Back To CourseMicrobiology 101: Intro to Microbiology
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Angela has taught college Microbiology and has a doctoral degree in Microbiology.
Quick show of hands: How many of you are wearing denim jeans? Quite a few. Keep your hands up, and let's add in anyone that even owns a pair of jeans. That looks like just about everybody. My hand is up, too. What started as tough, resilient pants made from tent material and worn by gold miners has morphed into a major wardrobe staple worldwide. But, this is a lesson about microbiology, not fashion. So, there must be a link, right? Truth be told, there have been more microbes in your jeans than you would probably like to admit. Take them away, though, and your jeans would look a bit different, likely cost you more, and be much worse for the environment.
Let's continue by again looking at your jeans. It's interesting to note that, today, the iconic blue jeans would not be blue without bacteria. The dye used to make jeans and many other products blue is indigo. Indigo is a natural, plant-made dye with a distinctive blue color. Indigo has been used to dye clothing for thousands of years and used to be a rare and very valuable commodity. The problem with indigo, though, is that it can vary a lot from plant to plant. When individually dying your tunic in Mesopotamia, it isn't really a problem if every tunic looks a bit different. When a large blue jean company wants to make large batches of jeans for sale that are exactly the same, you can see how variability could be an unwanted challenge.
Around 1900, a German chemist successfully made synthetic indigo using chemicals. This dye was always consistent, but not suitable for large scale manufacturing due to the high cost, low yield, and intensive labor required. Over the next several years, the process evolved, and manufactured indigo overtook natural indigo as the dye of choice. When you chemically synthesize something, you end up with unwanted chemicals and waste products contaminating your final product; in this case, the indigo dye. So, there was always motivation for coming up with a better way.
Here comes the microbiology. Indigo is a natural product, so its production in plants must be controlled by genes. Genetic engineering is the process by which scientists modify the genome of an organism. Through genetic engineering, it is possible to insert the gene for producing indigo into a bacterial species and then let the bacterium make your indigo. This process ensures consistent results without all the chemical wastes and byproducts.
As an interesting side note, a group of scientists recently discovered a species of bacteria living in the oil-soaked soil of a car garage that was able to break down diesel fuel into indigo. Maybe in the future, your jeans will not just be dyed by bacterial indigo, but that indigo will have come from bioremediated diesel fuel.
OK, so let's say hypothetically, your favorite jean company now has cotton denim dyed blue by waste diesel indigo. But, the fabric is way too tough and stiff to wear. This is where stone washing comes in. Jean manufacturers toss the denim into large rotating drums with stones. As the drum rolls, the stones beat and break the stiff cotton fibers, loosening up and softening the denim. But, this process is rife with difficulties. As with the plant-based indigo, there is no uniformity among individual pairs of jeans. Some are too beaten, others are still too stiff. Some pairs have become damaged, frayed, and ripped. There is too much waste and not enough control over the process.
To add some level of control, acid washing was invented. Instead of stones, acids were added to the materials to break down the cotton fibers and soften the denim. Like the synthetic indigo, acid washing introduces chemicals to the jeans that need to be thoroughly washed out and disposed of.
Once again, microbiology to the rescue! Cotton is a natural fiber made primarily of cellulose, the carbohydrate building block of plant cell walls. But, cellulose is not indestructible. In fact, there are many organisms that produce cellulase, an enzyme that specifically breaks down cellulose. The fungi aspergillus and trichoderma are great sources of industrial cellulase. Instead of stones and chemicals, all the jeans need is a good shot of fungal cellulase. The enzyme will predictably soften the material, depending on how much is added and how long it is in contact with the cotton. Biostoning, using cellulase to soften cotton fabrics, has taken the place of stone and acid washing, without all the variability, damage, and harsh chemicals.
So, our jeans are now bacterially blue and fungal cellulase softened, but not quite ready for sale. Even though we've dramatically reduced the pollution by eliminating chemically-synthesized indigo and harsh acid washes, we still have some troubling contamination on our fabrics that needs to be removed. Our cotton was probably grown with added pesticides. Other dyes might have been added to shift the colors or produce red, black, or green jeans. Or, maybe the fabric was treated with bleach. We need a way to get rid of all these chemicals. Maybe we can use microbes to do the dirty work for us?
Bioremediation is the use of organisms to metabolize pollutants. There is a great lesson entitled Bioremediation: Using Microbes to Clean Up the Environment dedicated to this topic, so for now, we'll just briefly hit on how it applies to the clothing industry.
An estimated 2-50% of the dye added to clothing is lost as waste. Before the serious push towards green industry, the dye-contaminated waste water was simply piped into waterways. In addition to altering the color of the water, many dyes are toxic and carcinogenic, not only to you, but to the organisms that live in and around the water.
Luckily, there is a group of bacteria known as actinobacteria that naturally produce enzymes that break down and decolorize many common dyes. Instead of directly piping the waste water into the streams, many environmentally-conscious companies are pretreating it with mixtures of bacterial species to degrade as much dye as possible. The resulting water is not only cleaner, but it costs much less to use bacteria than it does to chemically and physically remove the pollutants and store the waste.
And, bioremediation can be applied to other pollutants as well. There are currently microbes being used to break down the toxic bleach compounds as well as the pesticides. Through genetic engineering, new mutant microbial species are being investigated every day that work faster, degrade more efficiently, and tackle new pollutants.
It's time to review.
The field of microbiology has been steadily creeping into other areas of human life. One of the latest to embrace the contributions of microbes is the clothing industry. Indigo, a commonly used fabric dye that gives jeans their characteristic blue color, is almost exclusively made by bacteria, instead of chemically synthesized or extracted from plant material.
The fungal enzyme cellulase is used to break down cellulose in cotton fabrics and has taken over for unpredictable stone washing and caustic acid washing during the softening process. This enzyme has the advantages of being nonpolluting and highly predictable.
Pesticides, dyes, and cleaning chemicals have long been a source of pollution in the clothing industry. Recently, environmentally-conscious companies have turned to bioremediation, or using microbes to metabolize pollutants, to deal with these unwanted compounds. The bacteria can naturally break down and eliminate most polluting compounds, leaving our waterways much healthier.
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Back To CourseMicrobiology 101: Intro to Microbiology
20 chapters | 207 lessons