Microbiology vs CO2 Incubators

Know when to use which device and how to get the best deal that keeps meeting your needs

Lab samples get more precious by the year—maybe by the month or week in some cases—and scientists need tools that protect their investment in time and resources. That often requires an incubator. A microbiology incubator keeps organisms at a specific temperature in the ambient air, and a CO2 incubator also balances the pH of the culture.

“The most common application for CO₂ incubators is mammalian cell culture, which is what the vast majority of our customers use them for,” says Scott M. Christensen, vice president of North American sales at NuAire (Plymouth, Minn.).

For a microbiology incubator, says Konrad Knauss, global product manager, Thermo Fisher Scientific (Waltham, Mass.), “target areas are: bacterial/yeast research, microbiology, food and beverage testing, stability testing, wastewater testing, media storage and hatching of insects/fish.”

Features worth seeking

When shopping for a new incubator, many features should be considered, but temperature is the key, particularly uniformity and stability. The former, says Knauss, “shows the user how accurate the temperature distribution is within the incubator chamber—for example, the upper-right corner versus the lower-left corner.” He adds that temperature uniformity is “important to ensure that all samples are exposed to the same exact environment to get comparable results.”

Scientists need special tools like incubators to keep cultures safe for many reasons—from developing new medicines to analyzing biological intricacies, like these lung-cell cilia. (Image courtesy of Jerome Carpenter and Sheel Shah, University of North Carolina at Chapel Hill.)

Temperature stability, says Knauss, “shows the user how accurate the incubator can keep the temperature over time.” He adds, “It’s important to ensure that the desired test temperature is kept safely with not too much of a deviation, and some microbes or samples require tighter temperature specifications than others.”

The recovery of the temperature after opening an incubator also matters. “For a microbiological incubator, how fast does the temperature recover to the set temperature after the door is closed?” Asks MaryKay Bates, cell culture specialist at Thermo Fisher Scientific. “This should be a defined time period where the door is opened, most commonly 15 or 30 seconds.” She adds, “For a CO₂ incubator, look for not only temperature but also CO₂ and humidity recovery.”

If the temperature deviates outside the desired range, the culture could die. So get a device that lets you know if that happens. The device should also make it easy for a scientist to document any changes in temperature over the course of an experiment. “An access port to insert independent probes for keeping track of the actual temperature during the experiment is very useful,” Knauss says. “Inserting probes via the door can have a negative impact on temperature performance.”

Bates even suggests dual-temperature probes in a CO₂ incubator. “A secondary probe checks the first probe, preventing overheating in event of a failure of the primary probe,” she says.

For humidity, Dan T. Simionescu, Harriet and Jerry Dempsey Professor of Bioengineering and director of the Biocompatibility and Tissue Regeneration Laboratories at Clemson University in South Carolina, and his colleagues simply keep a container of water in the incubator, “but it can evaporate quickly,” he says. “Also we do not have a system to measure humidity.” So he uses a portable humidity gauge in the incubator. If he was shopping for a new incubator, he says, he’d want one that would “ensure control and measurement of humidity.”

The need for humidity control can depend on the application, so it is not always required. To get an incubator that is the most future-proof, humidity control is a good option to consider.

To make an incubator easier to use on a daily basis, says Dempsey, get one that “includes independent access to compartments, such as doors for access to each shelf.”

Most labs also want an incubator that can be maintained in-house, at least in most cases. “Systems that require a ‘biomed technician’ to calibrate or maintain because of their complex controls highly increase your costs for service and maintenance,” says Michael Partington, owner of Apex Laboratory Equipment (Red Wing, Minn.). To avoid that situation, he says, “check the OM manuals.” Likewise, that question about expertise can be used to explore another trouble spot that Partington points out: the inability to reach a live serviceperson over the phone to help solve a problem. So he recommends that any potential customer tries calling a company before buying.

Killing contamination

“Cleaning is very important when using an incubator,” says Knauss. For a microbiological incubator, stainless steel is the preferred interior (over plastic), because it resists cleaning agents without oxidizing, and rounded edges prevent dirt from collecting in crevices, which allows easy cleaning, according to Knauss. “For a CO2 incubator, stainless steel or 100% pure copper are both excellent choices for easy care,” he says.

Dempsey agrees on the value of an easily cleaned incubator, and he recommends buying one that “allows for rapid and automatic decontamination using chemicals, UV or other means.” That ensures a clean environment between uses.

Some incubators include features that continuously fight contamination. “Passive contamination control options are a great way to protect cells 24 hours per day, 7 days per week,” Bates explains. “HEPA filtration will capture all contaminants regardless of size, and when the time limit is up, can be autoclaved with other laboratory biological waste and then discarded in normal laboratory trash.” She adds, “Naturally easy to maintain, pure copper [lining] lasts the life of the incubator and eliminates the need for hazardous chemicals, but effectiveness correlates with purity, so look for only 100% pure copper, not an alloy.”

Reducing overhead

In addition to keeping cultures safe, scientists want an affordable solution, and that starts at the beginning. “Get the system delivered and installed with proper calibration included when purchasing,” Partington says. Then, keep the incubator—microbiology or CO₂—working at its best. To do that, says Partington, “Get an annual preventative-maintenance agreement to include changing filter and annual calibration—$100 to $150 a year average cost per chamber.”

Following this advice, says Partington, “will allow you as a customer to focus on your research and using the equipment, rather than all the frustration of trying to find someone who can help you at the last minute when your research samples are in jeopardy.”

Mike May is a freelance writer and editor living in Florida. He can be reached at [email protected].