The Surprising Power of CO2

When most people think of carbon dioxide (CO2), they picture the gas we exhale or its role in global warming. However, CO2 has other surprising uses, one of the most fascinating being its ability to act as an antibacterial agent. That’s right—under certain conditions, CO2 can help inhibit the growth of harmful bacteria. This incredible property is already being used in various industries, including food preservation and medical treatments.

As noted by M. Persson et al. in their study, "Carbon dioxide (CO2) has an inhibitory effect on the growth rate of bacteria even at body temperature. This effect is especially potent against Staphylococcus aureus, a common bacterium responsible for various infections." But how exactly does CO2 work as an antibacterial agent?

Understanding Bacterial Growth

To appreciate how CO2 works against bacteria, it’s helpful to understand what bacteria need to thrive. These tiny organisms multiply rapidly under the right conditions, requiring:

• A food source like sugars and proteins

• Moisture

• Oxygen (for many types)

• A favorable pH level

Most harmful bacteria grow best in environments that are neither too acidic nor too alkaline and thrive between 40°F and 140°F (4°C to 60°C). Disrupting these conditions can stop bacteria in their tracks—and that’s where CO2 comes in.

How CO2 Affects Bacteria

CO2 is an effective antibacterial agent through several mechanisms:

1. Creating an Oxygen-Free Environment

Many harmful bacteria, such as E. coli and Salmonella, require oxygen to grow. By replacing oxygen with CO2, it creates a low-oxygen atmosphere that makes it difficult for these bacteria to survive. This is one of the reasons CO2 is commonly used in food packaging.

As the research from M. Persson and his colleagues highlights, "CO2 significantly decreased the growth rate of Staphylococcus aureus at body temperature," underscoring its effectiveness in limiting bacterial growth.

2. Lowering pH Levels

When CO2 dissolves in water, it forms carbonic acid, which lowers the pH and makes the environment more acidic. Many bacteria struggle to grow in acidic conditions, helping to preserve food and prevent spoilage.

3. Inhibiting Enzyme Function

Bacteria rely on enzymes to perform vital functions like breaking down nutrients or replicating DNA. CO2 interferes with these enzymes, slowing bacterial growth and reproduction, effectively disrupting their ability to thrive.

4. Disrupting Cell Membranes

High concentrations of CO2 can alter the structure of bacterial cell membranes, making them more permeable. This causes essential cell components to leak out, eventually killing the bacteria.

CO2 in Action: Real-World Applications

CO2’s antibacterial properties are already being put to use in several industries. Let’s take a closer look at how this powerful gas is making a difference:

1. Food Packaging

If you’ve bought pre-packaged meat, cheese, or salad, you’ve likely encountered CO2 in action. "Packed in a modified atmosphere," as many labels note, means that the air inside has been replaced with CO2, reducing oxygen levels to slow bacterial growth and extend the product’s freshness.

2. Carbonated Beverages

CO2 isn’t just responsible for the bubbles in your soft drink—it also creates a slightly acidic environment that prevents bacteria from spoiling the drink. That’s why carbonated beverages tend to last longer than still drinks.

3. Medical Use

CO2 is used in surgeries where it’s pumped into the body to create space for operations. This process, called insufflation, helps keep the area sterile as CO2 inhibits bacterial growth and adds an extra layer of protection during procedures.

4. Food Processing & Sterilization

In some food processing facilities, CO2 is used to sterilize surfaces and equipment, penetrating crevices where bacteria may hide. This ensures a clean environment and safer food products.

5. Food Sterilization

Pressurized CO2 has proven to be an effective method for eliminating bacteria and preventing food poisoning. This technique inactivates bacteria in food, with higher pressure and extended exposure times leading to greater bacterial reduction. It is particularly promising for sterilizing heat-sensitive food products.

In 1997, Osman Erkmen conducted research on the antimicrobial effects of pressurized CO2 on Staphylococcus aureus, a bacterium responsible for food poisoning. The study examined the effectiveness of this method in both broth and milk, demonstrating that increased CO2 pressure and longer exposure durations significantly enhanced bacterial inactivation.

6. Water Purification

CO2 enhances water purification by boosting the effectiveness of common disinfectants. It plays a crucial role in regulating pH levels during water treatment by dissolving in water to form carbonic acid, which neutralizes alkaline substances and stabilizes pH. This makes it an eco-friendly alternative to strong acids for improving water quality.

A study explored CO2's potential to enhance the microbial toxicity of widely used antibacterial agents like calcium hypochlorite (Ca(ClO)₂) and hydrogen peroxide (H₂O₂). The researchers found that pre-incubating Escherichia coli K-12 in a CO2-enriched environment significantly increased the effectiveness of these disinfectants in killing bacteria.

This enhanced toxicity is linked to CO2’s ability to stimulate microbial metabolism, making the bacteria more sensitive to the oxidizing effects of Ca(ClO)₂ and H₂O₂. The study highlights a promising, safe, and environmentally friendly method for water purification by combining CO2 with traditional disinfectants (Adrian Garrido, et al., 2019).

7. Wastewater Treatment

In wastewater treatment, CO2 is used to adjust pH levels and aid in contaminant removal. By enhancing biological processes, CO2 helps improve water quality while reducing the need for harsh chemicals.

In 2012, Varsik Martirosyan introduced an innovative and eco-friendly technology for sterilizing water using CO2 bubbles. Known as the Atmospheric Bubbling with CO2 Device (ABCD), this method works by passing CO2 gas through wastewater at atmospheric pressure. The study explored how effectively ABCD inactivates E. coli and MS2 viruses, comparing its performance to other disinfection techniques like UV, ozone, and chlorine.

The results showed that CO2, especially at elevated temperatures, was highly effective in killing both bacteria and viruses, often outperforming air in terms of speed and efficiency. With its potential to reuse exhaust gases from industrial processes, the ABCD method presents an exciting new approach to water purification, reducing energy consumption and minimizing harmful byproducts.

8. Combatting COVID-19

There’s even ongoing research into using humidified, warmed CO2 as a treatment for COVID-19. Early studies suggest that CO2 could help suppress the inflammatory responses associated with the virus, offering a new tool in the fight against respiratory diseases. As El-Betany explored in 2020, CO2's unique properties may offer "a safe and economical tool" for mitigating COVID-19 and related conditions.

Conclusion

CO2 is more than just a gas we exhale—it’s a powerful tool in the fight against harmful bacteria. From keeping food fresh to helping sterilize medical environments, CO2 has a wide range of applications that enhance safety and extend the shelf life of products. By lowering oxygen levels, making environments more acidic, and disrupting bacterial processes, CO2 proves itself as a practical and effective method for controlling bacterial growth. While it may not be a silver bullet for every situation, its use across industries highlights its potential to promote cleaner, safer environments.

Scientific References

Title: Synergistic effect of pressurized carbon dioxide and sodium hypochlorite on the inactivation of Enterococcus sp. in seawater

Author: Dang TT et al.

Link to full text: https://pubmed.ncbi.nlm.nih.gov/27721172/

Abstract: This study investigated the effect of combined treatments using pressurized carbon dioxide (PCD) and sodium hypochlorite (NaOCl) on the inactivation of Enterococcus sp. in artificial seawater. Bacterial inactivation was conducted in a liquid-film-forming apparatus with various pressure conditions, CO₂ supply rates, and chlorine dosages. Combined PCD/chlorine treatments resulted in greater disinfection efficiency than those for the two individual treatments. Synergy values were correlated with pressure and CO₂ concentrations (p < 0.001). Combination of 0.9 MPa PCD (various CO₂ supply rates: 25% CO₂ + 75% N₂, 50% CO₂ + 50% N₂, and 100% CO₂) and chlorine (0.20 mg L-1) yielded average synergy values of 4.9, 5.2, and 4.4 log, respectively, within 3 min. Combined treatment with PCD (100% CO₂, 0.3 MPa, and 20 °C) and chlorine (0.20-0.22 mg L-1) achieved an average synergy value of 4.6 log and complete inactivation (5.2-5.5 log reductions) of Enterococcus sp. within 4 min. In contrast, when the two individual treatments (PCD and chlorine) were used, only 3.7 and 1.8-2.3 log reductions, respectively, were achieved after 25 min. These findings suggest that the combined PCD/chlorine treatment has synergistic benefits and provides a promising method for the disinfection of ballast water.

Title: Antimicrobial Effect of Pressurized Carbon Dioxide on Staphylococcus aureus in Broth and Milk

Author: Osman Erkmen et al.

Link to full text: https://www.sciencedirect.com/science/article/pii/S0023643897902772

Abstract: Studies were carried out to assess the use of high-pressure CO₂ treatment to inhibit Staphylococcus aureus in broth and raw cow's milk at 25 °C. Two phases in the survival curves were observed. The early stage was characterized by a slow rate of decrease in number of S. aureus; this rate increased sharply at the later stage. Staphylococcus aureus suspended in broth was completely inactivated after CO₂ treatment at 7 MPa for 100 min and 8 MPa for 60 min. The sterilization effects of CO2 on both. S. aureus and aerobic bacteria were observed at 14.6 MPa for 5 h and 9 MPa for 2 h in whole and skim milk, respectively. Staphylococcus aureus and aerobic bacteria were more difficult to inactivate when they were suspended in whole milk that may have protected the cell from penetration by CO₂. Reduction rates of S. aureus and aerobic bacteria were sensitive to pressure, exposure time and the suspending medium.

Title: Humidified Warmed CO₂ Treatment Therapy Strategies Can Save Lives with Mitigation and Suppression of SARS-CoV-2 Infection: An Evidence Review

Author: Alaa M. M. El-Betany et al.

Link to full text: https://pubmed.ncbi.nlm.nih.gov/33425942/

Abstract: The coronavirus disease (COVID-19) outbreak has presented enormous challenges for healthcare, societal, and economic systems worldwide. There is an urgent global need for a universal vaccine to cover all SARS-CoV-2 mutant strains to stop the current COVID-19 pandemic and the threat of an inevitable second wave of coronavirus. Carbon dioxide is safe and superior antimicrobial, which suggests it should be effective against coronaviruses and mutants thereof. Depending on the therapeutic regime, CO₂ could also ameliorate other COVID-19 symptoms as it has also been reported to have antioxidant, anti-inflammation, anti-cytokine effects, and to stimulate the human immune system. Moreover, CO₂ has beneficial effects on respiratory physiology, cardiovascular health, and human nervous systems. This article reviews the rationale of early treatment by inhaling safe doses of warmed humidified CO₂ gas, either alone or as a carrier gas to deliver other inhaled drugs may help save lives by suppressing SARS-CoV-2 infections and excessive inflammatory responses. We suggest testing this somewhat counter-intuitive, but low tech and safe intervention for its suitability as a preventive measure and treatment against COVID-19. Overall, development and evaluation of this therapy now may provide a safe and economical tool for use not only during the current pandemic but also for any future outbreaks of respiratory diseases and related conditions.

Title: Virus and bacteria inactivation by CO₂ bubbles in solution

Author: Adrian Garrido Sanchis et al.

Link to full Text: https://www.nature.com/articles/s41545-018-0027-5

Abstract: The availability of clean water is a major problem facing the world. In particular, the cost and destruction caused by viruses in water remains an unresolved challenge and poses a major limitation on the use of recycled water. Here, we develop an environmentally friendly technology for sterilizing water. The technology bubbles heated un-pressurized carbon dioxide or exhaust gases through wastewater in a bubble column, effectively destroying both bacteria and viruses. The process is extremely cost effective, with no concerning by-products, and has already been successfully scaled-up industrially.

Title: Carbon Dioxide as a Microbial Toxicity Enhancer of Some Antibacterial Agents: A New Potential Water Purification Tool

Author: V. Martirosyan, et al.

Link to full text: https://onlinelibrary.wiley.com/doi/full/10.5402/2012/906761

Abstract: The aim of current paper was to investigate the possibility of increasing the toxicity of calcium hypochlorite (Ca(ClO)₂) and hydrogen peroxide (H₂O₂) on Escherichia coli K-12 by preliminary enrichment of culture media by carbon dioxide (CO₂). For this purpose, the microbes sensitivity to H₂O₂ or/and Ca(ClO)₂ at normal and CO₂-enriched medium was studied by spectrophotometric, radioisotopic, and electronmicroscopic methods. Ten-minute preincubation in CO₂-enriched medium enhanced the toxic effect of both H₂O₂ or/and Ca(ClO ₂ on bacteria as a result of induced growth inhibition, compared to no-CO2 enriched group. Additionally, changes in cell morphology and proliferation were observed. It was demonstrated that the preliminary incubation of microbes in CO₂-enriched culture media in no supercritical concentration elevate the toxic effect of H₂O₂ or/and Ca(ClO)₂ on microbes. This can serve as a novel, effective, inexpensive, and environmentally friendly approach for water purification from bacteria, further improving the protection of the environment and human health.

Title: Carbon dioxide inhibits the growth rate of Staphylococcus aureus at body temperature

Author: M. Persson, et al.

Link to full text: https://pubmed.ncbi.nlm.nih.gov/15529188/

Abstract:

Background: Since the 1930s, carbon dioxide CO₂ has been combined with cold storage for the preservation of food. However, its use for the prevention of surgical wound infection was long considered to be impractical. Now CO₂ is widely used during laparoscopic procedures, and a method has been developed to create a CO₂ atmosphere in an open wound. The aim of this study was to investigate the effect of CO₂ on the growth of Staphylococcus aureus at body temperature.

Methods: First, S. aureus inoculated on blood agar were exposed to pure CO₂ (100%), standard anaerobic gas (5% CO₂, 10% hydrogen, 85% nitrogen), or air at 37 degrees C for a period of 24 h; then a viable count of the bacteria was made. Second, S. aureus inoculated in brain-heart infusion broth and kept at 37 degrees C were exposed to CO₂ or air for 0, 2, 4, 6, and 8 h; then the optical density of the bacteria was measured.

Results: After 24 h, the number of S. aureus on blood agar was about 100 times lower in CO₂ than in anaerobic gas (p = 0.001) and about 1,000 times lower than in air (p = 0.001). Also, in broth, there were fewer bacteria with CO₂ than with air (p < 0.01). After 2 h, the number of bacteria was increased with air (p < 0.001) but not with CO₂ (p = 0.13). After 8 h, the optical density had increased from zero to 1.2 with air but it had increased only to 0.01 with CO₂ (p = 0.001).

Conclusion: Pure CO₂ significantly decreased the growth rate of S. aureus at body temperature. The inhibitory effect of CO₂ increased exponentially with time. Its bacteriostatic effect may help to explain the low infection rates in patients who undergo laparoscopic procedures.