Development of a Novel Microbial Sensor with Baker's Yeast Cells for Monitoring Temperature Control during Cold Food Chain

A novel microbial sensor containing a commercial baker's yeast with a high freeze tolerance was developed for visibly detecting inappropriate temperature control of food. When the yeast cells fermented glucose, the resulting gas production triggered the microbial sensor. The biosensor was a simple, small bag containing a solution of yeast cells, yeast extract, glucose, and glycerol sealed up with multilayer transparent film with barriers against oxygen and humidity. Fine adjustment of gas productivity in the biosensor at low temperatures was achieved by changing either or both concentrations of glucose and yeast cells. Moreover, the amount of time that food was exposed to inappropriate temperatures could be deduced by the amount of gas produced in the biosensor. The biosensor was stable without any functional loss for up to 1 week in frozen storage. The biosensor could offer a useful tool for securing food safety by maintaining low-temperature control in every stage from farm to fork, including during transportation, in the store, and at home.

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Heterologous Expression of Type I Antifreeze Peptide GS-5 in Baker's Yeast Increases Freeze Tolerance and Provides Enhanced Gas Production in Frozen Dough

Journal of Agricultural and Food Chemistry ◽

10.1021/jf0515577 ◽

2005 ◽

Vol 53 (26) ◽

pp. 9966-9970 ◽

Cited By ~ 27

Author(s):

Joaquin Panadero ◽

Francisca Randez-Gil ◽

Jose Antonio Prieto

Keyword(s):

Heterologous Expression ◽

Freeze Tolerance ◽

Gas Production ◽

Baker’S Yeast ◽

Type I ◽

Baker's Yeast ◽

Frozen Dough

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Aquaporin-Mediated Improvement of Freeze Tolerance of Saccharomyces cerevisiae Is Restricted to Rapid Freezing Conditions

Applied and Environmental Microbiology ◽

10.1128/aem.70.6.3377-3382.2004 ◽

2004 ◽

Vol 70 (6) ◽

pp. 3377-3382 ◽

Cited By ~ 35

Author(s):

An Tanghe ◽

Patrick Van Dijck ◽

Didier Colavizza ◽

Johan M. Thevelein

Keyword(s):

Saccharomyces Cerevisiae ◽

Freeze Tolerance ◽

Baker’S Yeast ◽

Yeast Cells ◽

Freezing Injury ◽

Crystal Formation ◽

Rapid Freezing ◽

Baker's Yeast ◽

Cooling Rates ◽

The Difference

ABSTRACT Previous observations that aquaporin overexpression increases the freeze tolerance of baker's yeast (Saccharomyces cerevisiae) without negatively affecting the growth or fermentation characteristics held promise for the development of commercial baker's yeast strains used in frozen dough applications. In this study we found that overexpression of the aquaporin-encoding genes AQY1-1 and AQY2-1 improves the freeze tolerance of industrial strain AT25, but only in small doughs under laboratory conditions and not in large doughs under industrial conditions. We found that the difference in the freezing rate is apparently responsible for the difference in the results. We tested six different cooling rates and found that at high cooling rates aquaporin overexpression significantly improved the survival of yeast cells, while at low cooling rates there was no significant effect. Differences in the cultivation conditions and in the thawing rate did not influence the freeze tolerance under the conditions tested. Survival after freezing is determined mainly by two factors, cellular dehydration and intracellular ice crystal formation, which depend in an inverse manner on the cooling velocity. In accordance with this so-called two-factor hypothesis of freezing injury, we suggest that water permeability is limiting, and therefore that aquaporin function is advantageous, only under rapid freezing conditions. If this hypothesis is correct, then aquaporin overexpression is not expected to affect the leavening capacity of yeast cells in large, industrial frozen doughs, which do not freeze rapidly. Our results imply that aquaporin-overexpressing strains have less potential for use in frozen doughs than originally thought.

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Aquaporin Expression Correlates with Freeze Tolerance in Baker's Yeast, and Overexpression Improves Freeze Tolerance in Industrial Strains

Applied and Environmental Microbiology ◽

10.1128/aem.68.12.5981-5989.2002 ◽

2002 ◽

Vol 68 (12) ◽

pp. 5981-5989 ◽

Cited By ~ 101

Author(s):

An Tanghe ◽

Patrick Van Dijck ◽

Françoise Dumortier ◽

Aloys Teunissen ◽

Stefan Hohmann ◽

...

Keyword(s):

Freeze Tolerance ◽

Baker’S Yeast ◽

Yeast Cells ◽

Northern Analysis ◽

Freezing Process ◽

Crystal Formation ◽

Baker's Yeast ◽

Freeze Resistance ◽

Freeze Thaw ◽

Yeast Strains

ABSTRACT Little information is available about the precise mechanisms and determinants of freeze resistance in baker's yeast, Saccharomyces cerevisiae. Genomewide gene expression analysis and Northern analysis of different freeze-resistant and freeze-sensitive strains have now revealed a correlation between freeze resistance and the aquaporin genes AQY1 and AQY2. Deletion of these genes in a laboratory strain rendered yeast cells more sensitive to freezing, while overexpression of the respective genes, as well as heterologous expression of the human aquaporin gene hAQP1, improved freeze tolerance. These findings support a role for plasma membrane water transport activity in determination of freeze tolerance in yeast. This appears to be the first clear physiological function identified for microbial aquaporins. We suggest that a rapid, osmotically driven efflux of water during the freezing process reduces intracellular ice crystal formation and resulting cell damage. Aquaporin overexpression also improved maintenance of the viability of industrial yeast strains, both in cell suspensions and in small doughs stored frozen or submitted to freeze-thaw cycles. Furthermore, an aquaporin overexpression transformant could be selected based on its improved freeze-thaw resistance without the need for a selectable marker gene. Since aquaporin overexpression does not seem to affect the growth and fermentation characteristics of yeast, these results open new perspectives for the successful development of freeze-resistant baker's yeast strains for use in frozen dough applications.

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Isolation and Characterization of a Freeze-Tolerant Diploid Derivative of an Industrial Baker's Yeast Strain and Its Use in Frozen Doughs

Applied and Environmental Microbiology ◽

10.1128/aem.68.10.4780-4787.2002 ◽

2002 ◽

Vol 68 (10) ◽

pp. 4780-4787 ◽

Cited By ~ 49

Author(s):

Aloys Teunissen ◽

Françoise Dumortier ◽

Marie-Françoise Gorwa ◽

Jürgen Bauer ◽

An Tanghe ◽

...

Keyword(s):

Growth Rate ◽

Frozen Storage ◽

Normal Growth ◽

Freeze Tolerance ◽

Baker’S Yeast ◽

Superior Performance ◽

Baker's Yeast ◽

Laboratory Conditions ◽

Isolation And Characterization ◽

Freeze Tolerant

ABSTRACT The routine production and storage of frozen doughs are still problematic. Although commercial baker's yeast is highly resistant to environmental stress conditions, it rapidly loses stress resistance during dough preparation due to the initiation of fermentation. As a result, the yeast loses gassing power significantly during storage of frozen doughs. We obtained freeze-tolerant mutants of polyploid industrial strains following screening for survival in doughs prepared with UV-mutagenized yeast and subjected to 200 freeze-thaw cycles. Two strains in the S47 background with a normal growth rate and the best freeze tolerance under laboratory conditions were selected for production in a 20-liter pilot fermentor. Before frozen storage, the AT25 mutant produced on the 20-liter pilot scale had a 10% higher gassing power capacity than the S47 strain, while the opposite was observed for cells produced under laboratory conditions. AT25 also retained more freeze tolerance during the initiation of fermentation in liquid cultures and more gassing power during storage of frozen doughs. Other industrially important properties (yield, growth rate, nitrogen assimilation, and phosphorus content) were very similar. AT25 had only half of the DNA content of S47, and its cell size was much smaller. Several diploid segregants of S47 had freeze tolerances similar to that of AT25 but inferior performance for other properties, while an AT25-derived tetraploid, TAT25, showed only slightly improved freeze tolerance compared to S47. When AT25 was cultured in a 20,000-liter fermentor under industrial conditions, it retained its superior performance and thus appears to be promising for use in frozen dough production. Our results also show that a diploid strain can perform at least as well as a tetraploid strain for commercial baker's yeast production and usage.

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Stress Tolerance in Doughs of Saccharomyces cerevisiae Trehalase Mutants Derived from Commercial Baker’s Yeast

Applied and Environmental Microbiology ◽

10.1128/aem.65.7.2841-2846.1999 ◽

1999 ◽

Vol 65 (7) ◽

pp. 2841-2846 ◽

Cited By ~ 70

Author(s):

Jun Shima ◽

Akihiro Hino ◽

Chie Yamada-Iyo ◽

Yasuo Suzuki ◽

Ryouichi Nakajima ◽

...

Keyword(s):

Saccharomyces Cerevisiae ◽

Stress Tolerance ◽

Freeze Tolerance ◽

Fermentation Medium ◽

Baker’S Yeast ◽

Yeast Cells ◽

Baker's Yeast ◽

Critical Determinant ◽

Acid Trehalase ◽

Dry Conditions

ABSTRACT Accumulation of trehalose is widely believed to be a critical determinant in improving the stress tolerance of the yeastSaccharomyces cerevisiae, which is commonly used in commercial bread dough. To retain the accumulation of trehalose in yeast cells, we constructed, for the first time, diploid homozygous neutral trehalase mutants (Δnth1), acid trehalase mutants (Δath1), and double mutants (Δnth1 ath1) by using commercial baker’s yeast strains as the parent strains and the gene disruption method. During fermentation in a liquid fermentation medium, degradation of intracellular trehalose was inhibited with all of the trehalase mutants. The gassing power of frozen doughs made with these mutants was greater than the gassing power of doughs made with the parent strains. The Δnth1 and Δath1strains also exhibited higher levels of tolerance of dry conditions than the parent strains exhibited; however, the Δnth1 ath1 strain exhibited lower tolerance of dry conditions than the parent strain exhibited. The improved freeze tolerance exhibited by all of the trehalase mutants may make these strains useful in frozen dough.

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