Metabolic Flux Analysis of Candida tropicalis Growing on Xylose in an Oxygen-Limited Chemostat

Granström, Tom

doi:10.1006/mben.2002.0230

Cited by 29 publications

(17 citation statements)

References 37 publications

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“…A report suggests that xylose-grown Candida contains enzyme activities participating in gluconeogenesis, which places xylose amongst the nonfermentable substrates (Granstro¨m et al, 2002). This is supported also by our own, yet unpublished results in S. cerevisiae.…”

Section: The Effect Of Glucose At the Uptakesupporting

confidence: 78%

Metabolic flux analysis of xylose metabolism in recombinant Saccharomyces cerevisiae using continuous culture

Pitkänen

Aristidou

Salusjärvi

et al. 2003

Metabolic Engineering

108

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This study focused on elucidating metabolism of xylose in a Saccharomyces cerevisiae strain that overexpresses xylose reductase and xylitol dehydrogenase from Pichia stipitis, as well as the endogenous xylulokinase. The influence of xylose on overall metabolism was examined supplemented with low glucose levels with emphasis on two potential bottlenecks; cofactor requirements and xylose uptake. Results of metabolic flux analysis in continuous cultivations show changes in central metabolism due to the cofactor imbalance imposed by the two-step oxidoreductase reaction of xylose to xylulose. A comparison between cultivations on 27:3 g/L xylose-glucose mixture and 10 g/L glucose revealed that the NADPH-generating flux from glucose-6-phosphate to ribulose-5-phosphate was almost tenfold higher on xylose-glucose mixture and due to the loss of carbon in that pathway the total flux to pyruvate was only around 60% of that on glucose. As a consequence also the fluxes in the citric acid cycle were reduced to around 60%. As the glucose level was decreased to 0.1 g/L the fluxes to pyruvate and in the citric acid cycle were further reduced to 30% and 20%, respectively. The results from in vitro and in vivo xylose uptake measurements showed that the specific xylose uptake rate was highest at the lowest glucose level, 0.1 g/L.

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Section: The Effect Of Glucose At the Uptakesupporting

confidence: 78%

Metabolic flux analysis of xylose metabolism in recombinant Saccharomyces cerevisiae using continuous culture

Pitkänen

Aristidou

Salusjärvi

et al. 2003

Metabolic Engineering

108

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“…Aeration affects the redox balance of xylose-assimilating yeast (6). Oxygen limitation results in increased intracellular NADH levels, which in turn leads to increased xylitol production by C. tropicalis (7,17). Previous studies used the two-stage batch culture technique, controlling aeration to enhance the productivity and yield of xylitol (16).…”

Section: Discussionmentioning

confidence: 99%

Production of Xylitol from d -Xylose by a Xylitol Dehydrogenase Gene-Disrupted Mutant of Candida tropicalis

Kim

2006

Appl Environ Microbiol

103

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Xylitol dehydrogenase (XDH) is one of the key enzymes in D-xylose metabolism, catalyzing the oxidation of xylitol to D-xylulose. Two copies of the XYL2 gene encoding XDH in the diploid yeast Candida tropicalis were sequentially disrupted using the Ura-blasting method. The XYL2-disrupted mutant, BSXDH-3, did not grow on a minimal medium containing D-xylose as a sole carbon source. An enzyme assay experiment indicated that BSXDH-3 lost apparently all XDH activity. Xylitol production by BSXDH-3 was evaluated using a xylitol fermentation medium with glucose as a cosubstrate. As glucose was found to be an insufficient cosubstrate, various carbon sources were screened for efficient cofactor regeneration, and glycerol was found to be the best cosubstrate. BSXDH-3 produced xylitol with a volumetric productivity of 3.23 g liter ؊1 h ؊1 , a specific productivity of 0.76 g g ؊1 h ؊1 , and a xylitol yield of 98%. This is the first report of gene disruption of C. tropicalis for enhancing the efficiency of xylitol production.

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“…XR reduces xylose to xylitol, XDH oxidizes xylitol to xylulose which is then phosphorylated to xylulose-5-phosphate by XK. Xylulose-5-phosphate is then metabolized through the pentose phosphate pathway into ethanol [8,21]. Figure 2 shows the CABH fermentation by K. marxianus CE025 at 40°C, 200 rpm, and initial pH 4.5.…”

Section: Ethanol Production By Kluyveromyces Marxianus Ce025mentioning

confidence: 99%

Cashew apple bagasse as a source of sugars for ethanol production by Kluyveromyces marxianus CE025

Rocha

Rodrigues

Melo

et al. 2010

J Ind Microbiol Biotechnol

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The potential of cashew apple bagasse as a source of sugars for ethanol production by Kluyveromyces marxianus CE025 was evaluated in this work. This strain was preliminarily cultivated in a synthetic medium containing glucose and xylose and was able to produce ethanol and xylitol at pH 4.5. Next, cashew apple bagasse hydrolysate (CABH) was prepared by a diluted sulfuric acid pretreatment and used as fermentation media. This hydrolysate is rich in glucose, xylose, and arabinose and contains traces of formic acid and acetic acid. In batch fermentations of CABH at pH 4.5, the strain produced only ethanol. The effects of temperature on the kinetic parameters of ethanol fermentation by K. marxianus CE025 using CABH were also evaluated. Maximum specific growth rate (μ(max)), overall yields of ethanol based on glucose consumption [Formula: see text] and based on glucose + xylose consumption (Y ( P/S )), overall yield of ethanol based on biomass (Y ( P/X )), and ethanol productivity (P (E)) were determined as a function of temperature. Best results of ethanol production were achieved at 30°C, which is also quite close to the optimum temperature for the formation of biomass. The process yielded 12.36 ± 0.06 g l(-1) of ethanol with a volumetric production rate of 0.257 ± 0.002 g l(-1) h(-1) and an ethanol yield of 0.417 ± 0.003 g g(-1) glucose.

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Metabolic Flux Analysis of Candida tropicalis Growing on Xylose in an Oxygen-Limited Chemostat

Cited by 29 publications

References 37 publications

Metabolic flux analysis of xylose metabolism in recombinant Saccharomyces cerevisiae using continuous culture

Metabolic flux analysis of xylose metabolism in recombinant Saccharomyces cerevisiae using continuous culture

Production of Xylitol from d -Xylose by a Xylitol Dehydrogenase Gene-Disrupted Mutant of Candida tropicalis

Cashew apple bagasse as a source of sugars for ethanol production by Kluyveromyces marxianus CE025

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