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Encapsulation-induced stress helps Saccharomyces cerevisiae resist convertible Lignocellulose derived inhibitors.

Westman JO, Manikondu RB, Franzén CJ, Taherzadeh MJ - Int J Mol Sci (2012)

Bottom Line: It was shown that encapsulation increased the tolerance against readily convertible furan aldehyde inhibitors and to dilute acid spruce hydrolysate, but not to organic acid inhibitors that cannot be metabolized anaerobically.Gene expression analysis showed that the protective effect arising from the encapsulation is evident also on the transcriptome level, as the expression of the stress-related genes YAP1, ATR1 and FLR1 was induced upon encapsulation.The transcript levels were increased due to encapsulation already in the medium without added inhibitors, indicating that the cells sensed low stress level arising from the encapsulation itself.

View Article: PubMed Central - PubMed

Affiliation: School of Engineering, University of Borås, 501 90 Borås, Sweden; E-Mails: rameshmanikondu@hotmail.com (R.B.M.); mohammad.taherzadeh@hb.se (M.J.T.) ; Chemical and Biological Engineering-Industrial biotechnology, Chalmers University of Technology, 412 96 Göteborg, Sweden; E-Mail: franzen@chalmers.se.

ABSTRACT
The ability of macroencapsulated Saccharomyces cerevisiae CBS8066 to withstand readily and not readily in situ convertible lignocellulose-derived inhibitors was investigated in anaerobic batch cultivations. It was shown that encapsulation increased the tolerance against readily convertible furan aldehyde inhibitors and to dilute acid spruce hydrolysate, but not to organic acid inhibitors that cannot be metabolized anaerobically. Gene expression analysis showed that the protective effect arising from the encapsulation is evident also on the transcriptome level, as the expression of the stress-related genes YAP1, ATR1 and FLR1 was induced upon encapsulation. The transcript levels were increased due to encapsulation already in the medium without added inhibitors, indicating that the cells sensed low stress level arising from the encapsulation itself. We present a model, where the stress response is induced by nutrient limitation, that this helps the cells to cope with the increased stress added by a toxic medium, and that superficial cells in the capsules degrade convertible inhibitors, alleviating the inhibition for the cells deeper in the capsule.

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Hexose (A) and ethanol (B) concentrations during anaerobic batch cultivations using encapsulated yeast in defined glucose medium (DGM) (⋄), DGM with furan aldehydes (□), DGM with carboxylic acids (△), and hydrolysate (×).
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f1-ijms-13-11881: Hexose (A) and ethanol (B) concentrations during anaerobic batch cultivations using encapsulated yeast in defined glucose medium (DGM) (⋄), DGM with furan aldehydes (□), DGM with carboxylic acids (△), and hydrolysate (×).

Mentions: Glucose consumption and ethanol production profiles from the anaerobic batch cultivations of encapsulated yeast are presented in Figure 1 and final yields of important metabolites in Table 1. The chitosan-alginate capsules were successful in making the yeast able to ferment the toxic hydrolysate in anaerobic batch cultures (Figure 1). Encapsulation also helped against the mix of furan aldehydes (furfural and HMF), resulting in only slightly slower glucose consumption and ethanol production than what was observed for medium without inhibitors (Figure 1). The consumption rate of the first 12 g/L glucose was approximately 80% of the rate in the non-inhibiting medium. We hypothesize that the high local cell density inside the capsules facilitates a fast conversion of the inhibitors entering the capsule, thus keeping the local inhibitor concentration at a low level. By the end of the cultivations, the overall consumption of furfural and HMF was generally higher for the encapsulated cells than for free cells in similar conditions (Table 2), although the free cells were also able to convert most of the furan aldehydes in the defined medium and some in the hydrolysate medium.


Encapsulation-induced stress helps Saccharomyces cerevisiae resist convertible Lignocellulose derived inhibitors.

Westman JO, Manikondu RB, Franzén CJ, Taherzadeh MJ - Int J Mol Sci (2012)

Hexose (A) and ethanol (B) concentrations during anaerobic batch cultivations using encapsulated yeast in defined glucose medium (DGM) (⋄), DGM with furan aldehydes (□), DGM with carboxylic acids (△), and hydrolysate (×).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3472781&req=5

f1-ijms-13-11881: Hexose (A) and ethanol (B) concentrations during anaerobic batch cultivations using encapsulated yeast in defined glucose medium (DGM) (⋄), DGM with furan aldehydes (□), DGM with carboxylic acids (△), and hydrolysate (×).
Mentions: Glucose consumption and ethanol production profiles from the anaerobic batch cultivations of encapsulated yeast are presented in Figure 1 and final yields of important metabolites in Table 1. The chitosan-alginate capsules were successful in making the yeast able to ferment the toxic hydrolysate in anaerobic batch cultures (Figure 1). Encapsulation also helped against the mix of furan aldehydes (furfural and HMF), resulting in only slightly slower glucose consumption and ethanol production than what was observed for medium without inhibitors (Figure 1). The consumption rate of the first 12 g/L glucose was approximately 80% of the rate in the non-inhibiting medium. We hypothesize that the high local cell density inside the capsules facilitates a fast conversion of the inhibitors entering the capsule, thus keeping the local inhibitor concentration at a low level. By the end of the cultivations, the overall consumption of furfural and HMF was generally higher for the encapsulated cells than for free cells in similar conditions (Table 2), although the free cells were also able to convert most of the furan aldehydes in the defined medium and some in the hydrolysate medium.

Bottom Line: It was shown that encapsulation increased the tolerance against readily convertible furan aldehyde inhibitors and to dilute acid spruce hydrolysate, but not to organic acid inhibitors that cannot be metabolized anaerobically.Gene expression analysis showed that the protective effect arising from the encapsulation is evident also on the transcriptome level, as the expression of the stress-related genes YAP1, ATR1 and FLR1 was induced upon encapsulation.The transcript levels were increased due to encapsulation already in the medium without added inhibitors, indicating that the cells sensed low stress level arising from the encapsulation itself.

View Article: PubMed Central - PubMed

Affiliation: School of Engineering, University of Borås, 501 90 Borås, Sweden; E-Mails: rameshmanikondu@hotmail.com (R.B.M.); mohammad.taherzadeh@hb.se (M.J.T.) ; Chemical and Biological Engineering-Industrial biotechnology, Chalmers University of Technology, 412 96 Göteborg, Sweden; E-Mail: franzen@chalmers.se.

ABSTRACT
The ability of macroencapsulated Saccharomyces cerevisiae CBS8066 to withstand readily and not readily in situ convertible lignocellulose-derived inhibitors was investigated in anaerobic batch cultivations. It was shown that encapsulation increased the tolerance against readily convertible furan aldehyde inhibitors and to dilute acid spruce hydrolysate, but not to organic acid inhibitors that cannot be metabolized anaerobically. Gene expression analysis showed that the protective effect arising from the encapsulation is evident also on the transcriptome level, as the expression of the stress-related genes YAP1, ATR1 and FLR1 was induced upon encapsulation. The transcript levels were increased due to encapsulation already in the medium without added inhibitors, indicating that the cells sensed low stress level arising from the encapsulation itself. We present a model, where the stress response is induced by nutrient limitation, that this helps the cells to cope with the increased stress added by a toxic medium, and that superficial cells in the capsules degrade convertible inhibitors, alleviating the inhibition for the cells deeper in the capsule.

Show MeSH
Related in: MedlinePlus