When the word “microorganisms” pops up in a conversation it can trigger multiple perceptions. To some, the first thing that comes to mind are diseases. [Salmonella, influenza, Candidiasis...] To others, microorganisms remind them of nutritional yeast, baking, and of course, alcoholic beverages like wine and beer (oh, La vie Boheme).
There are few others, however, that picture something entirely different when thinking about microorganisms: microfactories. Even though I am a huge (and I mean HUGE) fan of whisky, beer and company, I consider myself in this last group. Microorganisms are incredible. They can adapt to extreme conditions, have survived multiple extinction events, and are even responsible for the change in atmospheric gas composition that allowed for life as we know it on Earth.
Psychedelic microbes hard at work!
The number of microorganisms studied so far opens the door to the vast capabilities they exhibit. Just in the last decade, the most revolutionary tool in gene editing, the CRISPR/Cas9 system, was developed after studying the adaptive microbial immune system. And it is only the tip of the iceberg. We don’t know what we don’t know, but we know there are hundreds of microbial species we don’t know, you know?
If microbes were politicians I have no doubt that Saccharomyces cerevisiae would be leading the polls, followed very closely by Lactobacillus acidophilus and some of its lacto-cousins. However, I want to further explore the amazing roles available to microorganisms in our industry. From fermentation in food and beverages, to the production of bioenergy and bioplastics, our industry benefits immensely from microbial machineries. The following list provides some of my very personal favorite examples of how these tiny guys can make a huge impact in our industry.
Bacterial Cellulose
Lignocellulosic biomass, or plants that produce hard wood, is rich in cellulose, a fiber composed of multiple glucose molecules (a.k.a. polysaccharides). For decades our industry has benefited grandly from these fibers, with paper being the most popular application. Other uses of cellulose include composites, biocompatible materials, and about 80% of the textile fibres produced in the world are based on cellulose or polyester.
Another advantage of cellulose is that it can be modified through chemical alteration to obtain or improve specific capabilities. For example, cellulose in its natural form can serve as an adsorption material; however, the adsorption capacity of cellulose can be drastically improved with chemical modifications. In fact, cellulose can be a precursor to form activated carbon, the most popular and highly efficient adsorbing material.
Cellulose is great, and we keep on learning new ways to use it. So why bring bacteria in the equation? The extraction and purification of cellulose from plants can be expensive, with large requirements of energy, harsh chemicals, and the use of expensive enzymes.
Machinery to synthesize cellulose (cellulose synthase operon in technical terms) has been found in the genome of several bacteria. These bacteria synthesize cellulose to facilitate the formation of biofilms, and in cases of pathogenic bacteria, colonization of a host. Therefore, these bacteria have the capacity to produce cellulose, and then secrete it out of their cell, simplifying the commercial production of cellulose drastically.
Many reports exist on the efficient use of bacterial cellulose, including biomedical applications, drug delivery, food, cosmetics, and emulsion stabilization, amongst others.
Bioplastics
Similar to the case of bacterial cellulose, some bacteria can naturally synthesize polyhydroxyalkanoates (PHAs) and polyhydroxybutyrates (PHBs). PHA and PHB are amongst the most popular bioplastics as they have similar physical properties than petrochemical plastics, are biodegradable, and biocompatible.
PHA- and PHB-producing bacteria accumulate these bioplastics in storage granules inside of the cell (in the cytoplasm), and usually they don’t follow a strict diet. In fact, there have been reports of these bacteria thriving in municipal sewage, fish solid waste, food waste, and plant-based waste. So with these bacteria we can literally convert waste into bioplastics!
Now lets talk about a different type of microorganisms: microalgae. Microalgae are photosynthetic microorganisms, which means they can convert atmospheric CO2 into sugars though photosynthesis. One of the main energy storage reserves microalgae produce is starch, another polysaccharide formed with glucose. Starch accumulates in granules in several compartments of the cell (cytoplasm and chloroplast), and depending on the species starch content can account to most of the cellular weight. Researchers have preformed a direct plasticization of microalgae biomass into starch-based bioplastics. In addition to starch, proteins and other polymers in microalgae biomass have been converted to bioplastics through a process called electrospinning, in which polymers can be manipulated by the use of electric fields. Through the appropriate optimization of these processes, microalgae biomass can be turned into several types of bioplastics, not to mention the immense benefits this biomass offers… but we’ll get to that in another article.
All of these examples illustrate something bigger than microorganisms producing bioplastics: we can turn waste into plastics. In my opinion this a perfect example of how sustainable development can look like in our society. What do you think?
CO2 Biosequestration
Perhaps you have heard the term ‘carbon sink’, a natural system where large quantities of atmospheric CO2 are stored. Our oceans are important carbon sinks accounting for the sequestration of large amounts of CO2, storing it into sugars, fats, and biomass. There are also physico-chemical means of CO2 sequestration in our marine ecosystems, but we’ll focus on the biological means for the purpose of this article. Microalgae (including their cousins cyanobacteria) are largely responsible for the (bio)sequestration of CO2 in our oceans and lakes. In fact, cyanobacteria (photosynthetic bacteria, a.k.a as blue-green algae) are responsible for the change in gas composition that allowed for life on Earth as we know it.
These amazing microorganisms are slowly becoming a macroplayer in our industry. Their ability to photosynthesize makes them ideal for the recovery of CO2 from industrial exhausts. Many cement plants are incorporating microalgae ponds to reduce their CO2 emissions and later utilize the biomass to produce biofuels. Not only do they consume CO2 from the atmosphere, which is one of the greenhouse gases of most concern in our society, but they can also get the rest of their nutrients from wastewater. Most wastewater treatment pants include what is called a ‘tertiary treatment’ where nitrogen and phosphorous are removed. Several studies have demonstrated the feasibility of incorporating a microalgae treatment process in a wastewater treatment plant, where nitrogen and phosphorous species are consumed by microalgae instead of using chemicals.
From bioenergy and bioplastics, to biofertilizers and nutraceuticals, microalgae biomass opens a world of possibilities for the reduction of CO2 emissions, and the conversion of waste streams into products.
Renewable Natural Gas
Biogas is composed of methane (≈ 50-70%), CO2 (≈ 25-50%), and other constituents (≈ 10%). It is the main product from the anaerobic digestion (in the absence of oxygen) of organic waste by bacteria. The process of anaerobic digestion is a key player for the treatment of many industrial wastes, including wastes from dairy farms, industrial and municipal wastewater, pulp and paper mill wastes, and lignocellulosic biomass.
Biogas in itself can be used to produce energy, but it can be upgraded to biomethane, a.k.a. renewable natural gas, by converting the CO2 in biogas into methane. Renewable natural gas (RNG) can be injected into the existing natural gas pipelines, as both fuels are interchangeable. In Ontario, we can certainly expect to hear more talks about RNG from the new team at Enbridge Gas Inc.
Yet another way in which microorganisms can turn waste into energy, revealing a little bit of a trend here, wouldn’t you say?
Biofertilizers: microorganisms in farming
We have mentioned several examples of how bacteria and microalgae can play important roles turning different types of waste into products like energy and plastics. Now it is the time to talk about fungi.
As we expand our understanding of agriculture, the importance of microbial communities in soil becomes more evident. There are many microorganisms that form associations with the rots of plants, where the microbe provides nutrients and protection to the plant, and in exchange the plant provides sugars, or photosynthate, to the microbes. It is a very neat relationship that has huge implications on the crop yields at harvest.
It would be impossible to talk about every single example of these plant-microbe interactions in this article, so I want to focus to one of my favorite ones: arbuscular mycorrhizal fungi (AMF). AMF is a diverse group of fungi, and it has been found that more than 80% of land plant species. Through this mutualistic association AMF can take inaccessible forms of nitrogen and phosphorous from the soil and turn them into forms that are accessible for the plant, which has earned AMF the title of biofertilizers. This becomes of increasing importance as our finite resources of phosphorous could be depleted soon if we don’t do anything about it. Additionally, AMF can help maintain a healthy soil aggregation and support the plant during drought stress conditions. How is this relevant in our industry? Let’s take my absolute favorite vegetable as an example; AMF has increased tomato yields by about 25%... That is 25% more pizza! I mean, not really, but you get my point.
AMF’s potential, however, extends beyond crop yields. These microorganisms also play a significant role in phytoremediation, the use of plants to remediate a contaminated site, and there is evidence showing that AMF can enhance the production of biomolecules in plants, such as vitexin with its many pharmacological effects.
Photo by Michael Schiffer on Unsplash
Here we have explored only five examples of diverse roles that microorganisms can play in our industry. It is my hope that this article provides a little bit of context as to what microorganisms are capable of, and perhaps with a little imagination we will reach a sustainable future were microfactories lead the way.