Meet Pasteur and See How Understanding Microbes Changed Lives for the Better
Part 1: the savior of beet, wine, and silk industries
Pasteur’s Youth, From Boy to Chemist
As a boy in the 1820s, Pasteur grew up in Arbois, France. He spent a lot of time in books and had the ambition to teach other boys. He became an instructor and then an assistant teacher in Bezançon. His father sent him to Paris to the prestigious Normal School, where he resolved to do great things but was soon brought back by strong homesickness.
Later, he went back to Paris and discovered Chemistry under the Mastery of Dumas. Pasteur’s good friend Chappuis, a mere student of philosophy, had to listen for hours to Pasteur’s lectures on the crystals of tartaric acid, and Pasteur told him, “it is sad that you are not a chemist too.”
“He would have made all students chemists just as 40 years later he tried to turn all doctors into microbe hunters” — Paul De Kruif, in Microbe Hunters.
At 26, Pasteur made his first great discovery — isomers of tartaric acid. He was made Professor at Strasbourg University and married the dean’s daughter, who admired him supremely. The Man was all absorbed in his work.
“I am on the verge of mysteries and the veil is getting thinner and thinner. The nights seem to me too long.” he wrote.
Pasteur’s wife waited on him days and nights. She was awed at him and wrote to her father, “You know that the experiments he is undertaking this year will give us, if they succeed, a Newton or a Galileo!” During the whole of Pasteur’s career, his wife would write scientific papers at his dictation and translate his scribblings into her beautiful handwriting. In the words of a friend: “she loved him even to the point of understanding his work.”
The Value of Science for the Industry: of Beetroot Fermentations
Soon, the couple moved to Lille, where Pasteur was asked to demonstrate the value of science by putting it to the service of the industry. “What we want to know is — does science pay? Raise our sugar yield from our beets and give us a bigger alcohol output, and we’ll see you and your laboratory are taken care of”, he was told. Pasteur was fascinated by all that could be done with a potato or a beetroot.
“What we want to know is — does science pay? Raise our sugar yield from our beets and give us a bigger alcohol output, and we’ll see you and your laboratory are taken care of”
A distiller of alcohol from sugarbeet asked Pasteur to the rescue. Some of his batches were good, and some were sick and would make acidity as found in sour milk instead of producing alcohol. So Pasteur set way to the distillation tanks, collected samples, and started observing them under the microscope. He found the yeasts described by Cagniard de la Tour, who had published in 1837 that yeasts are needed for barley to change into beer: “It must be their life that changes barley into alcohol.”
“It must be their life that changes barley into alcohol.” — Cagniard de la Tour
In the bad vats, Pasteur saw confused masses, gray specks much smaller than the yeasts. “Those little rods in the juice of the sick vats are alive, and it is they that make the acid of sour milk.” he observed. “In spite of their miserable littleness they did giant’s work, the work no giant could do — of changing sugar into lactic acid.” So Pasteur started cultivating the little beasts, seeking the right nutrient mix and waiting anxiously for growth each time. And then, the grey specks arrived, and Pasteur became deaf and dumb and blind to the world of men, entranced before his little incubator. Every time they were present, they made the acid of sour milk. So he said to Mr. Bigo, the distiller:
“Keep the little rods out of your vats and you’ll always get alcohol” — Pasteur to Mr. Bigo, to save his beetroot alcohol production.
Enthusiastically, Pasteur told his classes about the great discovery that infinitely tiny beasts could make the acid of sour milk from sugar — an endeavor no man had ever done or would do himself.
From Beets to Wine to Pasteurization
Pasteur had the intuition that the same would happen to wine:
“It is those yeasts that my microscope showed me in the healthy beet vat that turn sugar into alcohol — it is undoubtedly yeasts that make beer from barley and it is certainly yeasts that ferment grapes into wine — I haven’t proven it yet, but I know it.” — Pasteur.
Pasteur was made Director of Scientific Studies in the Normal School, so he and his wife left for Paris — only to discover there was no place and no material. But he made room for his studies and checked his intuitions by testing growing media and repeating the observation that the yeasts were always making alcohol. Dull but necessary work.
Looking into the troubles of wine through the microscope, he learned to associate every defect of the wine — bitter, ropy, rusty — with the wee wrongdoers. He organized a blind test in which winemakers proposed different wines, and Pasteur could predict their defects just by looking through the lens. The group tried to trick him and put a bottle of perfectly good wine in the samples — which Pasteur, to everyone’s shock, recognized as perfectly good.
Did that help the winemakers? Yes, because Pasteur and Duclaux made a recommendation that you certainly have heard about. “If you heat wine just after it has finished fermenting, even if you heat it gently, way below the point of boiling, the microbes that have no business in the wine will be killed, and the wine will not become sick.” This little trick is now known to everyone by the name of pasteurization.
“If you heat wine just after it has finished fermenting, even if you heat it gently, way below the point of boiling, the microbes that have no business in the wine will be killed, and the wine will not become sick.” — Pasteur & Duclaux
Saving the dying silkworm’s industry
Pasteur’s old beloved professor Dumas came from the South of France, from a county that lived by the sales of silk. As silkworms were prey to a terrible disease and the country deperished, Dumas called Pasteur for help. So the Man went and learned about this silkworm pébrine, which covered the worms in black spots, like pepper.
After long observations under the microscope, Pasteur recommended dissecting parent moths after mating, searching for globules in their fatty tissues, and, if they were clean, to keep the eggs. So did the locals, but the next Spring proved to be a disaster — Pasteur’s prophecy was not true. So he made experiments again and watched countless worms curl up and die. Finally, he understood that the globules could be located in any place of the animal and that the parent moth’s whole body should be ground before proceeding to the search for globules. That advice worked, and the next Spring finally brought a splendid abundance of silk.
Dumas and his fellowmen were so grateful to Pasteur that the Mayor of Alès raised a statue in his honor.
Dipping His Moustache in Beer Foam: Pasteur and the Beer Industry
Beer being another form of savvy fermentation, Pasteur set to make French beer better than German beer, training his microscope on the bubbling of a thousand beer vats. He also recommended to brewers to keep invaders out by heating the beer, assuring them this would allow the drink to last longer and be shipped long distances.
But Pasteur hated the taste of beer, which was a big challenge in orienting beer-making towards better tastes. “To his dismay, he discovered that there was much more to the art of brewing than simply keeping vicious invading microbes out of beer vats.” He grew tired of working on beer, but his growing understanding of microbes led him to public health. If keeping the right microbes out of fermentation tanks could keep different types of alcohol production healthy, simple preventative measures in hospitals could lead to a better, healthier future too.
Indeed, Pasteur is not just known for what he did for these industries. The invention made him a hero of vaccination — a long and dangerous endeavor that saved countless lives and forever changed our civilization's future. Follow me to discover in my next article how Pasteur’s work on microbes made unprecedented contributions to public health.
The details and quotes are from the 1926 book Microbe Hunters by Paul De Kruif, who retraces the discoveries and characters that made the beginnings of Microbiology. De Kruif is a fantastic storyteller who learned the intimacy of those early scientists — if you like this chronicle, I recommend you read the whole book!
