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1

Minimization of the relative error and variability coefficient at certain procedure for determination of the microorganisms' growth model parameters

100%
Cibis E.
Polish Journal of Food and Nutrition Sciences
|
2002
|
tom 11/52
|
nr 4
The aim of the present paper was to analyse relative errors and variability coefficients for estimated values of maximum specific growth rate (µmax) and saturation constant (Ks) in the Monod's growth model in the case when these values are determined on the basis of data from steady states of two chemostatic continuous cultures, and also on the basis of the above to propose the procedure for the dilution rate selection so that the analysed quantities attained minimum values. The above-mentioned relative errors and variability coefficients were analysed at assumption that the relative errors of determined values used for estimation, i.e. the dilution rate and substrate concentration in fermenter, are constant. It was found that in the analysed estimation method both relative error so as variability coefficient for saturation constant are higher than for maximum specific growth rate and that the relative errors and variability coefficients values for both estimated parameters are then minimum when one culture is carried on at possible low dilution rate and the second at the dilution rate close to the washout rate. It was also established that carrying on one continuous culture at the fixed in advance dilution rate it cannot be possible to always select the dilution rate of the second culture, so that the simultaneous minimization of relative error for µmax and Ks was possible. It also relates to the minimization of variability coefficient.
2

Próby określania zawartości cukrów na podstawie zmian wartości pH podczas hodowli ciągłej drożdży paszowych Candida utilis

63%
Zmaczynski K., Cibis E.
Przemysł Fermentacyjny i Owocowo-Warzywny
|
1990
|
tom 34
|
nr 08-09
3

Skład wywaru melasowego i wykorzystanie jego składników pokarmowych przez drożdże paszowe

63%
Cibis E., Zmaczynski K.
Przemysł Fermentacyjny i Owocowo-Warzywny
|
1990
|
tom 34
|
nr 03
4

Parametry technologiczne i stabilnośc procesu w dwunaczyniowej, pH-statowej hodowli drożdży Candida utilis przy różnych wariantach dozowania brzeczki wywarowo-melasowej

63%
Zmaczynski K., Cibis E.
Przemysł Fermentacyjny i Owocowo-Warzywny
|
1991
|
tom 35
|
nr 08
5

Optimization of citric acid production from glucose syrup by Yarrowia lipolytica using response surface methodology

63%
Rymowicz W., Cibis E.
Electronic Journal of Polish Agricultural Universities. Series: Biotechnology
|
2006
|
tom 09
|
nr 1
A new criterion was proposed to evaluate the process of citric acid biosynthesis by the acetate negative mutant strain Yarrowia lipolytica AWG-7 cultivated on glucose syrup by the repeated-batch method. This criterion imparts the same weight to the overall amount of the citric acid production and to the trend in citric acid concentration. To determine the optimum levels of bacto-peptone, ammonium chloride and potassium dihydrogen phosphate which maximize the proposed objective function, a central composite design was developed using 50 ml repeated-batch fermentation. The design involved 20 processes conducted with various combinations of the five values of these three parameters. The experiments produced empirical values of the proposed criterion which were then approximated with the fourth-order polynomial. It was found that the optimal concentrations of bacto-peptone, ammonium chloride, and potassium dihydrogen phosphate equaled 8.5; 159.8 and 65 mgl-1, respectively.
6

Aerobic biodegradation of vinasse by a mixed culture of bacteria of the genus Bacillus: optimization of temperature, pH and oxygenation state

51%
Ryznar-Luty A., Krzywonos M., Cibis E., Miskiewicz T.
Polish Journal of Environmental Studies
|
2008
|
tom 17
|
nr 1
101-112
The aim of the study was to optimize the temperature, pH and oxygenation state for the aerobic biodegradation of vinasse using a mixed culture of thermo- and mesophilic bacteria of the genus Bacillus. At the initial stage of the study a series of experiments was performed in shake flasks over the temperature range of 30 to 65°C and an initial pH of the medium ranging between 5.40 (the pH of vinasse) and 9.5 in order to determine the optimal values of the two parameters (T = 58°C, pH = 8.35) and thus maximize the extent of COD reduction (60.88%). At the subsequent stage, with the optimal values of temperature and initial pH, batch biodegradation processes were conducted in an STR with aeration at 1.0 vvm and two stirrer speeds, 550 rpm and 900 rpm, which provided a reduction in COD of 77.56% and 76.48%, respectively. With 900 rpm, a concomitant rise in the biodegradation rate was observed. The extent of COD reduction increased to 85.37% when biodegradation was conducted at 58o C (optimal temperature) and a stirrer speed of 900 rpm, the pH being maintained at 8.35 throughout the process.
7

Optimization of single-cell-biomass production by Yarrowia lipolytica using response surface methodology and pulse method

51%
Musial I., Rymowicz W., Cibis E.
Electronic Journal of Polish Agricultural Universities. Series: Biotechnology
|
2004
|
tom 07
|
nr 1
8

Continuous biodegradation of sugar beet distillery stillage in an aerobic stirred-tank reactor: the effect of hydraulic Retention Time

51%
Lutoslawski K., Cibis E., Krzywonos M., Ryznar-Luty A.
Polish Journal of Environmental Studies
|
2020
|
tom 29
|
nr 4
9

Biodegradation of the potato slops with a mixed population of aerobic bacteria - optimisation of temperature and pH

51%
Krzywonos M., Cibis E., Miskiewicz T.
Polish Journal of Food and Nutrition Sciences
|
2002
|
tom 11/52
|
nr 4
The aim of the study was to optimise the parameters (temperature and pH) of potato slops biodegradation with a mixed population of thermophilic and mesophilic aerobic bacteria of the genus Bacillus. Temperature and pH were optimised during 93-hour growth in the shake-flasks at 30 to 60°C and pH 3.88 to 9.0. The course of the biodégradation process at optimal temperature and pH, and with increased oxygen supply, was investigated in an aerated stirred-tank bioreactor. During cultivation in shake-flasks, the following phenomenon was observed: the higher was the process temperature, the sooner the maximal number of cells was achieved. Taking into account the need of maximising the extent of the COD reduction, the optimal temperature and pH values (calculated on the basis of experimental data) were 44.6°C and 7.40. With such parameters, a 22.5% reduction in COD was obtained. The highest number of cells (2.3x109/mL) was achieved at 30°C and pH 5.96. The biodégradation of potato slops in the stirred-tank bioreactor yielded an 86.5% reduction in COD. The process was carried out for 53 hours but most of the pollutants were degraded at the initial stage (21 h). Of the compounds which were utilised as carbon sources and occurred in the highest amounts, lactic, propionic and acetic acids were removed completely (100%), while the removal of reducing substances and glycerol exceeded 90%.
10

Kinetic analysis of Saccharomyces cerevisiae cell immobilization onto ceramic supports

45%
Cibis E., Zboromirska-Wnukiewicz B., Garncarek Z., Gasperowicz A., Krzywonos M.
Polish Journal of Food and Nutrition Sciences
|
2002
|
tom 11/52
|
nr 3
Saccharomyces cerevisiae yeast was immobilized on Al-70 ceramic supports with and without changing their surface zeta-potentials via silyla- tion. Preliminary ethanol fermentation was carried out with yeast cells immobilized on a silylated support. The immobilization technique involved recirculation of the yeast suspension through a column packed with ceramic support material. With a low (under 1.7 g/L) initial biomass concentration in the suspension, cell immobilization was a single-stage process where the amount of yeast cells fixed on the ceramic bed can be expressed as an exponential time function. With high (greater than 3.1 g/L) initial biomass content in the suspension, immobilization was a two-stage process. In each stage, the quantity of the yeast fixed on the carrier can also be regarded as an exponential time function. Specific immobilization rate was proposed as a main criterion for assessing the course of the cell immobilization process. The increase of the initial yeast concentration in the suspension brought about a decrease of the specific immobilization rate in the single-stage process and in the first phase of the two-stage process. Silylation (in order to achieve opposite zeta-potential for the support and the yeast cells) accounted for a noticeable increase of specific immobilization rate both in the single-stage process (by 144%) and in the first phase of the two-stage process (by 61%). Ethanol fermentation involving yeast cells immobilized on a silylated ceramic carrier had an efficiency which accounted for 83.5% of the theoretical efficiency.
11

Optimization of ergosterol biosynthesis by Saccharomyces cerevisiae - choice of objective function

45%
Cibis E., Garncarek Z., Miskiewicz T., Rychtera M., Borowiak D.
Polish Journal of Food and Nutrition Sciences
|
2001
|
tom 10
|
nr 3
The objective of the study was to optimize ergosterol production by Saccharomyces cerevisiae in continuous and fed-batch cultures. Use was made of three optimization criteria: ergosterol yield related to the mass unit of the substrate supplied to the fermenter, and two criteria proposed for the purpose of the study, both incorporating (in addition to ergosterol yield) ergosterol content in yeast cells and proportion of ergosterol in the total ∆ 5,7-sterols content. In both culture types, specific growth rate was found to affect the content of ∆5,7-sterols in the yeast cells. In continuous culture, three of them (ergosterol, dehydroergosterol, and unidentified sterol) reached their maximum at the dilution rate of 0.74, 0.102 and 0.131 h-1, respectively. For ergosterol and for the unidentified sterol, these were the dilution rates at which ethanol content in the culture medium began to increase. Dihydroergosterol content was an increasing function of dilution rate. In the fed-batch culture with purely oxidative assimilation of glucose, ∆5,7- sterols content in yeast cells (except that of dehydroergosterol) increased with increasing specific growth rate. Optimization carried out with the three objective functions mentioned above showed that they reached their maxima at essentially the same argument values - both in continuous and fed-batch cultures. This indicates that the ergosterol yield criterion can be substituted for the two, more sophisticated, optimization criteria. The optimum dilution rate for continuous culture was 0.13 h-1, and the optimum time of fed-batch culture ranged between 6 and 8 h.
12

Biodegradation of potato slops with a mixed population of bacteria of the genus Bacillus - determination of the process conditions

45%
Cibis E., Krzywonos M., Trojanowska K., Miskiewicz T., Ryznar A.
Electronic Journal of Polish Agricultural Universities. Series Food Science and Technology
|
2004
|
tom 07
|
nr 2
The study has been carried out in order to optimise the conditions for the biodegradation of potato slops with a mixed population of thermophilic and mesophilic bacteria.
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