For most of my life, I’ve been playing a small but meaningful role, advocating for the use of bamboo and other renewable resources. I operated two small businesses in the small town of San Luis Obispo, using them as a platform to raise awareness and inspire optimism about bamboo, hemp and other sustainable materials. My activities haven’t quite kicked off the kind of eco-spiritual revolution I was hoping for, but I feel satisfied with my small contributions. At the same time, I’ve noticed other, even smaller agents, making their own important contributions. I’m talking here about Zymomonas mobilis.
Zymomonas mobilis is an anaerobic, waterborne bacterium sometimes found as a contaminant in alcoholic beverages like beer and cider. This microbe plays a key role in the production of ethanol, secreting enzymes that aid in the degradation and fermentation of sucrose and other sugars. In some ways Z. mobilis is superior to yeast, capable of higher sugar uptake, making it one of the most promising players in the field of bioethanol. However, it’s unclear how effective this bacteria is in breaking down cellulosic sugars like xylose, which are present in bamboo and other non-food biomass.
Exciting innovations in bioethanol
The future of our planet depends on a series of major innovations, largely related to how we produce energy. For decades we’ve understood that cheap petroleum is not only limited but also environmentally destructive. Since the middle of the 20th century, this black gold has been running our cars and generating our plastics. It’s also been fueling the Greenhouse Effect and an unending spate of armed conflicts in the Middle East.
Every day the need for a greener energy source grows more dire, and a range of alternatives are well within reach. But further research and development are necessary to close the gaps that have kept those alternatives from being adequately efficient and cost-effective.
Eyes on the Prize: X marks the spot
At last, thanks to a combination of global necessity and some privately sponsored incentives, the race is really on. I’m talking, of course, about Elon’s Musk $100 million X-Prize. The high-profile billionaire is offering this unprecedented nine-figure reward to whoever can develop the best technology to “pull carbon dioxide directly from the atmosphere or oceans ultimately scaling massively to gigaton levels, locking away CO2 permanently in an environmentally benign way.”
Bamboo has been capturing and converting CO2 into oxygen for millions of years. But in this era of climate crisis, we need a more potent remedy to reverse the deleterious effects of runaway industrialization. Bamboo can and should play a pivotal role, alongside other, more ambitious technologies.
Besides the X-Prize, designed to remove carbon, another “green race” is underway to develop cleaner fuel, to stop pumping carbon into the atmosphere. Even without Musk’s enticements, we all recognize the enormous economic potential of a truly competitive and renewable energy source.
This is part of why so many chemical and biotech firms are working to make cellulosic ethanol processing — the kind used with non-food crops like bamboo — more effective and efficient, with more processing plants and better enzymes.
Currently, the main source of bioethanol are food crops, mostly corn. Simply put, yeasts (such as Saccharomyces cerevisiae) are used to break down the sugars and ferment them into ethyl alcohol, releasing some carbon dioxide as a bi-product. It’s a fine alternative to refining petroleum, but using food crops for energy leads to a whole other set of problems. These include driving up food prices and tying food shortages to energy shortages.
The alternative to generating fuel from food is to make it from crops like bamboo and timber. Essentially, this means fermenting cellulose, instead of glucose, fructose, and sucrose. This process is known as cellulosic ethanol.
In the US, where bamboo farming remains more of a novelty, poplar trees provide the primary material for cellulosic ethanol. But turning trees into ethanol actually ends up producing more carbon in the long run. The trees take decades to replace, and their carbon sinks are released when they get cut down. Not so with bamboo, whose durable rhizome roots can retain the carbon if the plantation is properly managed.
Currently, there are about 21 cellulosic ethanol plants in the US, either operational or under construction, covering just about every region of the country. Some of the plants rely on grasses as their feedstock, others on wood chips or multiple sources. One plant in Florida is making ethanol from citrus peels. Several such plants are now operating in Europe as well.
Bacterial enzymes for bamboo fermentation
I’ve already explained the benefits of using non-food crops for ethanol production, but there are challenges with cellulosic ethanol as well. Most importantly, wood and bamboo are much harder than corn, requiring a bit more work to break them down. And more technically speaking, cellulose is very high in lignin and C5 sugars like xylose and arabinose.
The latest methodology for converting bamboo into ethanol fuel uses a bacteria called Zymomonas mobilis. As an alternative to yeast-based fermentation, this microbe can capture nitrogen from the atmosphere, take in more sugar, and produce ethanol more quickly than traditional methods. This proves to be a superior process for breaking down most sugars. But Z. mobilis still has a hard time with xylose, the chief component of lignocellulose, which gives trees and bamboo their woodiness.
Innovating with Zymomonas mobilis for biofuel
The need for greener fuel sources has been motivating scientists around the world to study the fermentation of lignocellulose more closely. That has meant conducting exhaustive research to compare the feasibility of Zymomonas mobilis and Saccharomyces cerevisiae, more commonly used in yeast fermentation.
Scientists are now taking it to the next level, modifying Z. mobilis so that it can digest lignocellulose and C5 sugars more effectively. While some people have legitimate concerns about genetically modified salmon or mosquitoes, manipulating the genes of single-celled bacteria is pretty safe and simple.
Even as we speak, scientists are working busily over their Petri dishes to create new varieties of Z. mobilis that can tolerate higher levels of acidity. This makes the bacteria more useful for fermenting cellulosic biomass which is commonly pretreated with acid.
Modified bacteria doesn’t get the same publicity as Elon Musk, but in the world of bio-ethanol, this is a pretty big deal. For those of us who can get excited about single-celled organisms, this is about as exciting as it gets.
Knowledge is power
If you’re as fascinated with bamboo ethanol, Zymomonas mobilis, and bacterial enzymes as we are, this is just the tip of the microbial pyramid. Check out some of these other fascinating articles to learn more.