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Characteristics of Saccharomyces cerevisiae yeasts exhibiting rough colonies and pseudohyphal morphology with respect to alcoholic fermentation.

Reis VR, Bassi AP, da Silva JC, Ceccato-Antonini SR - Braz. J. Microbiol. (2014)

Bottom Line: Among the native yeasts found in alcoholic fermentation, rough colonies associated with pseudohyphal morphology belonging to the species Saccharomyces cerevisiae are very common and undesirable during the process.The effects of acid treatment at different pH values on the growth of two strains ("52"--rough and "PE-02"--smooth) as well as batch fermentation tests with cell recycling and acid treatment of the cells were also evaluated.A fermentative efficiency as low as 60% was observed with the rough colony alone.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Tecnologia Agroindustrial e Socio-Economia Rural, Centro de Ciências Agrárias, Universidade Federal de São Carlos, Via Anhanguera, Araras, SP, Brazil.

ABSTRACT
Among the native yeasts found in alcoholic fermentation, rough colonies associated with pseudohyphal morphology belonging to the species Saccharomyces cerevisiae are very common and undesirable during the process. The aim of this work was to perform morphological and physiological characterisations of S. cerevisiae strains that exhibited rough and smooth colonies in an attempt to identify alternatives that could contribute to the management of rough colony yeasts in alcoholic fermentation. Characterisation tests for invasiveness in Agar medium, killer activity, flocculation and fermentative capacity were performed on 22 strains (11 rough and 11 smooth colonies). The effects of acid treatment at different pH values on the growth of two strains ("52"--rough and "PE-02"--smooth) as well as batch fermentation tests with cell recycling and acid treatment of the cells were also evaluated. Invasiveness in YPD Agar medium occurred at low frequency; ten of eleven rough yeasts exhibited flocculation; none of the strains showed killer activity; and the rough strains presented lower and slower fermentative capacities compared to the smooth strains in a 48-h cycle in a batch system with sugar cane juice. The growth of the rough strain was severely affected by the acid treatment at pH values of 1.0 and 1.5; however, the growth of the smooth strain was not affected. The fermentative efficiency in mixed fermentation (smooth and rough strains in the same cell mass proportion) did not differ from the efficiency obtained with the smooth strain alone, most likely because the acid treatment was conducted at pH 1.5 in a batch cell-recycle test. A fermentative efficiency as low as 60% was observed with the rough colony alone.

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Growth (cfu/mL) of two yeast strains of S. cerevisiae (52, in black, rough colony; PE-02, in grey, smooth colony), submitted to acid treatment with sulphuric acid at different pH values (1.0, 1.5 and 2.0) at 30 °C for 2 h at 160 rpm. The determination of cfu numbers (in YPD medium) was performed before the acid treatment, immediately after the acid treatment (0 h) and after 18 and 36 h of incubation of the treated cells in multiplication medium (sugar cane juice), at 30 °C and 160 rpm. Different capital and lowercase letters indicate significant differences (p < 0.05) among the treatments for the smooth colony and rough colony, respectively.
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f4-bmj-44-4-1121: Growth (cfu/mL) of two yeast strains of S. cerevisiae (52, in black, rough colony; PE-02, in grey, smooth colony), submitted to acid treatment with sulphuric acid at different pH values (1.0, 1.5 and 2.0) at 30 °C for 2 h at 160 rpm. The determination of cfu numbers (in YPD medium) was performed before the acid treatment, immediately after the acid treatment (0 h) and after 18 and 36 h of incubation of the treated cells in multiplication medium (sugar cane juice), at 30 °C and 160 rpm. Different capital and lowercase letters indicate significant differences (p < 0.05) among the treatments for the smooth colony and rough colony, respectively.

Mentions: For this test, the strains 17 (smooth) and 52 (rough) were chosen to verify the effect of acid treatment on their growth. The first strain (PE-02), is a yeast strain selected for its dominance and persistence throughout the entire harvest season (Basso et al., 2008) and for its high resistance to low pH (Reis 2011); the second strain was chosen because it has a high flocculation rate, as described above, and had resistance to high sugar concentrations and sensitivity to low pH (Reis 2011). The results showed that the rough strain was severely affected by pH values as low as 1.0 and 1.5, with significant decrease in the number of colony forming units. There was a recovery in growth when the yeast was transferred to multiplication medium (sugar cane juice) after the acid treatment. However, the initial number of colonies before the treatment was not reached (Figure 4).


Characteristics of Saccharomyces cerevisiae yeasts exhibiting rough colonies and pseudohyphal morphology with respect to alcoholic fermentation.

Reis VR, Bassi AP, da Silva JC, Ceccato-Antonini SR - Braz. J. Microbiol. (2014)

Growth (cfu/mL) of two yeast strains of S. cerevisiae (52, in black, rough colony; PE-02, in grey, smooth colony), submitted to acid treatment with sulphuric acid at different pH values (1.0, 1.5 and 2.0) at 30 °C for 2 h at 160 rpm. The determination of cfu numbers (in YPD medium) was performed before the acid treatment, immediately after the acid treatment (0 h) and after 18 and 36 h of incubation of the treated cells in multiplication medium (sugar cane juice), at 30 °C and 160 rpm. Different capital and lowercase letters indicate significant differences (p < 0.05) among the treatments for the smooth colony and rough colony, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3958177&req=5

f4-bmj-44-4-1121: Growth (cfu/mL) of two yeast strains of S. cerevisiae (52, in black, rough colony; PE-02, in grey, smooth colony), submitted to acid treatment with sulphuric acid at different pH values (1.0, 1.5 and 2.0) at 30 °C for 2 h at 160 rpm. The determination of cfu numbers (in YPD medium) was performed before the acid treatment, immediately after the acid treatment (0 h) and after 18 and 36 h of incubation of the treated cells in multiplication medium (sugar cane juice), at 30 °C and 160 rpm. Different capital and lowercase letters indicate significant differences (p < 0.05) among the treatments for the smooth colony and rough colony, respectively.
Mentions: For this test, the strains 17 (smooth) and 52 (rough) were chosen to verify the effect of acid treatment on their growth. The first strain (PE-02), is a yeast strain selected for its dominance and persistence throughout the entire harvest season (Basso et al., 2008) and for its high resistance to low pH (Reis 2011); the second strain was chosen because it has a high flocculation rate, as described above, and had resistance to high sugar concentrations and sensitivity to low pH (Reis 2011). The results showed that the rough strain was severely affected by pH values as low as 1.0 and 1.5, with significant decrease in the number of colony forming units. There was a recovery in growth when the yeast was transferred to multiplication medium (sugar cane juice) after the acid treatment. However, the initial number of colonies before the treatment was not reached (Figure 4).

Bottom Line: Among the native yeasts found in alcoholic fermentation, rough colonies associated with pseudohyphal morphology belonging to the species Saccharomyces cerevisiae are very common and undesirable during the process.The effects of acid treatment at different pH values on the growth of two strains ("52"--rough and "PE-02"--smooth) as well as batch fermentation tests with cell recycling and acid treatment of the cells were also evaluated.A fermentative efficiency as low as 60% was observed with the rough colony alone.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Tecnologia Agroindustrial e Socio-Economia Rural, Centro de Ciências Agrárias, Universidade Federal de São Carlos, Via Anhanguera, Araras, SP, Brazil.

ABSTRACT
Among the native yeasts found in alcoholic fermentation, rough colonies associated with pseudohyphal morphology belonging to the species Saccharomyces cerevisiae are very common and undesirable during the process. The aim of this work was to perform morphological and physiological characterisations of S. cerevisiae strains that exhibited rough and smooth colonies in an attempt to identify alternatives that could contribute to the management of rough colony yeasts in alcoholic fermentation. Characterisation tests for invasiveness in Agar medium, killer activity, flocculation and fermentative capacity were performed on 22 strains (11 rough and 11 smooth colonies). The effects of acid treatment at different pH values on the growth of two strains ("52"--rough and "PE-02"--smooth) as well as batch fermentation tests with cell recycling and acid treatment of the cells were also evaluated. Invasiveness in YPD Agar medium occurred at low frequency; ten of eleven rough yeasts exhibited flocculation; none of the strains showed killer activity; and the rough strains presented lower and slower fermentative capacities compared to the smooth strains in a 48-h cycle in a batch system with sugar cane juice. The growth of the rough strain was severely affected by the acid treatment at pH values of 1.0 and 1.5; however, the growth of the smooth strain was not affected. The fermentative efficiency in mixed fermentation (smooth and rough strains in the same cell mass proportion) did not differ from the efficiency obtained with the smooth strain alone, most likely because the acid treatment was conducted at pH 1.5 in a batch cell-recycle test. A fermentative efficiency as low as 60% was observed with the rough colony alone.

Show MeSH
Related in: MedlinePlus