EXERCISE 17 MAKEUP: IS ETHANOL A SUSTAINABLE SOLUTION TO OUR ENERGY NEEDS? INTRODUCTION Throughout history, humans have discovered numerous ways to actively use other organisms for our own benefit. In fact, it is safe to say that without these other species, the global human population would not be nearly as large as it is today1. Many of the organisms that have greatly (positively) impacted human history are obvious (e.g. wheat, rice, cows) and their benefits are obvious too (food sources.). However, others are not so conspicuous. The first microorganisms manipulated by humans for their own gains were yeasts2. Much like their larger counterparts, yeasts have played a large role in human food systems for millennia, most notably in bread and beverage making. Yeasts are prolific, hardy, and versatile microorganisms –and they love carbohydrates! Yeasts have the ability to process sugars in two ways, employing a different metabolic pathway depending on whether oxygen is present in their environments. In the presence of oxygen, they undergo respiration; in the absence of oxygen, yeasts utilize an alternative metabolic pathway –fermentation. This effervescent reaction is what makes breads rise (CO2) and “adult beverages” so intoxicating (ethanol). Yeasts’ benefits for humans extend well beyond our gustatory hankerings. Ethanol –the most notable byproduct of fermentation– has many uses besides its intoxicating effects. Historically, humans have used it as everything from a sterilizing agent to an aphrodisiac (some uses were based on faulty logic). More pertinently, in the last 150 years, humans have developed this resource as a fuel to power internal combustion engines for our transport. In fact, the first Model T Ford ever produced ran on ethanol. Ethanol production has increased rapidly in the U.S. in the last 25 years in an effort to create cleaner burning gasoline blends, and most recently to decrease dependence on fossil fuels for its energy needs. Furthermore,…