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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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Time course of diffusion through the membrane of the chitosan-alginate capsules; glucose (), HMF (), furfural (), levulinic acid (), acetic acid () and formic acid (). The lines show the profile of diffusion according to Equation 1 for the respective compounds.
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f4-ijms-13-11881: Time course of diffusion through the membrane of the chitosan-alginate capsules; glucose (), HMF (), furfural (), levulinic acid (), acetic acid () and formic acid (). The lines show the profile of diffusion according to Equation 1 for the respective compounds.

Mentions: A possible explanation for the observed differences in tolerance towards the furan aldehyde and carboxylic acid inhibitors could be differences in their diffusivity into the capsules. This was the case for the hydrophobic inhibitor limonene, which could not diffuse into the capsules [27]. The diffusion of glucose and the inhibitors furfural, HMF, acetic acid, formic acid and levulinic acid into the capsules was therefore investigated. The capsules used in the test did not contain yeast, and were equilibrated in water prior to the test. The diffusion of the compounds into the capsules was monitored for 120 min (Figure 4), after which water was added and the diffusion out of the capsules was monitored. Although the acids had a somewhat faster diffusion into the capsules than the furan aldehydes (Table 3), it can most likely be ruled out as a reason for the increased tolerance towards furan aldehydes, since the diffusion was rather fast for all tested compounds. The diffusion rate was markedly faster than what has previously been reported for Ca-alginate capsules, identical to the capsules used in this study, except for the additional chitosan incorporation [8,15]. The results show that the chitosan treatment of the capsules resulted in a faster diffusion of glucose, HMF, furfural and acetate, with 95 ± 3% of the final concentrations already after 14 min, compared to the reported 90 ± 3% after 20 min without chitosan treatment [8]. The volumetric mass transfer coefficient for glucose into the chitosan-alginate capsules was calculated to 10.04 (cm3/min), which can be compared with a value of 6.28 (cm3/min) calculated for cell-free Ca-alginate capsules in a similar experimental setup [15]. The volumetric mass transfer coefficients for the compounds tested was proportional to the molecular weight of the compound (Table 3), with lighter molecules diffusing faster into the capsules. The diffusion out of the capsules was slightly slower than the diffusion in, (96 ± 3% of the final concentrations after 20 min), likely due to the slower internal mixing rate inside the capsules. The tendency towards an over-estimation of the glucose concentration at early time points by Equation 1, both in Figure 4 and a previous work [15], is hypothesized to come from osmosis of water from the capsules to the surrounding solution, because of the high solute concentration, shrinking the capsules (also noticed by visual observation), and thus lowering the measured solute levels. As the solute concentrations are leveled out, the capsules regain their original shape.


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

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

Time course of diffusion through the membrane of the chitosan-alginate capsules; glucose (), HMF (), furfural (), levulinic acid (), acetic acid () and formic acid (). The lines show the profile of diffusion according to Equation 1 for the respective compounds.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4-ijms-13-11881: Time course of diffusion through the membrane of the chitosan-alginate capsules; glucose (), HMF (), furfural (), levulinic acid (), acetic acid () and formic acid (). The lines show the profile of diffusion according to Equation 1 for the respective compounds.
Mentions: A possible explanation for the observed differences in tolerance towards the furan aldehyde and carboxylic acid inhibitors could be differences in their diffusivity into the capsules. This was the case for the hydrophobic inhibitor limonene, which could not diffuse into the capsules [27]. The diffusion of glucose and the inhibitors furfural, HMF, acetic acid, formic acid and levulinic acid into the capsules was therefore investigated. The capsules used in the test did not contain yeast, and were equilibrated in water prior to the test. The diffusion of the compounds into the capsules was monitored for 120 min (Figure 4), after which water was added and the diffusion out of the capsules was monitored. Although the acids had a somewhat faster diffusion into the capsules than the furan aldehydes (Table 3), it can most likely be ruled out as a reason for the increased tolerance towards furan aldehydes, since the diffusion was rather fast for all tested compounds. The diffusion rate was markedly faster than what has previously been reported for Ca-alginate capsules, identical to the capsules used in this study, except for the additional chitosan incorporation [8,15]. The results show that the chitosan treatment of the capsules resulted in a faster diffusion of glucose, HMF, furfural and acetate, with 95 ± 3% of the final concentrations already after 14 min, compared to the reported 90 ± 3% after 20 min without chitosan treatment [8]. The volumetric mass transfer coefficient for glucose into the chitosan-alginate capsules was calculated to 10.04 (cm3/min), which can be compared with a value of 6.28 (cm3/min) calculated for cell-free Ca-alginate capsules in a similar experimental setup [15]. The volumetric mass transfer coefficients for the compounds tested was proportional to the molecular weight of the compound (Table 3), with lighter molecules diffusing faster into the capsules. The diffusion out of the capsules was slightly slower than the diffusion in, (96 ± 3% of the final concentrations after 20 min), likely due to the slower internal mixing rate inside the capsules. The tendency towards an over-estimation of the glucose concentration at early time points by Equation 1, both in Figure 4 and a previous work [15], is hypothesized to come from osmosis of water from the capsules to the surrounding solution, because of the high solute concentration, shrinking the capsules (also noticed by visual observation), and thus lowering the measured solute levels. As the solute concentrations are leveled out, the capsules regain their original shape.

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