour. If the pH of the culture was shifted to 6.0 at the beginning of the phasing period and maintained at that level for the rest of the phasing period the rate of bud emergence increased to 50% per hour. The increased rate of bud emergence was accompanied by a fast uptake of oxygen and the growth-limiting nutrient and by a reduction in the respiratory quotient. The results suggest that the pH shift accelerated cellular processes necessary for cell cycle initiation.

The effect of inorganic phosphate on the stability of some enzymes.

In the presence of 5nM-P1, 6-phosphogluconate dehydrogenase from the yeast Candida utilis is more resistant to proteolysis and to the inactivating action of some chemical and physical agents. P1 also protects other enzymes against proteolysis. A hypothesis for the mechanism of the stabilizing action of P1 is advanced.

Single‐cell protein production from spent sulfite liquor utilizing cell‐recycle and computer monitoring

AbstractSpent sulfite liquor (SSL), a waste product of the paper pulping industry, is produced at a rate of 1 ton (dry basis) per ton of pulp. The sugar content of SSL is about 30 g/L. To reduce the biological oxygen demand (BOD) of SSL before disposal, torula yeast (Candida utilis) is produced by a continuous culture process, the productivity of which is limited by sugar concentration and cell growth rate. To increase productivity, a recycle system has been designed and tested. Cells were sedimented continuously with a flocculating agent (bentonite) before being recycled to the fermentor. A bentonite concentration of 0.02 g/g cell was required. A computer monitoring system based on material balancing techniques was developed to monitor and control the recycle system. With this computer system, productivity was raised to 6.1 g/L h, with cell concentration up to 65 g/L in the recycle stream and 24 g/L in the fermentor. This represents a productivity increase of 150% over continuous culture with no recycle.

Growth of yeast Candida utilis in crotonaldehyde containing media

The inhibitory influence of the higher concentration of 20butenal, crotonaldehyde was followed during the batch and long-term continuous fermentation of Candida utilis growing on synthetic ethanol. Most crotonaldehyde is removed from the medium by biotransformation. Crotonaldehyde inhibits the growth, lengthens the lag phase and decreases the biomass yield and the content of crude proteins in the biomass. The yeast C. utilis is capable of growing on media containing very high concentrations of inhibitor in the in-flow during continuous cultivation. Uncharacteristic transport oscillations of the content of crotonaldehyde were observed for which acidic groups on the cell membrane are probably responsible. A sensitive method which is suitable for measuring very low concentration of crotonaldehyde in aqueous solutions is described. Crotonaldehyde acts as an uncompetitive inhibitor with slight mixed type of inhibition. An equation describing the kinetics of inhibition was derived.

Effect of multistream ethanol feeding on growth and physiological characteristics of Candida utilis in a multistage tower fermenter

The effect of using a multistream feed for carbon and energy supply on the growth and physiological activity of the yeast Candida utilis in a multistage tower fermenter has been studied. Measurements were made at steady states of continuous culture for single values of dilution rate, temperature and pH in all stages of the fermenter and with the same total ethanol supplied. A comparison of the results obtained with multistream and single-stream ethanol feeds revealed that the type of ethanol feed influences the cell growth rate, rate of ethanol dissimilation, biomass yield, productivity and the cell physiology in the individual stages of the fermenter. Multistream ethanol feeding eliminates the growth inhibition due to insufficient energy production from ethanol oxidation at higher partial pressure of oxygen in the aeration gas. Using the optimal type of ethanol feed, better process parameters for SCP production are achieved.

The role of glutathione in amino-acid absorption. Lack of correlation between glutathione turnover and amino-acid absorption by the yeast Candida utilis.

The rate of degradation of glutathione has been determined in the yeast Candida utilis by using a method that minimizes the effect of amino-acid recycling. When yeast are grown in amino-acid-free medium, the half-life of glutathione was found to be 230 min. C. utilis was also found to absorb various L-amino acids rapidly without producing any significant decrease in the half-life of glutathione. While the gamma-glutamyl cycle is thus operating in C. utilis, the rate of degradation of glutathione is found to be 100 times too slow for the cycle to be mediating the transport of these amino acids.

Nutritive value for growing pigs of pekilo protein and torula yeast grown in spent sulphite liquour

The digestibility and nutritive value of pekilo protein (Paecilomyces varioti), and torula yeast (Candida utilis) were determined for four pigs weighing 35—50kg. The proportion of pekilo or torula was 30% of the barley-based diet. The crude fat was determined by the standard ether extraction method and by the HCl-ether method. The first method indicated a low fat content and a highly negative digestibility of fat, but the second showed that the pig is able to digest and absorb a large part of the ether-insoluble fat. The energy value thereby increased 14 % for pekilo and 12 % for torula over those obtained by the conventional ether method. The same energy value was obtained for barley by both methods. The energy values (HCI-ether method) obtained for pekilo and torula were 0.96 and 0.95 F.U./kg DM(F. U. = 0.7 kg starch), or 13.41 and 12.98 MJ ME/kg DM, respectively. The protein values, corrected for nucleic acid nitrogen, were 434 and 358g DCP/kg DM. The only significant difference between pekilo and torula was the DCP value (P< 0.001). The nitrogen balances in the pekilo and torula trials were very high and identical (24.4 and 24.0 g N/d), confirming the value of these feeds as protein supplements to cereal feeds for pigs.

Quaternary pyridinium compounds formed by reaction of primary amines with alkanals and their antimicrobial activities.

Seventeen alkyl-substituted quaternary pyridinium compounds were synthesized by the condensation reaction of amino acids and primary amines with alkanals. The growth-inhibitory capabilities of these pyridiniums were investigated against gram-negative and gram-positive bacteria (Escherichia coli and Streptococcus thermophilus), as well as against a mold (Neurospora crassa) and yeast (Candida utilis). Most of the pyridiniums appreciably inhibited the growth of the microorganisms tested. l-Carboxymethyl-2-hexyl-3, 5-dipentylpyridinium betaine and l-(2hydroxyethyl)-2-hexyl-3, 5-dipentylpyridiriium chloride showed the greatest inhibitory activity. Least growth inhibition by pyridinium ions was observed for E. coli.

Rearing of sharptooth catfish larvae ( Clarias gariepnus Burchell, 1822: Clariidae) under controlled conditions

Clarias gariepinus larvae were fed on different diets: trout starter, soya bean flour, Torula yeast, Vital yeast, Tetramin, hard boiled egg yolk and plankton. The aim was to determine the suitability of dry feed as a first nutrient of catfish larvae. For the first 10 days larvae fed on Torula yeast ( Candida utilis) grew significantly faster (8.69 ± 1.76%) than the larvae fed on other foods, whereafter those larvae fed on plankton exceeded the yeast fed larvae in growth. Mortalities of larvae fed on yeast and plankton were negligible. Larval behaviour during feeding and digestion rates of the various feeds are discussed.

Application of tower bioreactors with forced circulation in biomass production

Characteristic hydrodynamic parameters of three selected types of bubble-type column reactors with forced liquid circulation were studied experimentally. Application of these units for the fermentation process - production of fodder protein by continuous cultivation of Candida utilis yeast on the synthetic ethanol was tested. Two modifications of the column reactor with the ejector gas distributor and the bubble type tower reactor with the central tube and forced internal circulation of the gas-liquid dispersion were selected. Diameter of all three reactors used was 0.3 m. The volumetric mass transfer coefficient (kLa) and gas holdup (εG) were determined both for the standard water-air system and under actual fermentation process conditions. The effect of the inlet ethanol concentration and of the dilution rate on the cultivation characteristics was determined during the cultivation experiments. The obtained results have proved that the studied reactor types are suitable for fermentation. Equipment with the ejector gas distributor can be recommended even for processes with high requirements on the oxygen consumption, while by the proposed construction arrangement the undesired foam formation in the system was successfully eliminated.

Effect of pH on the rate of Candida utilis cell cycle initiation.

The rate of cell cycle initiation (as determined by the rate of bud emergence) in yeast Candida utilis under ammonium-limited phased cultivation was dependent on the pH at which the yeast was grown.

Observations on the mitochondrial reticulum in the yeast Candida utilis as revealed by freeze-fracture electron microscopy.

Freeze-fracture of Candida utilis yeast cells grown to early logarithmic phase (5 h) and stationary phase (24 h) revealed a branched mitochondrial reticulum both in longitudinal and transverse cross-fracture studies. In contrast, the longitudinal and transverse sections of permanganate-fixed cells showed that the small ovoid or spherical mitochondria were located at the periphery of the cell, without formation of a reticulum. Data indicate that the separate mitochondrial profiles seen in thin sections of permanganate-fixed yeast cells are not separate round or ovoid mitochondria, but rather are cross-sections of the mitochondrial reticulum.

Development of amine oxidase-containing peroxisomes in yeasts during growth on glucose in the presence of methylamine as the sole source of nitrogen.

The metabolism of methylamine as the nitrogen source for growth of the non-methylotrophic yeast Candida utilis and the methylotrophic yeast Hansenula polymorpha was investigated. Growth of both organisms in media with glucose and methylamine was associated with the presence of an amine oxidase in these cells. The enzyme catalyses the oxidation of methylamine by molecular oxygen into ammonia, formaldehyde and hydrogen peroxide and it is considered to be the key enzyme in methylamine metabolism in the organisms studied. In addition to synthesis of amine oxidase, derepression of catalase, formaldehyde and formate dehydrogenase was also observed upon transfer of cells of the two organisms from media containing ammonium ions into media containing methylamine as the nitrogen source. The synthesis of enzymes was paralleled by the development of a number of large microbodies in the cells. Cytochemical staining experiments indicated that the amine oxidase activity was located in the microbodies in both organisms. Catalase-activity was also demonstrated in these organelles, which can therefore be considered as peroxisomes. The present contribution is the first description of a peroxisomal amine oxidase.

Symbiotic growth of a yeast and a bacteria in batch fermentors

Single cell protein was produced from cassava starch by symbiotic growth of the α-amylase producing bacteria Bacillus subtilis and the yeast Candida utilis, which is accepted as fodder. By batch fermentations it was shown, that the pH fluctuation during the fermentation and the inoculum were extremely important parameters.