Determination of the kinetic parameters in continuous cultivation byDebaryomyces hansenii grown on D-xylose

Duarte, Luís C.; Nobre, Alexandra; Gı́rio, Francisco M.; Amaral-Collaço, M. T.

doi:10.1007/bf02447728

Cited by 11 publications

(9 citation statements)

References 9 publications

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“…The air £ow rate was 2 l min 3I and the pH was automatically controlled at 5.5 by the addition of 4 M NaOH. Under either D-xylose or oxygen limitation a chemically de¢ned medium was used [10] except that citric acid and KI were replaced by EDTA and NaI, respectively. For ammonium-limited continuous cultures, the above medium was changed accordingly to (l 3I ): (NH R ) P SO R 0.754 g instead of 9.438 g. For phosphate-limited continuous cultivation, KH P PO R 0.055 g and K P SO R 1.566 g were used.…”

Section: Microorganism and Growth Conditionsmentioning

confidence: 99%

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Phosphate limitation stress induces xylitol overproduction by Debaryomyces hansenii

Tavares

1999

FEMS Microbiology Letters

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The physiological responses of xylose-grown Debaryomyces hansenii were studied under different nutritive stress conditions using continuous cultivation at a constant dilution rate of 0.055 h 3I . Metabolic steady-state data were obtained for xylose, ammonium, potassium, phosphate and oxygen limitation. For xylose and potassium limitation, fully oxidative metabolism occurred leading to the production of biomass and CO P as the only metabolic products. However, potassium-limiting cultivation was the most severe nutritional stress of all tested, exhibiting the highest xylose and O P specific consumption rates along with the lowest biomass yield, 0.22 g g 3I xylose. It is suggested that carbon was mainly channelled to meet the cellular energy requirements for potassium uptake. For the other limiting nutritional conditions increasing amounts of extracellular xylitol were found for ammonium, phosphate and oxygen limitation. Although xylitol excretion is not significant for ammonium limitation, the same is not true for phosphate limitation where the xylitol productivity reached 0.10 g l 3I h 3I , about half of that found under oxygen-limiting conditions, 0.21 g l 3I h 3I . This work is the first evidence that xylitol production by D. hansenii might not only be a consequence of a redox imbalance usually attained under semi-aerobic conditions, but additional physiological mechanisms must be involved, especially under phosphate limitation. Cell yields changed drastically as a function of the limiting nutrient, being 0.22, 0.29, and 0.39 g g 3I xylose for potassium, oxygen and phosphate limitation, respectively, and are a good indicator of the severity of nutritive stress. z

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Section: Microorganism and Growth Conditionsmentioning

confidence: 99%

“…In addition, dry weight measurements were carried out using 0.45-Wm cellulose acetate membranes (Gelman Sciences, Ann Arbor, MI, USA) [10].…”

Section: Determination Of Biomass Concentrationmentioning

confidence: 99%

Phosphate limitation stress induces xylitol overproduction by Debaryomyces hansenii

Tavares

1999

FEMS Microbiology Letters

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“…This is due to several factors, including the low resistance to ethanol stress of the yeasts (25). Optimization of biomass and xylitol production from xylose by yeasts has been studied by using batch and continuous cultures (3,20). However, industrial substrates, such as the hemicellulose hydrolysates obtained from several sources, are usually mixtures of hexoses and pentoses.…”

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confidence: 99%

Transport and Utilization of Hexoses and Pentoses in the Halotolerant Yeast Debaryomyces hansenii

Nobre

Lucas

Leão

1999

Appl Environ Microbiol

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Debaryomyces hansenii is a yeast species that is known for its halotolerance. This organism has seldom been mentioned as a pentose consumer. In the present work, a strain of this species was investigated with respect to the utilization of pentoses and hexoses in mixtures and as single carbon sources. Growth parameters were calculated for batch aerobic cultures containing pentoses, hexoses, and mixtures of both types of sugars. Growth on pentoses was slower than growth on hexoses, but the values obtained for biomass yields were very similar with the two types of sugars. Furthermore, when mixtures of two sugars were used, a preference for one carbon source did not inhibit consumption of the other. Glucose and xylose were transported by cells grown on glucose via a specific low-affinity facilitated diffusion system. Cells derepressed by growth on xylose had two distinct high-affinity transport systems for glucose and xylose. The sensitivity of labeled glucose and xylose transport to dissipation of the transmembrane proton gradient by the protonophore carbonyl cyanidem-chlorophenylhydrazone allowed us to consider these transport systems as proton symports, although the cells displayed sugar-associated proton uptake exclusively in the presence of NaCl or KCl. When the V max values of transport systems for glucose and xylose were compared with glucose- and xylose-specific consumption rates during growth on either sugar, it appeared that transport did not limit the growth rate.

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“…The estimation of these parameters for pure cultures is traditionally performed through batch or chemostat culture. Among these two, the chemostat is considered the most suitable method for determining substrate affinity constant (K S , Duarte et al, 1994). It consists in measuring the residual limiting substrate concentration for different dilution rates applied to a chemostat.…”

Section: Introductionmentioning

confidence: 99%

Determination of Kinetic and Stoichiometric Parameters of Pseudomonas putida F1 by Chemostat and In Situ Pulse Respirometry

Oliveira

Ordaz

Alba

et al. 2009

Chemical Product and Process Modeling

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The applicability of pulse respirometry, for the estimation of kinetic and stoichiometric parameters in pure cultures was evaluated by comparison with traditional chemostat method. Pseudomonas putida F1 was cultured in a continuous stirred tank reactor, using glucose as sole carbon source. The reactor was operated under steady-state with six dilution rates, ranging from 0.06 to 0.35 h -1 . Substrate and biomass concentration were measured and used to estimate kinetic and stoichiometric parameters, according to the Monod model. An in situ respirometry method was also applied to the reactor, with the injection of pulses of glucose from 19 to 97 mg L -1 . The respirograms obtained were used to estimate the kinetic and stoichiometric parameters according to ASM1 and ASM3 models. No significance difference was observed between parameters estimated by chemostat and respirometric methods. The glucose affinity constant was from 0.4 to 0.7 mg L -1 , the maximum specific growth rate was from varying from 0.14 to 0.20 h -1 , and the growth yield was from 0.41 to 0.67. These results confirm that in situ pulse respirometry is a suitable method for kinetic and stoichiometric parameters estimation.

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Determination of the kinetic parameters in continuous cultivation byDebaryomyces hansenii grown on D-xylose

Cited by 11 publications

References 9 publications

Phosphate limitation stress induces xylitol overproduction by Debaryomyces hansenii

Phosphate limitation stress induces xylitol overproduction by Debaryomyces hansenii

Transport and Utilization of Hexoses and Pentoses in the Halotolerant Yeast Debaryomyces hansenii

Determination of Kinetic and Stoichiometric Parameters of Pseudomonas putida F1 by Chemostat and In Situ Pulse Respirometry

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