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Induction of D-xylose uptake and expression of NAD(P)H-linked xylose reductase and NADP + -linked xylitol dehydrogenase in the oleaginous microalga Chlorella sorokiniana.

Zheng Y, Yu X, Li T, Xiong X, Chen S - Biotechnol Biofuels (2014)

Bottom Line: The uptake of D-xylose activated the related metabolic pathway, and the activities of a NAD(P)H-linked xylose reductase (XR) and a unique NADP(+)-linked xylitol dehydrogenase (XDH) were detected in C. sorokiniana.The uptake of D-xylose subsequently activated the expression of key catalytic enzymes that enabled D-xylose entering central metabolism.Results of this research are useful to better understand the D-xylose metabolic pathway in the microalga C. sorokiniana and provide a target for genetic engineering to improve D-xylose utilization for microalgal lipid production.

View Article: PubMed Central - PubMed

Affiliation: LJ Smith 258, Biological Systems Engineering, Washington State University, Pullman, WA 99164 USA.

ABSTRACT

Background: The heterotrophic and mixotrophic culture of oleaginous microalgae is a promising process to produce biofuel feedstock due to the advantage of fast growth. Various organic carbons have been explored for this application. However, despite being one of the most abundant and economical sugar resources in nature, D-xylose has never been demonstrated as a carbon source for wild-type microalgae. The purpose of the present work was to identify the feasibility of D-xylose utilization by the oleaginous microalga Chlorella sorokiniana.

Results: The sugar uptake kinetic analysis was performed with (14)C-labeled sugars and the data showed that the D-glucose induced algal cells (the alga was heterotrophically grown on D-glucose and then harvested as D-glucose induced cells) exhibited a remarkably increased D-xylose uptake rate. The maximum D-xylose transport rate was 3.8 nmol min(-1) mg(-1) dry cell weight (DCW) with K m value of 6.8 mM. D-xylose uptake was suppressed in the presence of D-glucose, D-galactose and D-fructose but not L-arabinose and D-ribose. The uptake of D-xylose activated the related metabolic pathway, and the activities of a NAD(P)H-linked xylose reductase (XR) and a unique NADP(+)-linked xylitol dehydrogenase (XDH) were detected in C. sorokiniana. Compared with the culture in the dark, the consumption of D-xylose increased 2 fold under light but decreased to the same level with addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), indicating that extra chemical energy from the light-dependent reaction contributed the catabolism of D-xylose for C. sorokiniana.

Conclusions: An inducible D-xylose transportation system and a related metabolic pathway were discovered for microalga for the first time. The transportation of D-xylose across the cell membrane of C. sorokiniana could be realized by an inducible hexose symporter. The uptake of D-xylose subsequently activated the expression of key catalytic enzymes that enabled D-xylose entering central metabolism. Results of this research are useful to better understand the D-xylose metabolic pathway in the microalga C. sorokiniana and provide a target for genetic engineering to improve D-xylose utilization for microalgal lipid production.

No MeSH data available.


Related in: MedlinePlus

D-xylose consumption (dark column) and xylitol production (white column) byC. sorokiniana. The induced algal cells were washed with sterile distilled water and re-suspended in 8 mg DCW per mL in 50 mL minimal medium supplemented with 5 mM KNO 3 and 40 mM D-xylose under different conditions for 24 hours.
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Fig3: D-xylose consumption (dark column) and xylitol production (white column) byC. sorokiniana. The induced algal cells were washed with sterile distilled water and re-suspended in 8 mg DCW per mL in 50 mL minimal medium supplemented with 5 mM KNO 3 and 40 mM D-xylose under different conditions for 24 hours.

Mentions: Figure 3 shows D-xylose consumption and xylitol production by the induced C. sorokiniana under different conditions. The highest D-xylose consumption of 19.1 mM was observed for the cultures with light. C. sorokiniana also had the capability to utilize D-xylose in the dark but the consumption was more than 2-fold lower compared with the cultures under light. The stimulation of D-xylose utilization by light was diminished in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), evidenced by a comparable D-xylose consumption with the cultures in the dark. However, DCMU did not play a significant inhibitory role in D-xylose utilization in the dark conditions. Xylitol was formed during the growth in all the cultures. C. sorokiniana converted 50 to 60% of the consumed D-xylose to xylitol.Figure 3


Induction of D-xylose uptake and expression of NAD(P)H-linked xylose reductase and NADP + -linked xylitol dehydrogenase in the oleaginous microalga Chlorella sorokiniana.

Zheng Y, Yu X, Li T, Xiong X, Chen S - Biotechnol Biofuels (2014)

D-xylose consumption (dark column) and xylitol production (white column) byC. sorokiniana. The induced algal cells were washed with sterile distilled water and re-suspended in 8 mg DCW per mL in 50 mL minimal medium supplemented with 5 mM KNO 3 and 40 mM D-xylose under different conditions for 24 hours.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4195881&req=5

Fig3: D-xylose consumption (dark column) and xylitol production (white column) byC. sorokiniana. The induced algal cells were washed with sterile distilled water and re-suspended in 8 mg DCW per mL in 50 mL minimal medium supplemented with 5 mM KNO 3 and 40 mM D-xylose under different conditions for 24 hours.
Mentions: Figure 3 shows D-xylose consumption and xylitol production by the induced C. sorokiniana under different conditions. The highest D-xylose consumption of 19.1 mM was observed for the cultures with light. C. sorokiniana also had the capability to utilize D-xylose in the dark but the consumption was more than 2-fold lower compared with the cultures under light. The stimulation of D-xylose utilization by light was diminished in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), evidenced by a comparable D-xylose consumption with the cultures in the dark. However, DCMU did not play a significant inhibitory role in D-xylose utilization in the dark conditions. Xylitol was formed during the growth in all the cultures. C. sorokiniana converted 50 to 60% of the consumed D-xylose to xylitol.Figure 3

Bottom Line: The uptake of D-xylose activated the related metabolic pathway, and the activities of a NAD(P)H-linked xylose reductase (XR) and a unique NADP(+)-linked xylitol dehydrogenase (XDH) were detected in C. sorokiniana.The uptake of D-xylose subsequently activated the expression of key catalytic enzymes that enabled D-xylose entering central metabolism.Results of this research are useful to better understand the D-xylose metabolic pathway in the microalga C. sorokiniana and provide a target for genetic engineering to improve D-xylose utilization for microalgal lipid production.

View Article: PubMed Central - PubMed

Affiliation: LJ Smith 258, Biological Systems Engineering, Washington State University, Pullman, WA 99164 USA.

ABSTRACT

Background: The heterotrophic and mixotrophic culture of oleaginous microalgae is a promising process to produce biofuel feedstock due to the advantage of fast growth. Various organic carbons have been explored for this application. However, despite being one of the most abundant and economical sugar resources in nature, D-xylose has never been demonstrated as a carbon source for wild-type microalgae. The purpose of the present work was to identify the feasibility of D-xylose utilization by the oleaginous microalga Chlorella sorokiniana.

Results: The sugar uptake kinetic analysis was performed with (14)C-labeled sugars and the data showed that the D-glucose induced algal cells (the alga was heterotrophically grown on D-glucose and then harvested as D-glucose induced cells) exhibited a remarkably increased D-xylose uptake rate. The maximum D-xylose transport rate was 3.8 nmol min(-1) mg(-1) dry cell weight (DCW) with K m value of 6.8 mM. D-xylose uptake was suppressed in the presence of D-glucose, D-galactose and D-fructose but not L-arabinose and D-ribose. The uptake of D-xylose activated the related metabolic pathway, and the activities of a NAD(P)H-linked xylose reductase (XR) and a unique NADP(+)-linked xylitol dehydrogenase (XDH) were detected in C. sorokiniana. Compared with the culture in the dark, the consumption of D-xylose increased 2 fold under light but decreased to the same level with addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), indicating that extra chemical energy from the light-dependent reaction contributed the catabolism of D-xylose for C. sorokiniana.

Conclusions: An inducible D-xylose transportation system and a related metabolic pathway were discovered for microalga for the first time. The transportation of D-xylose across the cell membrane of C. sorokiniana could be realized by an inducible hexose symporter. The uptake of D-xylose subsequently activated the expression of key catalytic enzymes that enabled D-xylose entering central metabolism. Results of this research are useful to better understand the D-xylose metabolic pathway in the microalga C. sorokiniana and provide a target for genetic engineering to improve D-xylose utilization for microalgal lipid production.

No MeSH data available.


Related in: MedlinePlus