Yeast Is A Miraculous Organism To Be Thankful For

November 6, 2022 at 8:22 p.m.


If there is a better sandwich than a bocadillo I haven’t found it.  

The bocadillo (small mouthful in Spanish) is popular in Spain and consists of freshly baked sourdough bread, Manchego cheese, Serrano ham, peppers and  Dijon mustard. I love the sandwich with a cold beer, preferentially Spanish or Mexican.

The key ingredients of this meal, the cheese, bread and beer owe their existence to a variety of domesticated yeasts.  Without them none of these delicious foods would exist.

Description

A single yeast cell is about five to 10 microns in size and round to ovoid in shape. A yeast cell is 10 times larger than bacteria but still too small to be seen by the naked eye. In fact, it takes more than 10 yeast cells to equal the diameter of one human hair. A small, visible yeast colony on a Petri dish contains at least 1 million cells. There are more than 500 species of yeast, and within each species are thousands of different yeast strains.

Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitute 1% of all described fungal species.  Yeasts reproduce  asexually by budding or fission and sexually by spore formation.  Most yeast species belong to Ascomycotina, a few are basidiomycetes. Bakers' yeast and the yeasts used in brewing, winemaking, and distilling are strains of Saccharomyces cerevisiae, belonging to the family Saccharomycetaceae in Ascomycotina.

History

In 1680, Anton van Leeuwenhoek was first to observe, through a microscope, that yeast was composed of small, interconnected elements. Interestingly, he did not realize that it was alive. At that time, the most commonly accepted theory of fermentation was that it was a spontaneous process — a chemical reaction promoted by contact with the air — and the yeast was a chemical by-product.  

Another century later, in 1789, Antoine-Laurent Lavoisier described the chemical nature of fermentation as parts of sugar turning into carbon dioxide and alcohol. Yet scientists still did not make the connection between yeast and this conversion of sugar into ethanol.

It was not until the mid-1800s that Louis Pasteur established that yeast was a living microorganism. This opened the gates for precisely controlling the conversion of sugar into alcohol. It also led to the creation of a separate field of study called biochemistry. The advances made, as direct or indirect results of beer research, led to our understanding of how cells work and laid the groundwork for many other breakthroughs in scientific research. When Pasteur started working with beer fermentation in the 1860s, most people believed yeast was not the causative agent of fermentation.

Beer is a complex soup of material, containing protein, nucleic acids, bacteria, yeast and much more. Scientists knew yeast was part of the mix, but they regarded it as a by-product of the fermentation. They believed spontaneous generation catalyzed by air caused fermentation.

Fermentation

 Fermentation is defined as the chemical breakdown of a substance by bacteria, yeasts, or other microorganisms, typically involving effervescence and the giving off of heat. The process is involved in the making of beer, wine and liquor in which sugars are converted to ethyl alcohol. For most of history it was a divine mystery.  

The most important part of fermentation is the yeast.  By converting sugar to other compounds the taste of fermented foods and beverages is influenced. Yeast do this in order to make energy and gain material for reproduction. The yeast does not care that you are trying to make great beer or affect the taste of bread or cheese.  Yeasts contain a unique set of metabolic genes which allow them to break down distinct types of sugar metabolites.

Yeast Strains

The yeast strains used are critically important to everything related to fermentation. Like people, each strain has a distinct personality. In fact, successive generations of the same yeast family will have their own unique attributes, whether related to fermentation temperature, oxygen requirements or level of attenuation. In the end, perhaps the most important factor in good fermentation is preventing contamination from competing with the yeast.

Final Thoughts

In addition to being widely exploited in the production of foods, beverages, and pharmaceuticals, yeasts play significant roles as model eukaryotic cells in furthering our knowledge in the biological and biomedical sciences. Several yeasts have had their genomes completely sequenced and research is under way to assign a physiological function to sequenced yeast genes. The study of yeasts not only provides insights into how a simple eukaryote works but also leads to understanding of several human diseases and heritable disorders. An excellent book about yeasts and beer fermentation is entitled “Yeast” and written by Chris White and Jamil Zainasheff.

Max Sherman is a medical writer and pharmacist retired from the medical device industry.  His new book “Science Snippets” is available from Amazon and other book sellers. It contains a number of previously published columns.  He can be reached by email at  [email protected].  



If there is a better sandwich than a bocadillo I haven’t found it.  

The bocadillo (small mouthful in Spanish) is popular in Spain and consists of freshly baked sourdough bread, Manchego cheese, Serrano ham, peppers and  Dijon mustard. I love the sandwich with a cold beer, preferentially Spanish or Mexican.

The key ingredients of this meal, the cheese, bread and beer owe their existence to a variety of domesticated yeasts.  Without them none of these delicious foods would exist.

Description

A single yeast cell is about five to 10 microns in size and round to ovoid in shape. A yeast cell is 10 times larger than bacteria but still too small to be seen by the naked eye. In fact, it takes more than 10 yeast cells to equal the diameter of one human hair. A small, visible yeast colony on a Petri dish contains at least 1 million cells. There are more than 500 species of yeast, and within each species are thousands of different yeast strains.

Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitute 1% of all described fungal species.  Yeasts reproduce  asexually by budding or fission and sexually by spore formation.  Most yeast species belong to Ascomycotina, a few are basidiomycetes. Bakers' yeast and the yeasts used in brewing, winemaking, and distilling are strains of Saccharomyces cerevisiae, belonging to the family Saccharomycetaceae in Ascomycotina.

History

In 1680, Anton van Leeuwenhoek was first to observe, through a microscope, that yeast was composed of small, interconnected elements. Interestingly, he did not realize that it was alive. At that time, the most commonly accepted theory of fermentation was that it was a spontaneous process — a chemical reaction promoted by contact with the air — and the yeast was a chemical by-product.  

Another century later, in 1789, Antoine-Laurent Lavoisier described the chemical nature of fermentation as parts of sugar turning into carbon dioxide and alcohol. Yet scientists still did not make the connection between yeast and this conversion of sugar into ethanol.

It was not until the mid-1800s that Louis Pasteur established that yeast was a living microorganism. This opened the gates for precisely controlling the conversion of sugar into alcohol. It also led to the creation of a separate field of study called biochemistry. The advances made, as direct or indirect results of beer research, led to our understanding of how cells work and laid the groundwork for many other breakthroughs in scientific research. When Pasteur started working with beer fermentation in the 1860s, most people believed yeast was not the causative agent of fermentation.

Beer is a complex soup of material, containing protein, nucleic acids, bacteria, yeast and much more. Scientists knew yeast was part of the mix, but they regarded it as a by-product of the fermentation. They believed spontaneous generation catalyzed by air caused fermentation.

Fermentation

 Fermentation is defined as the chemical breakdown of a substance by bacteria, yeasts, or other microorganisms, typically involving effervescence and the giving off of heat. The process is involved in the making of beer, wine and liquor in which sugars are converted to ethyl alcohol. For most of history it was a divine mystery.  

The most important part of fermentation is the yeast.  By converting sugar to other compounds the taste of fermented foods and beverages is influenced. Yeast do this in order to make energy and gain material for reproduction. The yeast does not care that you are trying to make great beer or affect the taste of bread or cheese.  Yeasts contain a unique set of metabolic genes which allow them to break down distinct types of sugar metabolites.

Yeast Strains

The yeast strains used are critically important to everything related to fermentation. Like people, each strain has a distinct personality. In fact, successive generations of the same yeast family will have their own unique attributes, whether related to fermentation temperature, oxygen requirements or level of attenuation. In the end, perhaps the most important factor in good fermentation is preventing contamination from competing with the yeast.

Final Thoughts

In addition to being widely exploited in the production of foods, beverages, and pharmaceuticals, yeasts play significant roles as model eukaryotic cells in furthering our knowledge in the biological and biomedical sciences. Several yeasts have had their genomes completely sequenced and research is under way to assign a physiological function to sequenced yeast genes. The study of yeasts not only provides insights into how a simple eukaryote works but also leads to understanding of several human diseases and heritable disorders. An excellent book about yeasts and beer fermentation is entitled “Yeast” and written by Chris White and Jamil Zainasheff.

Max Sherman is a medical writer and pharmacist retired from the medical device industry.  His new book “Science Snippets” is available from Amazon and other book sellers. It contains a number of previously published columns.  He can be reached by email at  [email protected].  



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