If you stop and think about it, the Industrial Revolution was inextricably intertwined with a chemical revolution.
Chemical energy – generated by burning coal or gasoline, for example – enabled new modes of transportation and automated making goods into faster, cheaper, and more reproducible processes at larger and larger scales.
More efficient transportation and manufacturing processes, in turn, allowed us to generate new types of materials and products. For instance, think of everything you have used today that is made out of plastic - I bet that’s a lot of objects!
However, there are numerous environmental consequences due to this unprecedented industrial production: rapidly increasing climate change, landfills and oceans overflowing with disposable single-use products, and rampant chemical pollution, to name only a few.
Purified proteins are important tools that make existing industrial chemical reactions more environmentally friendly, and protect the environment by degrading plastic waste, detecting and cleaning up chemical spills, and providing renewable sources of energy.
In this article we will dive deeper into the exciting and emerging industrial and environmental applications of purified proteins and enzymes.
Article Table of Contents
Chemical Applications
These processes do not strictly require enzymes; however, proteins replace harsh chemical reagents making the production process as well as the final products more environmentally friendly.
One downside of using enzymes is that they can be more expensive than the harsh chemicals they replace. However, this downside is mitigated by reusing enzymes over multiple reactions, and by optimizing enzymes to be more active and stable.
Novel enzymes that catalyze new reactions with industrial applications are also being invented all the time! These novel enzymes introduce new chemistries never observed in nature, making the new enzymes a type of modern-day alchemy!
Paper
Even in our increasingly digital world, we still use many paper products every day! From printouts to receipts, toilet paper to disposable coffee cups, our life would be very different without these crucial supplies.
Wood is mechanically and chemically degraded into pulp, which is then processed to make paper products. Proteins play key roles in the degradation process as lipases degrade pitch from the wood, and xylanase enzymes bleach the wood pulp to color paper white.
Traditionally, both steps used toxic chemicals instead of enzymes. However, enzymes reduce the amount of toxic chemicals needed. This makes the overall process more environmentally friendly as enzymes are rapidly biodegradable and do not accumulate in the surrounding environment, unlike toxic chemicals.
New paper can also be generated by recycling old paper. During this process the old paper is first deinked to remove the prior ink and coloring. Compared to chemical processes alone, deinking with enzymes is more efficient and results in a higher brightness for the resulting recycled paper (Bajpai, 1999).
The enzymatic process is also more adjustable allowing the deinking process to be fine-tuned to more efficiently remove different types of ink depending on the source paper being recycled.
Cleaning Products
Aren’t you glad that we don’t have to wash all of our clothes and dishes by hand anymore? The soaps and detergents that we use today to remove stains and clean laundry, dishes, and other household items contain numerous purified enzymes!
Like paper processing, substituting enzymes limits the amount of harsh chemicals that are used in detergents. This means that enzyme-containing soaps are more environmentally friendly because they contain biodegradable ingredients. Additionally, enzymes are more adaptable than chemicals, and slight variants tune the enzymes properties to optimally clean under a variety of different conditions.
In the early 20th century, laundry detergents first used trypsin, a protease extracted from the pancreas of pigs (Infinita Biotech, 2020).
However, trypsin has weak activity and stability in laundry conditions where surfactants and other detergent molecules inhibit trypsin activity.
Over the years novel variants of trypsin were derived that are more compatible with chemical detergents. Further variants have been optimized to work best in the lower wash temperature common in European laundry, for example.
In addition to trypsin, laundry detergents also use hydrolases, lipases, amylases, mannases, cellulases, pectinases, and other proteases (Table 1).
Biocatalysts
Most examples given in this article are of proteins or enzymes catalyzing a reaction such as processing wood into paper or recycling plastic. In this scenario, biological molecules (proteins) are used to catalyze the chemical reaction, which we term biocatalysts.
Many of these chemical reactions can be performed with a nonbiological catalyst by using other types of catalysts. Often these catalysts come in the form of metals and frequently require harsh chemical conditions to make the reactions proceed. By replacing metal catalysts with biocatalysts these reactions are more environmentally friendly.
However, perhaps even more exciting is that enzymes are being discovered, and designed to carry out new chemistries.
Think of it like building a house. Metal-catalyzed reactions are like a hammer and nail. You can do a lot of work with a hammer and a nail – one could probably even build most of a house. But it is going to be a lot harder to build the house, and the house will probably be lower quality than if you had additional tools at your disposal like screwdrivers and wrenches, for example.
Newly discovered and designed enzymes do just that – they expand the available toolkit to build molecules with important industrial and health applications.
These newly-invented chemistries enable the production of a number of important medicines and tools including:
- The antidepressant levomilnacipran (Wang et al., 2014).
- Ticagrelor, a medication that prevents the reoccurrence of heart attacks (Hernandez et al., 2016).
- The diabetes medication sitagliptin (Savile et al., 2010).
- Medical imaging agents (Kan et al., 2016; Kan et al., 2017; Onega et al., 2009).
Environmental Applications
Our world faces many pressing environmental challenges including overflowing landfills and aquatic garbage patches, pollution spills, and non-renewable energy sources.
Purified enzymes offer new solutions to these environmental issues, and the solutions provided by enzymes will continue to grow as more and more bespoke proteins fit for specific issues are designed.
Similar to the industrial processes discussed above, there are alternative strategies for executing each of the environmental applications listed below.
For example, metal catalysts can be used for plastic degradation, bioremediation, and biofuel production reactions described below. Furthermore, small organic molecules are predominantly used as pesticides.
However, proteins offer unique advantages in each of these areas, including:
- Enzymes generally work under more environmentally friendly reaction conditions compared to metal catalysts.
- Enzymes are biodegradable and do not accumulate in soil and ground water unlike metal catalysts and organic small molecules.
- Natural enzymes often have higher activity and specificity than metal catalysts, and are experimentally improved to further enhance these inherent advantages.
Let’s go over the exciting ways in which enzymes are being
used to attack these pressing environmental problems!
Degrading Plastics
Plastics take hundreds of years to degrade, piling up in landfills and in ocean garbage patches.
Fungal enzymes degrade plastic waste. Yet, the real-world application of these enzymes are limited by the conditions (pH, temperature, etc.) under which these natural enzymes are stable and active.
Researchers recently evolved a new poly(ethylene terephthalate) (PET) hydrolase to enhance enzyme activity over a broad range of pH and temperatures (Lu et al., 2022).
This enhanced hydrolase also degrades a wider variety of plastic products. Previously, long PET plastics could not be recycled. However, enhanced PET hydrolases break down these plastics into smaller bits that are then recycled into new plastics (Figure 1).
Therefore, these enzymes have a striking potential to reduce plastic waste, as well as the amount of new plastic that needs to be made from scratch.
Figure 1. PET hydrolase (left, PDB:6IJ6) and depolymerization of poly(ethylene terephthalate) reaction that it catalyzes (right). Residues mutated to stabilize and activate PET hydrolase shown in sphere format.
Bioremediation
The widespread use of industrial chemicals, combined with poor waste management plans and accidental spills resulted in an overabundance of polluted sites.
In Europe alone, it is estimated that over 300,000 sites are contaminated with chemicals (Eibes et al., 2015).
Purified proteins aid in detecting and cleaning up pollutants including pesticides, oil/fuel spills, and heavy metal contamination.
Proteins that specifically bind to pollution chemicals are used as biosensors where contamination occurred. Compared to other detection strategies, protein biosensors:
- Are very specific and selective for chemicals.
- Detect a wide range of chemicals by using different proteins.
- Provide flexibility in detection methods.
- Minimize false detection.
Protein biosensors are frequently used to detect heavy metals, organic pollution, and pests including:
- Mercury, copper, and cadmium in river water.
- The pesticide atrazine in drinking water.
- Methyl salicylate, a biomarker for crop pathogens.
Enzymes also degrade pollutants into less harmful products to clean polluted sites. For example, enzymes degraded spilled airplane fuel at the Thule Air Base in Greenland. Using enzyme degraders, along with a few additional steps, resulted in a greater than 95% reduction in fuel contamination at the air base (Vinson and Garret, 2000).
Different enzymes specifically degrade unique pollution chemicals. In addition to airplane fuel, distinct enzymes have degraded the following pollutants in real-world scenarios:
- Almond tree pesticides in groundwater.
- The pesticide DDT from soil.
- Petroleum toxic byproducts from soil.
Biofuel Production
Currently, most cars and trucks use gasoline as fuel. Gasoline is processed from oil, a limited and nonrenewable natural resource that was generated over millions of years.
Extraction from oil fields is destructive to the surrounding environment. Furthermore, the limited number of operating oil fields also means that oil is frequently shipped around the world to its final destination.
Fortunately, great progress has been made on developing locally-sourced and renewable biofuels. Perhaps the most exciting example of this is using biowaste, such as used cooking oils, to generate biofuel that power our cars just like gasoline.
Proteins are critical in generating biofuels. For example, phospholipases and lipases are two key enzymes that generate biodiesel from cooking oils. Phospholipases remove the phosphate head group from phospholipids, turning them into diacylglycerol. Lipases cut free fatty acids into fatty acid methyl esters, an important ingredient in biodiesel.
Compared to gasoline, biodiesel has the advantages of being generated from renewable resources and being produced locally instead of shipped across the world.
However, a disadvantage of biodiesel production using enzymes is the relatively high cost in comparison to regular diesel. Scientists are currently developing enzyme variants that are more active, more stable, and reusable, which will help lower the overall cost.
Biopesticides
Six billion pounds of pesticides are used each year to efficiently grow crops to produce food, oil, and fibers (Sabry, 2020). Pesticides are traditionally made from stable chemicals that contaminate the surrounding soil and groundwater.
New protein-based pesticides protect against insects, fungi, and other threats. Importantly, protein biopesticides are readily biodegradable making them safer for the environment and for human health.
A promising example of a biopesticide is EvocaTM, which protects strawberries, grapes, and other high value crops against fungal rot.
Field trials showed that EvocaTM more effectively prevents fungal rot than chemical fungicides (Biotalys, 2023). Additionally, EvocaTM is more environmentally friendly because it rapidly degrades and doesn’t accumulate in soil and the surrounding groundwater like chemical pesticides.
EvocaTM is currently being evaluated by the US Environmental Protection Agency. There are exciting results so far, and the inherent environmental advantages of biopesticides suggest that they will likely make up an increasing portion of pesticide usage for a wide variety of crop pathogens.
Table 1. Proteins involved in industrial and environmental applications
|
Protein |
Function |
Application |
|
Hydrolase |
Catalyze bond cleavage with water |
Paper, Cleaning, Plastic, Biofuel |
|
Lipase |
Hydrolyze lipids |
Paper, Cleaning |
|
Glycosidase |
Hydrolyze oligosaccharides |
|
|
Xylanase |
Xylan glycosidase |
Paper |
|
Protease |
Hydrolyze proteins |
Paper, Cleaning |
|
Amylase |
a-1,4 glycosidase |
Paper, Cleaning, Biofuel |
|
Trypsin |
Protease cuts after basic residues |
Cleaning |
|
Mannase |
Mannose glycosidase |
Cleaning products |
|
Cellulase |
Cellulose glycosidase |
Cleaning products |
|
Pectinase |
Pectin glycosidase |
Cleaning products |
|
PET hydrolase |
Hydrolyze PET plastics |
Plastic |
|
Phospolipase |
Hydrolyze phosphate group off lipids |
Biofuels |
So, there you have it – purified proteins enable new
chemical reactions, make existing industrial chemical reactions safer for the
environment, and detect and clean up environmental pollution.
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