The influence of pH and aeration rate on the fermentation of d-xylose by Candida shehatae

Sánchez, Sebastián; Bravo, Vicente; Castro, Eulógio; Moya, Alberto J.; Camacho, F.

doi:10.1016/s0141-0229(97)00008-2

Cited by 33 publications

(26 citation statements)

References 14 publications

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“…Finally, as shown by Sánchez et al (1997), pH o variations may affect yeast cell permeability and may cause some micronutrient to precipitate, thus becoming unavailable for assimilation.…”

Section: Effect Of Starting Ph On Xylitol Productionmentioning

confidence: 99%

Influence of temperature and pH on xylitol production from xylose by Debaryomyces hansenii

Converti

Domínguez

2001

Biotech & Bioengineering

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The production of xylitol from concentrated synthetic xylose solutions (S(o) = 130-135 g/L) by Debaryomyces hansenii was investigated at different pH and temperature values. At optimum starting pH (pH(o) = 5.5), T = 24 degrees C, and relatively low starting biomass levels (0.5-0.6 g(x)/L), 88% of xylose was utilized for xylitol production, the rest being preferentially fermented to ethanol (10%). Under these conditions, nearly 70% of initial carbon was recovered as xylitol, corresponding to final xylitol concentration of 91.9 g(P)/L, product yield on substrate of 0.81 g(P)/g(S), and maximum volumetric and specific productivities of 1.86 g(P)/L x h and 1.43 g(P)/g(x) x h, respectively. At higher and lower pH(o) values, respiration also became important, consuming up to 32% of xylose, while negligible amounts were utilized for cell growth (0.8-1.8%). The same approach extended to the effect of temperature on the metabolism of this yeast at pH(o) = 5.5 and higher biomass levels (1.4-3.0 g(x)/L) revealed that, at temperatures ranging from 32-37 degrees C, xylose was nearly completely consumed to produce xylitol, reaching a maximum volumetric productivity of 4.67 g(P)/L x h at 35 degrees C. Similarly, both respiration and ethanol fermentation became significant either at higher or at lower temperatures. Finally, to elucidate the kinetic mechanisms of both xylitol production and thermal inactivation of the system, the related thermodynamic parameters were estimated from the experimental data with the Arrhenius model: activation enthalpy and entropy were 57.7 kJ/mol and -0.152 kJ/mol x K for xylitol production and 187.3 kJ/mol and 0.054 kJ/mol x K for thermal inactivation, respectively.

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“…Finally, as shown by Sánchez et al (1997), pH o variations may affect yeast cell permeability and may cause some micronutrient to precipitate, thus becoming unavailable for assimilation.…”

Section: Effect Of Starting Ph On Xylitol Productionmentioning

confidence: 99%

Influence of temperature and pH on xylitol production from xylose by Debaryomyces hansenii

Converti

Domínguez

2001

Biotech & Bioengineering

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“…From eqn (1), by following the procedures described previously 11,21 it was possible to determine the speci®c rate of total substrate consumption (q s ) versus time for each yeast strain (see Table 2). The values obtained for the earlier times correspond to the phase during which D-glucose was utilised, while times of more than 25 h are characteristic of the stage when D-xylose was being consumed.…”

Section: Substrate Consumptionmentioning

confidence: 99%

“…From eqns (2) and (3), following the procedures described previously, 11,21 it was possible to determine the speci®c ethanol production rate versus time for each of the experiments. As mentioned above, ethanol is produced during two distinct phases of the culture, which are separated by a stage during which cell growth, substrate consumption and the formation of products are either stationary or very slight.…”

Section: Ethanol and Xylitol Productionmentioning

confidence: 99%

The fermentation of mixtures of D‐glucose and D‐xylose by Candida shehatae, Pichia stipitis or Pachysolen tannophilus to produce ethanol

Sánchez

Bravo

Castro

et al. 2002

J of Chemical Tech & Biotech

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The fermentation of mixtures of D-glucose and D-xylose by three non-traditional yeasts: Candida shehatae (ATCC 34887), Pachysolen tannophilus (ATCC 32691) and Pichia stipitis (ATCC 58376) have been studied to determine the optimal strain and initial culture conditions for the ef®cient production of ethanol. The comparison was made on the basis of maximum speci®c growth rate (m m ), biomass productivity, the speci®c rates of total substrate consumption (q s ) and ethanol production (q E ) and the overall yields of ethanol and xylitol. All the experiments were performed in stirred-tank batch reactors at a temperature of 30°C. The initial pH of the culture medium was 4.5. The highest values of m m (above 0.5 h À1 ) were obtained with P stipitis in cultures containing high concentrations of D-xylose. All three yeasts consumed the two monosaccharides in sequence, beginning with D-glucose. The values of q s diminished during the course of each experiment with all of the yeasts. The highest values of the speci®c rates of total substrate consumption and ethanol production were obtained with C shehatae (for t = 10 h, q s and q E were above 5 g g À1 h À1 and 2 g g À1 h À1, respectively), although the highest overall ethanol yields were fairly similar with all three yeasts, at around 0.4 g g À1.

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“…In the present study, a comparative analysis is made of the ethanol fermentation of different mixtures of the two main monosaccharides (D-glucose and D-xylose) in any lignocellulose hydrolysate, using the yeasts Pachysolen tannophilus and Candida shehatae under operating conditions tested for each yeast in previous works [9,11].…”

Section: Introductionmentioning

confidence: 99%

Comparative study of the fermentation of D-glucose/D-xylose mixtures with Pachysolen tannophilus and Candida shehatae

Sánchez

Bravo

Castro

et al. 1999

Bioprocess Engineering

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We have performed a comparative analysis of the fermentation of the solutions of the mixtures of D-glucose and D-xylose with the yeasts Pachysolen tannophilus (ATCC 32691) and Candida shehatae (ATCC 34887), with the aim of producing bioethanol. All the experiments were performed in a batch bioreactor, with a constant aeration level, temperature of 30°C, and a culture medium with an initial pH of 4.5. For both yeasts, the comparison was established on the basis of the following parameters: maximum speci®c growth rate, biomass productivity, speci®c rate of substrate consumption (q s ) and of ethanol production (q E ), and overall ethanol and xylitol yields. For the calculation of the speci®c rates of substrate consumption and ethanol production, differential and integral methods were applied to the kinetic data. From the experimental results, it is deduced that both Candida and Pachysolen sequentially consume the two substrates, ®rst D-glucose and then D-xylose. In both yeasts, the speci®c substrateconsumption rate diminished over each culture. The values q s and q E proved higher in Candida, although the higher ethanol yield was of the same order for both yeasts, close to 0.4 kg kg A1 .

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The influence of pH and aeration rate on the fermentation of d-xylose by Candida shehatae

Cited by 33 publications

References 14 publications

Influence of temperature and pH on xylitol production from xylose by Debaryomyces hansenii

Influence of temperature and pH on xylitol production from xylose by Debaryomyces hansenii

The fermentation of mixtures of D‐glucose and D‐xylose by Candida shehatae, Pichia stipitis or Pachysolen tannophilus to produce ethanol

Comparative study of the fermentation of D-glucose/D-xylose mixtures with Pachysolen tannophilus and Candida shehatae

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