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Saccharomyces cerevisiae transcriptional reprograming due to bacterial contamination during industrial scale bioethanol production.

Carvalho-Netto OV, Carazzolle MF, Mofatto LS, Teixeira PJ, Noronha MF, Calderón LA, Mieczkowski PA, Argueso JL, Pereira GA - Microb. Cell Fact. (2015)

Bottom Line: The bioethanol production system used in Brazil is based on the fermentation of sucrose from sugarcane feedstock by highly adapted strains of the yeast Saccharomyces cerevisiae.The formation of such particles is undesirable because it slows the fermentation kinetics and reduces the overall bioethanol yield.In this study, we investigated the molecular physiology of one of the main S. cerevisiae strains used in Brazilian bioethanol production, PE-2, under two contrasting conditions: typical fermentation, when most yeast cells are in suspension, and co-aggregated fermentation.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, SP, Brazil. osmar@lge.ibi.unicamp.br.

ABSTRACT

Background: The bioethanol production system used in Brazil is based on the fermentation of sucrose from sugarcane feedstock by highly adapted strains of the yeast Saccharomyces cerevisiae. Bacterial contaminants present in the distillery environment often produce yeast-bacteria cellular co-aggregation particles that resemble yeast-yeast cell adhesion (flocculation). The formation of such particles is undesirable because it slows the fermentation kinetics and reduces the overall bioethanol yield.

Results: In this study, we investigated the molecular physiology of one of the main S. cerevisiae strains used in Brazilian bioethanol production, PE-2, under two contrasting conditions: typical fermentation, when most yeast cells are in suspension, and co-aggregated fermentation. The transcriptional profile of PE-2 was assessed by RNA-seq during industrial scale fed-batch fermentation. Comparative analysis between the two conditions revealed transcriptional profiles that were differentiated primarily by a deep gene repression in the co-aggregated samples. The data also indicated that Lactobacillus fermentum was likely the main bacterial species responsible for cellular co-aggregation and for the high levels of organic acids detected in the samples.

Conclusions: Here, we report the high-resolution gene expression profiling of strain PE-2 during industrial-scale fermentations and the transcriptional reprograming observed under co-aggregation conditions. This dataset constitutes an important resource that can provide support for further development of this key yeast biocatalyst.

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Related in: MedlinePlus

Kinetics of production and consumption of major compounds examined during the fermentations. Content in g/L of: A- ethanol; B- glycerol; C- sucrose; D- C6 sugars (glucose and fructose); E- lactic acid; and F- acetic acid. The compounds were measured with HPLC equipment using samples collected during the fermentations. FL - flocculated fermentation: black lines; TF - typical fermentation: gray lines. Standard deviation bars were obtained using three technical replicates for each time point. Please, note that the same time points between the two fermentation conditions (eg. FL3 vs. TF3) are not directly comparable in isolation, as they do not necessarily correspond to the same stage along each fermentation.
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Fig2: Kinetics of production and consumption of major compounds examined during the fermentations. Content in g/L of: A- ethanol; B- glycerol; C- sucrose; D- C6 sugars (glucose and fructose); E- lactic acid; and F- acetic acid. The compounds were measured with HPLC equipment using samples collected during the fermentations. FL - flocculated fermentation: black lines; TF - typical fermentation: gray lines. Standard deviation bars were obtained using three technical replicates for each time point. Please, note that the same time points between the two fermentation conditions (eg. FL3 vs. TF3) are not directly comparable in isolation, as they do not necessarily correspond to the same stage along each fermentation.

Mentions: Analysis of the chemical composition of the collected samples revealed four significant differences in the kinetics of flocculated versus typical fermentation (Figure 2). Compared to the TF samples, the FL samples had (i) lower final ethanol titer, (ii) lower glycerol production, (iii) higher lactic and acetic acid concentrations, and (iv) slower rate of sucrose hydrolysis.Figure 2


Saccharomyces cerevisiae transcriptional reprograming due to bacterial contamination during industrial scale bioethanol production.

Carvalho-Netto OV, Carazzolle MF, Mofatto LS, Teixeira PJ, Noronha MF, Calderón LA, Mieczkowski PA, Argueso JL, Pereira GA - Microb. Cell Fact. (2015)

Kinetics of production and consumption of major compounds examined during the fermentations. Content in g/L of: A- ethanol; B- glycerol; C- sucrose; D- C6 sugars (glucose and fructose); E- lactic acid; and F- acetic acid. The compounds were measured with HPLC equipment using samples collected during the fermentations. FL - flocculated fermentation: black lines; TF - typical fermentation: gray lines. Standard deviation bars were obtained using three technical replicates for each time point. Please, note that the same time points between the two fermentation conditions (eg. FL3 vs. TF3) are not directly comparable in isolation, as they do not necessarily correspond to the same stage along each fermentation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4318157&req=5

Fig2: Kinetics of production and consumption of major compounds examined during the fermentations. Content in g/L of: A- ethanol; B- glycerol; C- sucrose; D- C6 sugars (glucose and fructose); E- lactic acid; and F- acetic acid. The compounds were measured with HPLC equipment using samples collected during the fermentations. FL - flocculated fermentation: black lines; TF - typical fermentation: gray lines. Standard deviation bars were obtained using three technical replicates for each time point. Please, note that the same time points between the two fermentation conditions (eg. FL3 vs. TF3) are not directly comparable in isolation, as they do not necessarily correspond to the same stage along each fermentation.
Mentions: Analysis of the chemical composition of the collected samples revealed four significant differences in the kinetics of flocculated versus typical fermentation (Figure 2). Compared to the TF samples, the FL samples had (i) lower final ethanol titer, (ii) lower glycerol production, (iii) higher lactic and acetic acid concentrations, and (iv) slower rate of sucrose hydrolysis.Figure 2

Bottom Line: The bioethanol production system used in Brazil is based on the fermentation of sucrose from sugarcane feedstock by highly adapted strains of the yeast Saccharomyces cerevisiae.The formation of such particles is undesirable because it slows the fermentation kinetics and reduces the overall bioethanol yield.In this study, we investigated the molecular physiology of one of the main S. cerevisiae strains used in Brazilian bioethanol production, PE-2, under two contrasting conditions: typical fermentation, when most yeast cells are in suspension, and co-aggregated fermentation.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, SP, Brazil. osmar@lge.ibi.unicamp.br.

ABSTRACT

Background: The bioethanol production system used in Brazil is based on the fermentation of sucrose from sugarcane feedstock by highly adapted strains of the yeast Saccharomyces cerevisiae. Bacterial contaminants present in the distillery environment often produce yeast-bacteria cellular co-aggregation particles that resemble yeast-yeast cell adhesion (flocculation). The formation of such particles is undesirable because it slows the fermentation kinetics and reduces the overall bioethanol yield.

Results: In this study, we investigated the molecular physiology of one of the main S. cerevisiae strains used in Brazilian bioethanol production, PE-2, under two contrasting conditions: typical fermentation, when most yeast cells are in suspension, and co-aggregated fermentation. The transcriptional profile of PE-2 was assessed by RNA-seq during industrial scale fed-batch fermentation. Comparative analysis between the two conditions revealed transcriptional profiles that were differentiated primarily by a deep gene repression in the co-aggregated samples. The data also indicated that Lactobacillus fermentum was likely the main bacterial species responsible for cellular co-aggregation and for the high levels of organic acids detected in the samples.

Conclusions: Here, we report the high-resolution gene expression profiling of strain PE-2 during industrial-scale fermentations and the transcriptional reprograming observed under co-aggregation conditions. This dataset constitutes an important resource that can provide support for further development of this key yeast biocatalyst.

Show MeSH
Related in: MedlinePlus