Harnessing bacterial processes for sustainable metal manufacturing
Traditional metal processing in industrial settings has long faced challenges including high energy consumption, use of hazardous chemicals, and material damage from heat. Now, bacteria are gaining attention as eco-friendly solutions to these problems. In the case of copper, this remarkable biological process uses Acidithiobacillus ferrooxidans bacteria to create microstructures thinner than a human hair. This technology represents more than mere scientific curiosity—it's a revolutionary approach showcasing the future of sustainable manufacturing.
Uses bacterial metabolism instead of high-energy processes
Eliminates hazardous chemicals from the manufacturing process
Creates structures smaller than a human hair width
The core principle of bio-machining is based on redox reactions commonly found in nature. Acidithiobacillus ferrooxidans is a chemolithoautotrophic iron-oxidizing bacterium known for its ability to oxidize iron, using the same mechanism in copper processing 3 .
These bacteria obtain energy needed for the process by oxidizing ferrous ions (Fe²⁺) to ferric ions (Fe³⁺) 3 . The resulting ferric ions act as powerful oxidizers, converting metallic copper (Cu⁰) to copper ions (Cu²⁺) 3 . These copper ions dissolve into the solution, effectively removing material from the metal surface 3 .
Fe²⁺
Bacteria
Fe³⁺
Copper Dissolution
The most remarkable aspect of this process is its infinitely cyclic, self-sustaining system. While oxidizing copper, ferric ions (Fe³⁺) are reduced back to ferrous ions (Fe²⁺), and the bacteria re-oxidize these reduced iron ions to repeat the process 3 . This cyclic structure means the process can be maintained without continuous addition of external chemicals, as long as the bacterial culture environment is properly maintained.
The biggest challenge of bio-machining technology has been its relatively low Material Removal Rate (MRR) compared to conventional processes. To address this, a joint research team from Indonesia and Korea (Indianto, Santoso, Istiyanto, Tae Jo Ko) systematically studied the effect of oxygen supply on bacteria's copper removal capability 6 .
The research team used the following systematic experimental method:
Acidithiobacillus ferrooxidans was cultured in standard 9K medium to establish a healthy bacterial community.
Established an experimental group with an air supply system and a control group without added air 6 .
Copper specimens were exposed to both communities for a set time to observe machining effects.
Quantitatively measured material removal rate and surface roughness to compare differences between the two groups 6 .
The research team observed remarkable results showing that material removal rate increased by approximately 4 times on average with the addition of air (oxygen) 6 . This is because oxygen plays a critical role in maximizing metabolic activity for Acidithiobacillus ferrooxidans, which performs aerobic metabolism 6 .
Material Removal Rate Increase
Surface Roughness Increase
Relative performance comparison of bio-machining with and without air supply
This discovery represents a groundbreaking advancement that significantly increases the commercial applicability of bio-machining. However, surface roughness also increased by approximately 2 times with oxygen addition 6 , suggesting that additional processing may be needed for specific applications.
To better understand the copper material removal characteristics of bio-machining, let's compare it with other research results.
| Indianto et al. 6 | Air supply added | Approximately 2x increase (quantitative value unknown) | Significantly improved material removal rate |
| Jadhav et al. 3 | Supernatant volume, agitation speed control | 0.4 ~ 1.4 μm | Process parameter optimization |
| Eskanadarian et al. 3 | Glucose oxidase used, 24 hours | Approximately 6.7 μm | Alternative pathway using enzymes |
| Johnson et al. 3 | 48 hours machining | 1.7 ~ 2.4 μm | Long-duration machining |
| Xenofontos et al. 3 | B1 strain used, angle adjustment, 24 hours | 5 ~ 8 μm | Effect of strain characteristics and mechanical settings |
Relative surface roughness values across different bio-machining studies
Implementing the bio-machining process requires several essential elements. Below are the main tools and materials used in this process.
| Acidithiobacillus ferrooxidans | Catalyzes copper oxidation and iron reduction | Core machining agent |
| 9K Medium | Provides essential nutrients to bacteria | Maintains bacterial survival and activity |
| Air Supply System | Enhances bacterial metabolic activity | Maximizes material removal rate 6 |
| pH Measurement Equipment | Monitors medium environment | Ensures process stability |
| Temperature Control System | Maintains optimal bacterial activity environment | Improves process efficiency and reproducibility |
This chemolithoautotrophic bacterium is the workhorse of copper bio-machining, capable of oxidizing both iron and sulfur compounds to obtain energy.
Specially formulated medium providing essential nutrients including iron sulfate as an energy source for optimal bacterial growth and activity.
While bio-machining technology is still in the development stage, it shows application potential in fields such as MEMS sensors, micro heat exchangers, and biochips 3 6 . The case applied to micro heat exchangers is particularly impressive. Research indicates that the rough surface generated by bio-machining can enhance heat transfer efficiency 3 . In fact, when copper-based microchannel heat exchangers were manufactured using bio-machining, the potential to replace conventional milling methods was confirmed 3 .
Bio-machining enables precise micro-structuring for advanced sensor applications
Enhanced surface roughness improves heat transfer efficiency in compact systems
Precision microfluidic channels for medical diagnostics and research
Copper processing technology using bacteria is living proof of what's possible when science learns from nature. This technology represents more than just a metal processing method—it will become the foundation for future industries enabling clean energy, resource circulation, and advanced medical technologies. This wise approach utilizing nature's principles shows us the path toward a more sustainable future.
References will be added here in the appropriate format.