Historic Beer Birthday: Antonie van Leeuwenhoek

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Today is the birthday of Antonie van Leeuwenhoek (October 24, 1632–August 26, 1723). He “was a Dutch tradesman and scientist, and is commonly known as ‘the Father of Microbiology.'” Apropos of nothing, “his mother, Margaretha (Bel van den Berch), came from a well-to-do brewer’s family.” Despite hi family ties, van Leeuwenhoek didn’t discover anything specifically useful to the brewing industry, but he did find that there was life pretty much everywhere he looked, using his microscope, including the “microscope—tiny “animalcules,” including yeast cells, which he described for the first time” in 1674-80.” But he laid the groundwork for later scientists to figure how exactly yeast worked. As Brian Hunt wrote in the entry for “infection” in the “The Oxford Companion to Beer,” that “the existence of yeast as a microbe was only discovered in 1674 by Antonie van Leeuwenhoek, the inventor of the modern microscope.” Or as Sylvie Van Zandycke, PhD, put it. “The yeast Saccharomyces cerevisiae was used for thousands of years in the fermentation of alcoholic beverages before anyone realized it! The Dutch scientist, Anton Van Leeuwenhoek observed the mighty cells for the first time under the microscope in 1680.”

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Here’s a short biography, from the Science Museum Brought to Life:

Leeuwenhoek was born in Delft in the Netherlands, to a family of brewers. He is known for his highly accurate observations using microscopes.

Leeuwenhoek worked as a draper, or fabric merchant. In his work he used magnifying glasses to look at the quality of fabric. After reading natural scientist Robert Hooke’s highly popular study of the microscopic world, called Micrographia (1665), he decided to use magnifying lenses to examine the natural world. Leeuwenhoek began to make lenses and made observations with the microscopes he produced. In total he made over 500 such microscopes, some of which allowed him to see objects magnified up to 200 times.

These were not the first microscopes, but Leeuwenhoek became famous for his ability to observe and reproduce what was seen under the microscope. He hired an illustrator who reproduced the things Leeuwenhoek saw.

In 1673 he began corresponding with the Royal Society of London, which had just formed. Leeuwenhoek made some of the first observations of blood cells, many microscopic animals, and living bacteria, which he described as ‘many very little living animalcules’. In 1680 his work was recognised with membership of the Royal Society – although he never attended a meeting, remaining all his life in Delft.

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Leeuwenhoek with His Microscope, by Ernest Board (1877–1934)

Here’s a story from Gizmodo, by Esther Inglis-Arkell, explaining Antonie van Leeuwenhoek’s role and iviting readers to Meet The First Man To Put Beer Under A Microscope:

The man in the picture [the same one at the top of this post] is considered the “Father of Microbiology.” He helped to discover and sketch microorganisms. When he turned his microscope on beer, he saw some of the most useful microorganisms in the world — but he failed to recognize them.

This man above is Anton van Leeuwenhoek, and he’s wearing an absolutely bitchin’ coat because he was a draper by trade. In fact, he draped so successfully that he managed to indulge his hobbies as he got older, one of which was lens making. Anton spent his days making powerful microscopes and sketching the objects he put in front of them. He discovered many things, the most interesting of which were animalcules, things that looked like tiny little animals. His sketches and descriptions, as well as his microscopes, jumpstarted the field of microbiology.

It wasn’t long before he turned his lens on beer in the process of brewing. It was 1680 when he first trained his lens on a droplet of beer. At the time, no one knew what it was that made hops, barley, and water turn into beer. Although they knew of yeast as a cloudy substance that appeared in beer after it spent some time fermenting, they were entirely ignorant of what it did; to the point where there were laws against using anything except barley, hops, and water in the beer-making process. Naturally, as soon as Anton looked at brewing beer he saw little circular blobs. He saw the way they aggregated into larger groups. He saw the way that they produced bubbles of what he thought was “air,” and floated to the surface.

Leeuwenhoek-globs

Despite his obsession with microorganisms, he utterly failed to recognize them as life. These blobs, he believed, had come loose from flour. They aggregated into groups of six as part of a chemical process. Anton was fascinated by these groups of flour globs. He modeled them in wax, because he wanted to figure out the ways six globs could stick together while all being visible from above. This is his sketch of his models.

It took another 150 years before Charles Canard-Latour figured out that the “air” was carbon dioxide and the sextets of blobs hadn’t aggregated together, they’d grown. Archaeologists believe that beer was probably first brewed around 3000 BC. That means that we used an organism for nearly 5,000 years before we realized it even existed.

Although van Leeuwenhoek did write about the wood used in beer barrels:

Leeuwenhoek-wood

Beer, Diapers and Correlation

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This is only marginally about beer, but since I’m often reading over data, statistics and scientific reports, notions of causation and correlation have become a subject of great interest. This is a Slideshare by Mark Madson, a research analyst with Third Nature in Portland, Oregon. Apparently in schools teaching business, marketing and the like, instructors often include a tale showing a correlation between the sales of beer and diapers, to illustrate thinking in new ways and how seemingly unrelated items might be connected, or could be connected by a savvy company. Having worked retail for many years during various stages of my life, the science of getting a customer’s attention through shelf placement, cross-merchandising and other strategies I find fascinating, in part because it’s a window into human nature itself. In his presentation, Beer, Diapers, and Correlation: A Tale of Ambiguity, Madson examines the oft-related story of a correlation between beer and diapers and tries to find out its origin and whether or not it’s actually true.

The story of the correlation between beer and diaper sales is commonly used to explain product affinities in introductory data mining courses. Rarely does anyone ask about the origin of this story. Is it true? Why is it true? What does true mean anyway?

The latter question is the most interesting because it challenges the ideas of accuracy in data and analytic models.

This is the real history of the beer and diapers story, explaining its origins and truth, based on repeated analyses of retail data over two decades. It will show that one can have multiple contradictory results from analytic models, and how they can all be true.

As Thirsty As A Fish

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Here’s an interesting bit of history from the 1860s. As far as I can tell, it was published in The Illustrated Times on October 10, 1863. It was drawn by Charles H. Bennett, a well-known Victorian cartoon artist, who worked for many publications, as well as providing art illustrating several books, as well. This was titled “As thirsty as a fish,” and was a satire on Darwin’s “Origin of Species,” which had just been published in 1859. Here’s how it was described. “Showing the evolution of a fish to a beer drinker, with his fin in his pocket, a few old rags, a convenient leaning post and committed to a constant thirst that no amount of beer can quench.”

And in the book, “Charles Darwin and Victorian Visual Culture,” by Jonathan Smith when “As Thirsty As A Fish” appeared in book form, it was accompanied by text indicating it “depicts the British workman as a drunkard who sees business, duty, and friendship merely as impediments to his indulgence.”

Apparently the “Origin of the Species” satires, known as “Development Drawings,” were pretty popular, as there were at least eighteen of them I turned up in a search of Yooniq Images. “As Thirsty As A Fish” appears to have been numbered “No. 20″ in the book, so it seems likely there were even more.

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Patent No. 3607298A: Hop Concentrates

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Today in 1971, US Patent 3607298 A was issued, an invention of Robert O. V. Lloyd and William Mitchell Hatfield, assigned to Bush Boake Allen Ltd., for his “Hop Concentrates.” There’s no Abstract, although in the description it includes these claims:

The present invention relates to hop extracts, including isomerized hop extracts and to processes for their production.

Hops contain, among other things: soft and hard resins including such weakly acidic compounds as humulones (e.g. humulone, cohumulone and adhumulone) and lupulones; essential oils which are those relatively volatile oils which contribute to the characteristic odor of hops; fixed oils, which are contained in the hop seeds and are not readily distilled or extracted by hot water; and water-soluble material such as tannins and proteins.

In the traditional brewing process hops are boiled with wort, which is an aqueous solution of malt sugars. As a consequence of the boiling, a variety of resins and oils pass into the wort. Of these the most important are the humulones, which on boiling are partially isomerized to form water-soluble isohumulones. It is believed that the isohumulones are the principle bittering agent present in the finished beer, but a very large number of other compounds of widely differing chemical nature are also present in traditional beer and contribute to its properties. in the traditional process only a small proportion of the humulones present in the hops are isomerized and taken into solution. Further disadvantages of the traditional method are the need to store a large bulk of hops, which are liable to deteriorate, and the variability of flavor between batches.

The extraction of hops by solvents to give hop extracts which can be used to replace or augment hops in the brewing of beers and ales has received considerable attention for many years. This problem has attracted increased attention during the last l years because of the development in the chemistry of hop constituents and because the brewing industry has become rather less conservative in its attitude toward changes in materials and methods.

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Patent No. 1391561A: Food Product Obtained From Brewers’ Yeast

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Today in 1918, US Patent 1391561 A was issued, an invention of John C. Miller, for his “Food Product Obtained From Brewers’ Yeast.” There’s no Abstract, although in the description it includes these claims:

Brewers waste yeast when dried has for some years been utilized for a force feed for animals. When analyzed, the dried brewers yeast contains, on an average, about fifty-four per cent crude protein, twenty-five per cent nitrogen free extract, two per cent crude fat and ten per cent ash and fiber.

I have discovered that when properly prepared, a flour can be obtained from the brewers waste yeast which can be effectively and properly used when mixed with wheat flour, or when used by itself, as a food product for human consumption.

In the processes heretofore employed in drying brewers yeast, the material has been dried on steam heated rollers and scraped therefrom from by scraping knives, which renders the material coarse and gritty. The older dried products have never been suitable for either as a substitute for or when mixed with wheat flour for human consumption.

In preparing my product, the wet material in the preferred apparatus is delivered into the rapidly rotation cylinder from which it is discharged by centrifugal force at the delivery end of the cylinder in the form of a very fine annular spray and is there subjected to a current of heated air, which is blown annularly across the centrifugally discharged material, so that the moisture is very rapidly taken up and the material can be readily collected in the form of a dry powder free from grit and in the condition of a flour.

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Historic Beer Birthday: John Ewald Siebel

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Today is the birthday of John Ewald Siebel (September 17, 1868-December 20, 1919). Siebel was born in Germany, but relocated to Chicago, Illinois as a young man. Trained as a chemist, in 1868 he founded the Zymotechnic Institute, which was later renamed the Siebel Institute of Technology.

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Here’s his obituary from the Foreign Language Press Survey:

Professor John Ewald Siebel has died after an active life devoted to science. Besides his relatives, thousands of his admirers, including many men of science, mourn at the bier of the friendly old man. He died in his home at 960 Montana Avenue.

Professor Siebel was born September 18, 1845, in Hofkamp, administrative district of Dusseldorf [Germany], as the son of Peter and Lisette Siebel; he attended high school [Real-Gymnasium] at Hagen and studied chemistry at the Berlin University. He came to the United States in 1865 and shortly afterwards obtained employment as a chemist with the Belcher Sugar Refining Company in Chicago. Already in 1868, he established a laboratory of his own, and from 1869 until 1873 he was employed as official chemist for the city and county. In 1871 he also taught chemistry and physics at the German High School. From 1873 until 1880 he was official gas inspector and city chemist. During the following six years he edited the American Chemical Review, and from 1890 until 1900 he published the Original Communications of Zymotechnic Institute. He was also in charge of the Zymotechnic Institute, which he had founded in 1901. Until two years ago he belonged to its board of directors.

Among the many scientific works published by the deceased, which frequently won international reputation, and are highly valued by the entire world of chemical science are: Newton’s Axiom Developed; Preparation of Dialized Iron; New Methods of Manufacture of Soda; New Methods of Manufacture of Phosphates; Compendium of Mechanical Refrigeration; Thermo-and Electro-Dynamics of Energy Conversion; etc. The distilling industry considered him an expert of foremost achievement.

The deceased was a member of the Lincoln Club; the old Germania Club; the local Academy of Science; the Brauer and Braumeisterverein [Brewer and Brewmaster Association]; the American Institute for Brewing; and the American Society of Brewing Technology. Professor Siebel was also well known in German circles outside the city and state.

His wife Regina, whom he married in 1870….died before him. Five sons mourn his death: Gustav, Friedrich, Ewald, Emil and Dr. John Ewald Siebel, Jr. Funeral services will be held tomorrow afternoon at Graceland Cemetery.

Professor Siebel was truly a martyr of science. He overworked himself, until a year ago he suffered a nervous breakdown. About four months ago conditions became worse. His was an easy and gentle death.

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The Siebel Institute’s webpage tells their early history:

Dr. John Ewald Siebel founded the Zymotechnic Institute in 1868. He was born on September 17, 1845, near Wermelskirchen in the district of Dusseldorf, Germany. He studied physics and chemistry and earned his doctorate at the University of Berlin before moving to Chicago 1866. In 1868 he opened John E. Siebel’s Chemical Laboratory which soon developed into a research station and school for the brewing sciences.

In 1872, as the company moved into new facilities on Belden Avenue on the north side of Chicago, the name was changed to the Siebel Institute of Technology. During the next two decades, Dr. Siebel conducted extensive brewing research and wrote most of his over 200 books and scientific articles. He was also the editor of a number of technical publications including the scientific section of The Western Brewer, 100 Years of Brewing and Ice and Refrigeration.

In 1882 he started a scientific school for brewers with another progressive brewer but the partnership was short lived. Dr. Siebel did, however, continue brewing instruction at his laboratory. The business expanded in the 1890’s when two of Dr. Siebel’s sons joined the company.

The company was incorporated in 1901 and conducted brewing courses in both English and German. By 1907 there were five regular courses: a six-month Brewers’ Course, a two-month Post Graduate Course, a three-month Engineers’ Course, a two-month Maltsters’ Course and a two-month Bottlers’ Course. In 1910, the school’s name, Siebel Institute of Technology, was formally adopted. With the approach of prohibition, the Institute diversified and added courses in baking, refrigeration, engineering, milling, carbonated beverages and other related topics. On December 20, 1919, just twenty-seven days before prohibition became effective, Dr. J. E. Siebel passed away.

With the repeal of prohibition in 1933 the focus of the Institute returned to brewing under the leadership of F. P. Siebel Sr., the eldest son of Dr. J. E. Siebel. His sons, Fred and Ray, soon joined the business and worked to expand its scope. The Diploma Course in Brewing Technology was offered and all other non-brewing courses were soon eliminated. Then in October 1952, the Institute moved to its brand new, custom built facilities on Peterson Avenue where we have remained for almost 50 years.

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Siebel Brewers Academy c. 1902-04.

Here’s another short account from the journal Brewery History, in an article entitled “A History of Brewing Science in the United States of America,” by Charles W. Bamforth:

Dr John Ewald Siebel (1845-1919) was born on September 17th 1845 at Hofcamp, near Düsseldorf. Upon visiting an uncle in US after the completion of his doctorate in chemistry and physics he became chief chemist at Belcher’s sugar refinery in Chicago, aged 21, but that company soon folded. Siebel stayed in Chicago to start an analytical laboratory in 1868, which metamorphosed into the Zymotechnic Institute.

With Chicago brewer Michael Brand, Siebel started in 1882 the first Scientific School for practical brewers as a division of the Zymotechnic Institute. True life was not breathed into the initiative until 1901 with Siebel’s son (one of five) Fred P. Siebel as manager. This evolved to become the Siebel Institute of Technology, which was incorporated in 1901 and conducted brewing courses in both English and German. Within 6 years five regular courses had been developed: a six-month course for brewers, a twomonth post graduate course, a threemonth course for engineers, a two-month malting course and a two-month bottling course.

Amongst Siebel’s principal contributions were work on a counter pressure racker and artificial refrigeration systems. Altogether he published more than 200 articles on brewing, notably in the Western Brewer and original Communications of the Zymotechnic Institute. Brewing wasn’t his sole focus, for instance he did significant work on blood chemistry.

Son EA Siebel founded Siebel and Co and the Bureau of Bio-technology in 1917, the year that prohibition arrived. Emil Siebel focused then on a ‘temperance beer’ that he had been working on for nine years. Courses in baking, refrigeration, engineering, milling and nonalcoholic carbonated beverages were offered.

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And here’s the entry for the Siebel Institute from the Oxford Companion to Beer, written by Randy Mosher:

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Patent No. 3526510A: Beer Foam Adhesion

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Today in 1970, US Patent 3526510 A was issued, an invention of John B. Bockelmann, Leonard Raymond and William Tirado, assigned to the F. & M. Schaefer Brewing Co. for their “Beer Foam Adhesion.” There’s no Abstract, although in the description it includes these claims:

The present invention relates to a novel method of enhancing so-called foam cling in certain beers or the like, as hereinafter more specifically set forth.

The use, as additive, of the heptyl ester or the octyl ester of para-hydroxy-benzoic acid, as such or in the form of an alkali metal salt or alkaline earth metal salt thereof, as a chemical pasteurizer for-“beer (cf. US. Pat. No. 3,232,766) has eliminated the necessity for conventional pasteurization as a means for preserving beer against undesired bacterial growth. However, the presence of the said additive in beer is bound up with a drawback in that the normal foam produced by the pouring of the beer into a glass no longer has the adhesion or cling which is generally associated with beer quality and which is produced by conventional pasteurized or draft beer.

Various agents are known for achieving good adhesion to the sides of the glass from beer containing the aforesaid additives. However, these are bound up with one disadvantage or another. Elimination of the additive agents results in a beer foam that rapidly wipes the glass clean, leaving no beer foam cling and imparting, from the standpoint of those who equate beer foam cling with good quality and good appearance, an inis a desideratum in the art of making paraban-pasteurized finished beer to provide an additive which is free from any disadvantage or undesired drawback and which imparts to the beer containing heptyl or octyl ester of para-hydroxy benzoic acid the capacity of forming, upon being poured into a glass, a normal foam of good stability and good cling (sometimes referred to as curtain formation).

A primary object of the present invention is the realization of the aforesaid desideratum. Briefly stated, this is achieved according to the present invention by the expedient of incorporating into beer which has been paraben-pasteurized an appropriate and effective amount of, as foam stabilizer and curtain former, one or more of .(a) sodium dioctyl sulfosuccinate (cf. US. Pat. No. 2,441,341); (b) sodium dihexyl sulfosuccinate;- (c) sodium diamyl sulfosuccinate; (d) disodium N-octadecyl sulfosuccinamate (cf. US. Pat. No. 2,252,401); and (e) tetrasodium N-(1,2-dicarboxyethyl)-N-octadecylsulfosuccinamate (cf. US. Pat. No. 2,438,092).

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Patent No. 3977953A: Process For The Production Of Hulupones

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Today in 1897, US Patent 3977953 A was issued, an invention of Hubert Frhr. Von Hirsch and Alfons Hartl, assigned to the Atlantic Research Institute, for their “Process For the Production of Hulupones.” Here’s the Abstract:

Lupulones, which form a constituent of hop resins which have hitherto been separated and discarded because of their poor solubility, are converted into a hulupone-containing beer-soluble bitter-tasting product by photo-sensitized oxidation in a liquid alkaline medium. However, the oxidation, which is effected by means of oxygen or an oxygen-containing gas in the presence of one or more sensitizing dyes and under the action of visible light, is only partial; it is discontinued when the oxygen consumption resulting from the reaction exhibits a substantial decline, or when the fall in pH occurring during the reaction substantially ceases.

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Historic Beer Birthday: Hans Adolf Krebs

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Today is the birthday of Hans Adolf Krebs (August 25, 1900-November 22, 1981). He was a German-born British physician and biochemist. He was the pioneer scientist in study of cellular respiration, a biochemical pathway in cells for production of energy. He is best known for his discoveries of two important chemical reactions in the body, namely the urea cycle and the citric acid cycle. The latter, the key sequence of metabolic reactions that produces energy in cells, often eponymously known as the “Krebs cycle,” earned him a Nobel Prize in Physiology or Medicine in 1953. And it’s the Krebs cycle that is his relation to brewing, as it’s also known as the respiratory phase, the second aerobic state of the fermentation process immediately following the lag period.

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Here’s a description of the Krebs cycle from Life Fermented:

The Krebs cycle, also known as the tricarboxylic acid (TCA) cycle or the citric acid cycle, is a circular and repeating set of reactions which requires oxygen. In beer making, this would occur in the first stage of fermentation when the yeast is pitched into a well aerated wort, and carries on until all oxygen is used up.
Pyruvate (are you tired of this word yet?) is first converted to acetyl-CoA (pronounced “Co-A”) in the following reaction:

pyruvate + 2 NAD+ + CoA-SH → acetyl-CoA + CO2 + NADH, with the help of the pyruvate dehydrogenase (PDH) complex. Note that this is the first time CO2 is produced, and yet more NADH is generated.

This acetyl-CoA then enters into a cycle of reactions which nets two molecules of CO2, one GTP (guanosine triphosphate, another unit of energy equivalent to ATP), three NADH, and one FADH2 (flavin adenine dinucleotide, which functions similarly to NADH). After the cycle completes, another acetyl-CoA molecule enters and the cycle repeats itself.

But wait, this just made more NADH, and we need to regenerate NAD+ so glycolysis can continue. Both the NADH and FADH2 now donate their electrons to a process called the electron transport chain/ oxidative phosphorylation. The result is a return of NAD to the NAD+ state, and a large amount of ATP cellular energy.

Because the Krebs cycle is so efficient at producing ATP energy units, this is the yeast’s preferred pathway. But, you’ll notice a rather conspicuous absence: ethanol. This is only formed in the absence of oxygen.

NPG x88332; Sir Hans Adolf Krebs

Here’s a biography of Krebs, from the Nobel Prize website:

Sir Hans Adolf Krebs was born at Hildesheim, Germany, on August 25th, 1900. He is the son of Georg Krebs, M.D., an ear, nose, and throat surgeon of that city, and his wife Alma, née Davidson.

Krebs was educated at the Gymnasium Andreanum at Hildesheim and between the years 1918 and 1923 he studied medicine at the Universities of Göttingen, Freiburg-im-Breisgau, and Berlin. After one year at the Third Medical Clinic of the University of Berlin he took, in 1925, his M.D. degree at the University of Hamburg and then spent one year studying chemistry at Berlin. In 1926 he was appointed Assistant to Professor Otto Warburg at the Kaiser Wilhelm Institute for Biology at Berlin-Dahlem, where he remained until 1930.

In I930, he returned to hospital work, first at the Municipal Hospital at Altona under Professor L. Lichtwitz and later at the Medical Clinic of the University of Freiburg-im-Breisgau under Professor S. J. Thannhauser.

In June 1933, the National Socialist Government terminated his appointment and he went, at the invitation of Sir Frederick Gowland Hopkins, to the School of Biochemistry, Cambridge, where he held a Rockefeller Studentship until 1934, when he was appointed Demonstrator of Biochemistry in the University of Cambridge.

In 1935, he was appointed Lecturer in Pharmacology at the University of Sheffield, and in 1938 Lecturer-in-Charge of the Department of Biochemistry then newly founded there.

In 1945 this appointment was raised to that of Professor, and of Director of a Medical Research Council’s research unit established in his Department. In 1954 he was appointed Whitley Professor of Biochemistry in the University of Oxford and the Medical Research Council’s Unit for Research in Cell Metabolism was transferred to Oxford.

Professor Krebs’ researches have been mainly concerned with various aspects of intermediary metabolism. Among the subjects he has studied are the synthesis of urea in the mammalian liver, the synthesis of uric acid and purine bases in birds, the intermediary stages of the oxidation of foodstuffs, the mechanism of the active transport of electrolytes and the relations between cell respiration and the generation of adenosine polyphosphates.

Among his many publications is the remarkable survey of energy transformations in living matter, published in 1957, in collaboration with H. L. Kornberg, which discusses the complex chemical processes which provide living organisms with high-energy phosphate by way of what is known as the Krebs or citric acid cycle.

Krebs was elected a Fellow of the Royal Society of London in 1947. In 1954 the Royal Medal of the Royal Society, and in 1958 the Gold Medal of the Netherlands Society for Physics, Medical Science and Surgery were conferred upon him. He was knighted in 1958. He holds honorary degrees of the Universities of Chicago, Freiburg-im-Breisgau, Paris, Glasgow, London, Sheffield, Leicester, Berlin (Humboldt University), and Jerusalem.

He married Margaret Cicely Fieldhouse, of Wickersley, Yorkshire, in 1938. They have two sons, Paul and John, and one daughter, Helen.

And in the Microbe Wiki, on a page entitled “Saccharomyces cerevisiae use and function in alcohol production,” under a section called “Fermentation of alchohol,” the Krebs cycle is placed in its portion in the fermentation process:

Saccharomyces cerevisiae is able to perform both aerobic and anaerobic respiration. The process begins with the yeast breaking down the different forms of sugar in the wort. The types of sugars typically found in wort are the monosaccharides glucose and fructose. These sugars contain a single hexose, which is composed of 6 carbon atoms in the molecular formula C6H12O6. Disaccharides are formed when two monosaccharides join together. Typical disaccharides in the wort are galactose, sucrose, and maltose. The third type of fermentable sugar in the wort is a trisaccharide. This trisaccharide is formed when three monosccharides join together. Maltotriose is the trisaccharide commonly found in the wort and is composed of three glucose molecules. The wort does contain other sugars such as dextrins but it is not fermentable by yeast10. These dextrins contain four monosaccarides joined together. In order for the yeast to use the disaccharides and trisaccharides they first must be broken down to monosaccharides. The yeast does this by using different enzymes both inside and outside the cell. The enzyme invertase is used to break down sucrose into glucose and fructose. The invertase catalyzes the hydrolysis of the sucrose by breaking the O-C (fructose bond). The other enzyme used is maltase, which breaks down maltose and maltotriose into glucose inside the cell. The enzyme does this by catalyzing the hydrolysis of the sugars by breaking the glycosidic bond holding the glucose molecules together.

Once the sugars are broken down into monosaccharides the yeast can use them. The primary step is called glycolysis. In this process the glucose is converted to pyruvate using different enzymes in a series of chemical modifications. The electrons from glucose end up being transferred to energy carrying molecules like NAD+ to form NADH. ATP is also formed when phosphates are transferred from high-energy intermediates of glycolysis to ADP. In the presence of oxygen aerobic respiration can occur. This occurs in the mitochondria of the yeast. The energy of the pyruvate is extracted when it goes through metabolic processes like the Krebs cycle. The products of this type of metabolism are ATP, H2O, and CO2. However if there is no oxygen present and an abundance of sugars, as in the wort, the yeast undergo alcoholic fermentation. This type of metabolism yields much smaller amounts of energy when compared to aerobic respiration. However, because of the large supply of sugars from the different grains the wort is a very good environment for fermentative growth. The alcoholic fermentation begins with the two pyruvate acquired from glycolysis. These two pyruvate are decarboxylated by pyruvate decarboxylase to form two acetaldehydes and CO2. The CO2 is the gas that is observed during fermentation as bubbles that float to the top of the wort creating the kräusen or beer head, the foam that is very characteristic of a freshly poured beer. Pyruvate decarboxylase is a homotetramer meaning it contains four identical subunits. This also means that is has four active sites. The active sites are where the pyruvate reacts with the cofactors thiamine pyrophosphate (TPP) and magnesium to remove the carbon dioxide9. The final step to form alcohol is the addition of a hydrogen ion to the aldehyde to form ethanol. This hydrogen ion is from the NADH made during glycolysis and converts back to NAD+. The ethanol is originally believed to serve as an antibiotic against other microbes. This form of defense ensures that bacteria do not grow in the wort, thus ruining the beer with off flavors. However recently with the boom of craft beer different bacteria have been purposefully added to create what is known as sour beer. The sour taste comes from the waste products of the bacteria.

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To learn more about the Krebs cycle check out this video from the University of Oklahoma’s Chemistry of Beer – Unit 7 – Chemical Concepts: Krebs Cycle:

Historic Beer Birthday: Johan Kjeldahl

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Today is the birthday of Johan Gustav Christoffer Thorsager Kjeldahl (August 16, 1849-July 18, 1900) He was a Danish chemist who developed a method for determining the amount of nitrogen in certain organic compounds using a laboratory technique which was named the Kjeldahl method after him.

Johan-Kjeldahl

Kjeldahl worked in Copenhagen at the Carlsberg Laboratory, associated with Carlsberg Brewery, where he was head of the Chemistry department from 1876 to 1900.

He was given the job to determine the amount of protein in the grain used in the malt industry. Less protein meant more beer. Kjeldahl found the answer was in developing a technique to determine nitrogen with accuracy but existing methods in analytical chemistry related to proteins and biochemistry at the time were far from accurate.

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A painting by Otto Haslund of Johan Kjeldahl.

His discovery became known as the Kjeldahl Method

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The method consists of heating a substance with sulphuric acid, which decomposes the organic substance by oxidation to liberate the reduced nitrogen as ammonium sulphate. In this step potassium sulphate is added to increase the boiling point of the medium (from 337 °C to 373 °C) . Chemical decomposition of the sample is complete when the initially very dark-coloured medium has become clear and colourless.

The solution is then distilled with a small quantity of sodium hydroxide, which converts the ammonium salt to ammonia. The amount of ammonia present, and thus the amount of nitrogen present in the sample, is determined by back titration. The end of the condenser is dipped into a solution of boric acid. The ammonia reacts with the acid and the remainder of the acid is then titrated with a sodium carbonate solution by way of a methyl orange pH indicator.

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In practice, this analysis is largely automated; specific catalysts accelerate the decomposition. Originally, the catalyst of choice was mercuric oxide. However, while it was very effective, health concerns resulted in it being replaced by cupric sulfate. Cupric sulfate was not as efficient as mercuric oxide, and yielded lower protein results. It was soon supplemented with titanium dioxide, which is currently the approved catalyst in all of the methods of analysis for protein in the Official Methods and Recommended Practices of AOAC International.

And Velp Scientifica also has an explanation of his method, which is still in use today.

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Kjeldahl (center) in his laboratory.